Soldering flux and soldering paste

Abstract

The flux of the present invention is characterized by containing rosin, a solvent, a thixotropic agent, an amine hydriodate, and an active agent (excluding amine hydriodates), and the amine hydriodate contains a heteroalicyclic amine hydriodate. The heteroalicyclic amine hydriodate is preferably selected from at least one of piperidine hydriodate and methyl piperidine hydriodate. According to this flux, the occurrence of voids during soldering 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. 2022-117441 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, in the embodiment of Patent Document 1, a solder paste is proposed, which uses a flux containing a base resin, a solvent, a thixotropic agent, an activator (amine hydrobromide, organic monocarboxylic acid), 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] In recent years, miniaturized components such as QFN (Quad Flat Non-Leaded Package) have been used. QFN does not have leads around the package, but has an exposed surface of the lead frame and electrode terminals on the back of the package. Therefore, when the QFN is soldered to the substrate, the back of the QFN is joined to the surface of the substrate using solder paste.

[0012] When the exposed surface of the lead frame and the electrode terminals on the rear surface of such a package are soldered to a substrate, it is difficult to sufficiently suppress the generation of voids with conventional solder pastes.

[0013] Therefore, an object of the present invention is to provide a flux that can further suppress the generation of voids during soldering, and a solder paste using the flux.

[0014] Means of solving the problem

[0015] In order to solve the above-mentioned problems, the present invention adopts the following configuration.

[0016] [1] A soldering flux comprising rosin, a solvent, a thixotropic agent, an amine hydroiodide and an activator (except the amine hydroiodide), wherein the amine hydroiodide comprises a heteroalicyclic amine hydroiodide.

[0017] [2] The soldering flux according to [1], wherein the heteroalicyclic amine hydroiodide is at least one selected from piperidine hydroiodide and methylpiperidinium hydroiodide.

[0018] [3] The soldering flux according to [1] or [2], wherein the content of the heteroalicyclic amine hydroiodide is 0.01% by mass or more and 1.5% by mass or less relative to the total mass (100% by mass) of the soldering flux.

[0019] [4] The soldering flux according to any one of [1] to [3], wherein the solvent is a combination of 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.

[0020] [5] The soldering flux according to [4], wherein the ratio of the solvent (S1) to the solvent (S3) is 50 / 50 or more and 85 / 15 or less in terms of a mass ratio represented by solvent (S1) / solvent (S3).

[0021] [6] The soldering flux according to any one of [1] to [5], further comprising a sulfur-containing compound.

[0022] [7] The soldering flux according to any one of [1] to [6], wherein the activator contains a dicarboxylic acid represented by the following general formula (A0).

[0023] [Chemical formula 1]

[0024]

[0025] [Wherein, n is an integer from 0 to 8.]

[0026] [8] The soldering flux according to any one of [1] to [7], wherein the activator contains a triazole compound.

[0027] [9] A solder paste comprising a solder alloy powder and the flux according to any one of [1] to [8].

[0028] Effects of the Invention

[0029] According to the present invention, it is possible to provide a flux that can further suppress the generation of voids during soldering, and a solder paste using the flux. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] 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

[0031] (Flux)

[0032] The soldering flux of this embodiment contains rosin, a solvent, a thixotropic agent, an amine hydroiodide, and an activator (except the amine hydroiodide). The amine hydroiodide contains alicyclic amine hydroiodide.

[0033] <Rosin>

[0034] 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.

[0035] 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.

[0036] The rosin may be used alone or in combination of two or more.

[0037] As the rosin, among the above, at least one selected from polymerized rosin, acid-modified hydrogenated rosin and hydrogenated rosin is preferably used.

[0038] As the acid-modified hydrogenated rosin, acrylic acid-modified hydrogenated rosin is preferably used.

[0039] 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.

[0040] 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).

[0041] <Solvent>

[0042] Examples of the solvent include water, alcohol solvents, glycol ether solvents, and terpineols.

[0043] 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.

[0044] 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.

[0045] 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).

[0046] Examples of other solvents include dioctyl sebacate (DOS) and liquid paraffin.

[0047] The solvent may be used alone or in combination of two or more.

[0048] In the soldering flux of this embodiment, from the viewpoint of suppressing the generation of voids during soldering, the solvent preferably uses solvents having different boiling points in combination. Among them, the solvent preferably uses 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. By using the solvent (S1) and the solvent (S3) in combination, the generation of voids during soldering can be further suppressed.

[0049] 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.

[0050] 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).

[0051] 《Solvents with a boiling point of 250°C or higher (S1)》

[0052] 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.

[0053] 《Solvents with a boiling point exceeding 220°C and less than 250°C (S2)》

[0054] 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.).

[0055] 《Solvents with a boiling point below 220°C (S3)》

[0056] 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.

[0057] As a solvent having different boiling points, a combination of the above-mentioned components (S1) and (S3) is preferred. This is because the formation of voids can be easily suppressed during welding, the boiling point is not too low, and the ratio of viscosity change over time when the solder paste is made is low. Therefore, it is particularly preferred to use components (S1) and (S31) in combination.

[0058] When the components (S1) and (S3) are used together, the ratio of the components (S1) to (S3) is preferably 50 / 50 or more and 85 / 15 or less in terms of the mass ratio represented by solvent (S1) / solvent (S3) from the viewpoint of easily suppressing the generation of voids during soldering. Furthermore, from the viewpoint of easily suppressing the ratio of the viscosity change over time when the solder paste is prepared, the mass ratio represented by solvent (S1) / solvent (S3) is preferably 55 / 45 or more and 85 / 15 or less, and more preferably 60 / 40 or more and 85 / 15 or less.

[0059] The total content of solvent is the balance in the flux.

[0060] 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 %.

[0061] <Thixotropic agent>

[0062] Examples of the thixotropic agent include ester-based thixotropic agents, amide-based thixotropic agents, and sorbitol-based thixotropic agents.

[0063] Examples of the ester-based thixotropic agent include ester compounds, and specific examples include hydrogenated castor oil and ethyl myristate.

[0064] Examples of the amide-based thixotropic agent include monoamide, bisamide, and polyamide.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] The thixotropic agent may be used alone or in combination of two or more.

[0072] 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.

[0073] As the ester-based thixotropic agent, hydrogenated castor oil is preferred.

[0074] As the amide-based thixotropic agent, polyamide is preferred.

[0075] 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 %).

[0076] <Amine hydroiodide>

[0077] In the soldering flux of the present embodiment, the amine hydroiodide contains a heteroalicyclic amine hydroiodide. The heteroalicyclic amine hydroiodide is a compound formed by the reaction of a heteroalicyclic amine and hydrogen iodide.

[0078] The heteroalicyclic amine in the heteroalicyclic amine hydroiodide is preferably a heteroalicyclic amine having a 6-membered ring structure, and among these, piperidine and methylpiperidine are preferred, and piperidine and 2-methylpiperidine are particularly preferred.

[0079] As the heteroalicyclic amine hydroiodide, at least one selected from piperidine hydroiodide and methylpiperidine hydroiodide is preferably used, and at least one selected from piperidine hydroiodide and 2-methylpiperidine hydroiodide is more preferably used.

[0080] The content of heteroalicyclic amine hydroiodide in the flux of the present embodiment is preferably 0.01% by mass to 1.5% by mass, more preferably 0.05% by mass to 1.25% by mass, further preferably 0.1% by mass to 1% by mass, and particularly preferably 0.1% by mass to 0.9% by mass, relative to the total mass of the flux (100% by mass).

[0081] When the content of the heteroalicyclic amine hydroiodide is at least the lower limit of the preferred range, the generation of voids during soldering is easily suppressed, and when it is at most the upper limit of the preferred range, the increase in viscosity of the solder paste over time is easily suppressed.

[0082] Among the amine hydroiodides, amine hydroiodides other than the above-mentioned heteroalicyclic amine hydroiodides may be used in combination.

[0083] As amine hydroiodides other than heteroalicyclic amine hydroiodides, for example, chain amine hydroiodides such as monoethylamine hydroiodide (monoethylamine·HI), triethylamine·HI, 1-pentylamine·HI, 2-ethylhexylamine·HI, diallylamine·HI, etc.; alicyclic amine hydroiodides such as cyclohexylamine·HI, etc.; aromatic amine hydroiodides such as aniline·HI, etc.; guanidine hydroiodides such as 1,3-diphenylguanidine·HI, etc. can be cited.

[0084] <Activator>

[0085] Examples of the activator (except the amine hydroiodide salt) include halogen-based activators, organic acids, and amines.

[0086] 《Halogen-based Activators》

[0087] Examples of the halogen-based activating agent include amine hydrohalide salts other than amine hydroiodide salts and organic halogen compounds other than amine hydrohalide salts.

[0088] The halogen-based activators may be used alone or in combination of two or more.

[0089] Amine hydrohalides other than amine hydroiodides:

[0090] 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 bromine, chlorine, and fluorine.

[0091] Examples of the amine hydrohalide salt include amine hydrobromide, amine hydrochloride, and amine hydrofluoride.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] Organic halogen compounds other than amine hydrohalides:

[0096] Examples of the organic halogen compound other than the amine hydrohalide salt include halogenated aliphatic compounds having a halogenated aliphatic hydrocarbon group.

[0097] 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.

[0098] Examples of the halogenated aliphatic compound include halogenated aliphatic alcohols and halogenated heterocyclic compounds.

[0099] 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.

[0100] Examples of the halogenated heterocyclic compound include compounds represented by the following general formula (3).

[0101] R 5 -(R 6 )m···(3)

[0102] R 5 represents an m-valent heterocyclic group. 6 It represents a halogenated aliphatic hydrocarbon group.

[0103] As R 5 The 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.

[0104] 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.

[0105] Specific examples of the halogenated heterocyclic compound include tris-(2,3-dibromopropyl)isocyanurate and the like.

[0106] 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.

[0107] 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.

[0108] 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 %).

[0109] 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.

[0110] Organic Acids

[0111] Examples of the organic acid include monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, cyanuric acid, dimer acid, and trimer acid.

[0112] 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.

[0113] 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.

[0114] Examples of the tricarboxylic acid include citric acid and the like.

[0115] Examples of cyanuric acid include tris(2-carboxyethyl)isocyanurate and the like.

[0116] 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.

[0117] 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.

[0118] The organic acid may be used alone or in combination of two or more.

[0119] As the organic acid contained in the flux of this embodiment, it is preferred to use at least one selected from monocarboxylic acid, dicarboxylic acid and dimer acid, more preferably to use at least one selected from dicarboxylic acid and dimer acid, further preferably to use at least one selected from aliphatic dicarboxylic acid and dimer acid, and particularly preferably to use at least aliphatic dicarboxylic acid.

[0120] In the soldering flux of the present embodiment, from the viewpoint of suppressing the generation of solder balls, the activator preferably contains a dicarboxylic acid represented by the following formula (A0).

[0121] [Chemical formula 2]

[0122]

[0123] [Wherein, n is an integer from 0 to 8.]

[0124] In the formula (A0), n is an integer of 0 to 8, preferably an integer of 2 to 6, more preferably an integer of 3 to 5, and even more preferably 4.

[0125] That is, as the aliphatic dicarboxylic acid, it 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.

[0126] 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 %).

[0127] 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.

[0128] 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.

[0129] "amine"

[0130] Examples of the amine include azoles, guanidines, alkylamine compounds, and amino alcohol compounds.

[0131] 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.;

[0132] 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.

[0133] Examples of the alkylamine compound include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, and stearylamine.

[0134] Examples of the amino alcohol compound include N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine and the like.

[0135] The amines may be used alone or in combination of two or more.

[0136] 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.

[0137] 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.

[0138] 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).

[0139] 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.

[0140] 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.

[0141] In addition, in the soldering flux of this embodiment, from the viewpoint of suppressing the generation of solder balls, it is also preferred to use aliphatic dicarboxylic acids and triazole compounds as the activator, and it is more preferred to use a dicarboxylic acid represented by the general formula (A0) and a triazole compound in combination. When aliphatic dicarboxylic acids and triazole compounds are used in combination, the mixing ratio (mass ratio) of aliphatic dicarboxylic acids and triazole compounds is preferably aliphatic dicarboxylic acids / triazole compounds = 90 / 10 or more and 95 / 5 or less.

[0142] <Other ingredients>

[0143] The soldering flux of the present embodiment may contain other components as necessary in addition to the rosin, the solvent, the thixotropic agent, the amine hydroiodide, and the activator.

[0144] Examples of other components include sulfur-containing compounds, resin components other than rosin, surfactants, antioxidants, metal deactivators, and silane coupling agents.

[0145] Sulfur compounds

[0146] The soldering flux of the present embodiment may further contain a sulfur-containing compound. By further containing a sulfur-containing compound, the effect of suppressing the change in viscosity of the solder paste over time is easily enhanced.

[0147] As the sulfur-containing compound here, for example, preferably, a thiol compound is mentioned, and among them, a thiol compound (Tp) having a thiophenol skeleton is more preferred.

[0148] 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).

[0149] About Thiol Compounds (Tp):

[0150] As the thiol compound (Tp), for example, a thiol compound represented by the following general formula (Tp-0) is preferably mentioned.

[0151] [Chemical formula 3]

[0152]

[0153] [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.]

[0154] 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.

[0155] Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

[0156] The alkyl group may be linear or branched, and is preferably an alkyl group having 1 to 6 carbon atoms.

[0157] The alkoxy group is preferably an alkoxy group having 1 to 6 carbon atoms.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] Preferred examples of the thiol compound (Tp) include aminothiophenol represented by the following chemical formula (Tp-10).

[0163] [Chemical formula 4]

[0164]

[0165] 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-).

[0166] The thiol compound (Tp) may be used alone or in combination of two or more.

[0167] As the thiol compound (Tp), 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 1 or more, y is 1 or more) and thiophenol (x is 1 or more, y=0) are more preferred.

[0168] Among these compounds, from the viewpoint of more easily improving the effect of suppressing the time-dependent viscosity change of the solder paste, 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 the combined use of 2-aminothiophenol (x=y=1) and 4-aminothiophenol (x=y=1) is particularly preferred.

[0169] 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.

[0170] When the flux of the present embodiment contains a thiol compound (Tp), the total content of the thiol compound (Tp) is preferably 0.005 mass % to 0.7 mass % inclusive, more preferably 0.01 mass % to 0.5 mass % inclusive, and further preferably 0.02 mass % to 0.3 mass % inclusive, relative to the total mass (100 mass %) of the flux.

[0171] When the total content of the thiol compounds (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.

[0172] When the soldering flux of the present embodiment contains a thiol compound (Tp) in addition to the above-mentioned amine hydroiodide, the mixing ratio (mass ratio) of the amine hydroiodide and the thiol compound (Tp) exceeds thiol compound (Tp) / amine hydroiodide = 50 / 50, 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.

[0173] Regarding thiol compounds other than compound (Tp):

[0174] As the thiol compound, thiol compounds other than the above-mentioned compound (Tp) may be used.

[0175] 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.

[0176] Regarding sulfur-containing compounds other than mercaptan compounds:

[0177] Sulfur-containing compounds other than thiol compounds may be used as the sulfur-containing compound.

[0178] 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.

[0179] 《Resin ingredients other than rosin》

[0180] 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.

[0181] 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.

[0182] Surfactants

[0183] Examples of the surfactant include nonionic surfactants and weak cationic surfactants.

[0184] 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.

[0185] Examples of the weak cationic surfactant include terminal diamine polyethylene glycol, terminal diamine polyethylene glycol-polypropylene glycol copolymers, aliphatic amine polyoxyethylene adducts, aromatic amine polyoxyethylene adducts, and polyamine amine polyoxyethylene adducts.

[0186] 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.

[0187] In the soldering flux of the present embodiment described above, since it contains a specific amine hydroiodide containing heteroalicyclic amine hydroiodide, when used in solder paste, the generation of voids during soldering can be further suppressed. The reason for this effect is not clear, but it is speculated that in the case of heteroalicyclic amine hydroiodide, since the imino group (-N-) constitutes a part of the alicyclic ring, the imino group (-N-) faces the outside of the molecule, the interaction with other flux components or solder alloy is high, and the soldering effect is relatively strong.

[0188] The flux of this embodiment preferably contains a sulfur-containing compound in addition to the specific amine hydroiodide containing heteroalicyclic amine hydroiodide, whereby the solder paste containing the flux can more easily suppress the generation of voids during soldering and also suppress the viscosity change of the solder paste over time.

[0189] (Solder Paste)

[0190] The solder paste of the present embodiment contains solder alloy powder and the above-mentioned flux.

[0191] 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.

[0192] In addition, the solder alloy powder can also be composed of powder of Sn-Pb system or solder alloy formed by adding Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. to the Sn-Pb system.

[0193] The solder alloy powder is preferably a solder that does not contain Pb.

[0194] As the solder alloy powder, for example, a solder alloy powder having a melting temperature of 150 to 250° C. can be used.

[0195] 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.

[0196] In the solder paste of the present embodiment described above, since the flux containing amine hydroiodide is used, the generation of voids during soldering can be suppressed.

[0197] Furthermore, in the solder paste of the present embodiment, when a flux containing a sulfur compound is further used in combination, more preferably when a flux containing a specific thiol compound is further used in combination, the generation of voids during soldering is suppressed and the viscosity change over time is less likely to occur.

[0198] Example

[0199] Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to the following examples.

[0200] <Preparation of flux>

[0201] (Examples 1 to 60, Comparative Examples 1 to 12)

[0202] The fluxes of Examples and Comparative Examples were prepared by mixing and blending the components according to the compositions shown in Tables 1 to 9. The blending components used are shown below.

[0203] rosin:

[0204] As the rosin, acrylic acid-modified hydrogenated rosin or hydrogenated rosin was used.

[0205] Solvent:

[0206] As the solvent (S1) having a boiling point of 250°C or higher, diethylene glycol mono-2-ethylhexyl ether (boiling point 272°C) and diethylene glycol mono-hexyl ether (hexyl diglycol) (boiling point 258°C) were used.

[0207] 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.

[0208] Solvent (S31) having a boiling point of 190°C or higher and 220°C or lower:

[0209] 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)

[0210] Solvents with a boiling point of 160°C or more and less than 190°C (S32):

[0211] Ethylene glycol monobutyl ether (butyl glycol) (boiling point 171°C), 2,3-butanediol (boiling point 183°C)

[0212] Thixotropic agent:

[0213] As the thixotropic agent, polyamide and hydrogenated castor oil were used.

[0214] Amine hydroiodide:

[0215] As heteroalicyclic amine hydroiodide, 2-methylpiperidine·HI and piperidine·HI were used.

[0216] As other amine hydroiodides, monoethylamine·HI, triethylamine·HI, aniline·HI, cyclohexylamine·HI, 1,3-diphenylguanidine·HI, diallylamine·HI, 1-pentylamine·HI, and 2-ethylhexylamine·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] Sulfur compounds:

[0221] As the sulfur-containing compound, a thiol compound (Tp) having a thiophenol skeleton shown below was used.

[0222] Thiol compounds with a thiophenol skeleton (Tp):

[0223] 2-Aminothiophenol and 4-Aminothiophenol

[0224] Active Agent:

[0225] As the activator, the following amine hydrobromide, amine hydrochloride, organic acid, and amine were used.

[0226] As the amine hydrobromide, 2-methylpiperidine·HBr, piperidine·HBr, and 1,3-diphenylguanidine·HBr were used.

[0227] As the amine hydrochloride, 1,3-diphenylguanidine·HCl was used.

[0228] The amine hydrobromide and amine hydrochloride are used as finished products.

[0229] Organic Acids:

[0230] As the organic acid, hydrogenated dimer acid, adipic acid, benzoic acid, and phenylsuccinic acid were used.

[0231] amine:

[0232] As the amine, 1,3-di-o-tolylguanidine and 3-(N-salicyloyl)amino-1,2,4-triazole were used.

[0233] Other Ingredients:

[0234] As the acrylic resin, ethylene-acrylic acid copolymer was used.

[0235] As an antioxidant, 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol] was used.

[0236] <Preparation of Solder Paste>

[0237] 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.

[0238] Solder Alloy Powder:

[0239] 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.

[0240] 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).

[0241] <Evaluation>

[0242] Using the solder paste prepared as described above, evaluations of [the effect of suppressing the generation of voids] and [the change in viscosity of the solder paste over time] were performed according to the test methods described below.

[0243] [Effect of suppressing void generation]

[0244] (1) Test method

[0245] 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).

[0246] 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.

[0247] Next, reflow is performed to perform soldering.

[0248] The reflow curve at this time is as follows Figure 1 shown.

[0249] 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.

[0250] 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).

[0251] The void area is measured when X-rays pass through at least one void, which is considered to be a void. Voids with a diameter of 0.1 μm or more are detected.

[0252] 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 1 to 9.

[0253] (2) Evaluation criteria

[0254] 1 point: The void area ratio is less than 10%.

[0255] 2 points: The void area ratio is 10% or more and less than 15%.

[0256] 3 points: The void area ratio is 15% or more and less than 20%.

[0257] 4 points: The void area ratio is 20% or more and less than 30%.

[0258] 5 points: The void area ratio is 30% or more.

[0259] [Changes in Viscosity of Solder Paste over Time]

[0260] (1) Test method

[0261] 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 5 to 9.

[0262] (2) Evaluation criteria

[0263] 1 point: The viscosity change rate after 24 hours was less than 10%.

[0264] 2 points: The viscosity change rate after 24 hours is 10% or more and less than 20%.

[0265] 3 points: The viscosity change rate after 24 hours is 20% or more and less than 30%.

[0266] 4 points: The viscosity change rate after 24 hours is 30% or more and less than 40%.

[0267] 5 points: The viscosity change rate after 24 hours is 40% or more and less than 50%.

[0268] 6 points: The viscosity change rate after 24 hours is 50% or more.

[0269] [Table 1]

[0270]

[0271] [Table 2]

[0272]

[0273] [Table 3]

[0274]

[0275] [Table 4]

[0276]

[0277] From the results shown in Tables 1 to 4, it can be confirmed that the flux of the examples containing heteroalicyclic amine hydroiodide has a lower void area ratio than the flux of the comparative examples containing amine hydrohalide salts that are not heteroalicyclic amine hydroiodide, and is more effective in suppressing the generation of voids during welding (comparison between Examples 2 and 6 and Comparative Examples 1 to 12).

[0278] [Table 5]

[0279]

[0280] From the results shown in Table 5, it was confirmed that the further inclusion of a thiol compound (Tp) can suppress the generation of voids during soldering and that the viscosity change over time when the solder paste is prepared is less likely to occur.

[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 23 to 60 using alicyclic amine hydroiodide and a thiol compound (Tp) in combination are used, the generation of voids during soldering can be suppressed and the viscosity change over time when prepared as solder paste is unlikely to occur.

[0290] 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, an amine hydroiodide and an activator (except the amine hydroiodide), The amine hydroiodide contains heteroalicyclic amine hydroiodide, and the heteroalicyclic amine hydroiodide is at least one selected from piperidine hydroiodide and methylpiperidine hydroiodide. The content of the heteroalicyclic amine hydroiodide is 0.01 mass % or more and 1.5 mass % or less relative to the total mass (100 mass %) of the soldering flux.

2. The soldering flux according to claim 1, wherein The solvent used is 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.

3. The soldering flux according to claim 2, wherein: The ratio of the solvent (S1) to the solvent (S3) is 50 / 50 or more and 85 / 15 or less in terms of a mass ratio represented by solvent (S1) / solvent (S3).

4. The soldering flux according to claim 1, wherein The soldering flux also contains a sulfur-containing compound.

5. The soldering flux according to claim 1, wherein The active agent contains a dicarboxylic acid represented by the following general formula (A0): [Chemical formula 1] In the formula, n is an integer from 0 to 8.

6. The soldering flux according to claim 1, wherein The active agent contains a triazole compound.

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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