Flux and method for producing joined body

Abstract

A flux containing a rosin component, an activator, and water is adopted. The activator includes an imidazole compound, and the amount of water is 40% by mass or more with respect to a total mass of the flux. The molar ratio of the imidazole compound to the rosin component is 1.3 or more as a molar ratio represented by the imidazole compound / the rosin component.

Description

Flux and method for manufacturing joint body

[0001] This application claims priority to Japanese Patent Application No. 2023-128560, filed August 7, 2023, the contents of which are incorporated herein by reference.

[0002] Attaching components to a substrate and electrically connecting the components to the substrate are generally performed by soldering, which uses flux, solder, or a solder paste made by mixing flux and solder.

[0003] Flux chemically removes metal oxides present on the metal surfaces of the objects to be soldered and in the solder, allowing the migration of metal elements at the interface between the two. Therefore, when soldering is performed using flux, an intermetallic compound is formed between the two, resulting in a strong bond. Such fluxes generally contain resin components, solvents, activators, thixotropic agents, etc.

[0004] In soldering, methods such as flow soldering and reflow soldering are used depending on the size of the objects to be joined. In flow soldering, flux is first applied to the soldering surface of a board on which components are mounted. Next, while the board on which components are mounted is being transported, molten solder is jetted from below and brought into contact with the soldering surface, thereby performing soldering. In reflow soldering, solder paste is first printed on the board. Next, components are mounted, and the board on which components are mounted is then heated in a heating furnace called a reflow furnace, thereby performing soldering.

[0005] Generally, liquid fluxes used in flow soldering are produced by dissolving a resin component such as rosin and an activator in 2-propanol or ethanol. However, from the viewpoint of environmental protection, there is a need to reduce the emissions of 2-propanol and ethanol. Therefore, fluxes in which the main solvent is replaced with water (hereinafter referred to as water-based fluxes) have been proposed.

[0006] It is difficult for water-based fluxes to dissolve hydrophobic materials such as rosin. To address this issue, water-based fluxes have been proposed in which rosin is saponified using, for example, lower amines or ammonia (Patent Document 1).

[0007] Japanese Patent Application Publication No. 8-132282

[0008] However, in the water-based flux described in Patent Document 1, the lower amines and ammonia contained in the flux volatilize and emit an odor, which causes a problem of worsening the working environment for users of the flux.

[0009] Therefore, an object of the present invention is to provide a flux that has sufficient solubility for hydrophobic components such as rosin even when water is used as a main solvent and has a reduced odor, and a method for producing a bonded body using the flux.

[0010] The present invention includes the following aspects: [1] A flux containing a rosin component, an activator, and water, wherein the activator contains an imidazole compound, the content of the water is 40 mass% or more relative to the total mass (100 mass%) of the flux, and the molar ratio of the imidazole compound to the rosin component, expressed as the molar ratio of imidazole compound / rosin component, is 1.3 or more. [2] The flux according to [1], wherein the rosin component contains at least one of an acid-modified rosin and an acid-modified hydrogenated rosin. [3] The flux according to [1] or [2], wherein the molar ratio of the imidazole compound to the rosin component, expressed as the molar ratio of imidazole compound / rosin component, is 1.8 or more and 20 or less. [4] The flux according to any one of [1] to [3], further comprising an activator other than an imidazole compound, wherein the ratio (mass ratio) of the total content of the imidazole compound and the rosin component to the content of the activator other than the imidazole compound is 2 or more. [5] The flux according to [1], further comprising a solvent having a melting point of 30°C or higher. [6] The flux according to [5], wherein the rosin component includes at least one of an acid-modified rosin and an acid-modified hydrogenated rosin. [7] The flux according to [4], wherein the activator other than the imidazole compound is at least one selected from the group consisting of an organic acid, an amine other than an imidazole compound, and a halogen compound. [8] The flux according to any one of [1] to [7], wherein the imidazole compound is a compound represented by the general formula (IZ0) described below. [9] A method for producing a bonded body, comprising the step of soldering a solder alloy to a surface of a substrate treated with the flux according to any one of [1] to [8], to obtain a bonded body.

[10] The manufacturing method according to [9], further comprising a step of attaching a component to the substrate before treating the surface of the substrate with the flux, wherein the bonded body is formed by bonding the component and the substrate.

[0011] According to the present invention, it is possible to provide a flux that sufficiently dissolves hydrophobic components such as rosin even when water is used as a main solvent and has a reduced odor, and a method for producing a bonded body using the flux.

[0012] A preferred embodiment of the present invention is described below. The following description is provided for a more complete understanding of the gist of the invention and does not limit the present invention unless otherwise specified. For example, unless otherwise specified, conditions such as materials, amounts, types, numbers, positions, and ratios may be changed, added, or omitted as necessary. (Flux) The flux according to this embodiment essentially contains a rosin component, an activator, and water. The activator contains at least an imidazole compound. The water content is 40% by mass or more relative to the total mass (100% by mass) of the flux. The molar ratio of the imidazole compound to the rosin component, expressed as the molar ratio of imidazole compound / rosin component, is 1.3 or more. The flux according to this embodiment is suitable for use in flow soldering.

[0013] As used herein, the melting point refers to the temperature at which a solid melts and becomes liquid. The melting point of the target compound may be, for example, the melting point listed in the "Iwanami Dictionary of Physics and Chemistry, 5th Edition." Alternatively, the melting point of the target compound may be the melting point measured by a method in accordance with JIS K 0064:1992.

[0014] In this specification, the solid content of the flux refers to all components remaining in the flux, excluding the solvent. The solid content of the flux may be 1.0% by mass or more but less than 60% by mass, preferably 1.0% by mass or more but less than 50% by mass, more preferably 2.0% by mass or more but less than 45% by mass, and even more preferably 3.0% by mass or more but less than 40% by mass, relative to the total mass (100% by mass) of the flux. If necessary, it may be 5.0% by mass or more but less than 40% by mass, 8.0% by mass or more but less than 30% by mass, 10% by mass or more but less than 25% by mass, or 15% by mass or more but less than 20% by mass. Examples of materials preferably contained in the flux are described below.

[0015] <Rosin Component> The flux according to this embodiment contains a rosin component. The rosin component can be selected arbitrarily, but includes at least one of abietic acid, an isomer of abietic acid, and a chemically modified abietic acid. In the present invention, the term "rosin component" encompasses natural resins containing abietic acid as the main component and a mixture of abietic acid and its isomers, purified rosin derived from natural resins, and chemically modified natural resins or purified rosins (sometimes referred to as rosin derivatives).

[0016] The total content of abietic acid and abietic acid isomers in the natural resin is, for example, 40% by mass or more and 80% by mass or less relative to the natural resin. For example, it may be 50% by mass or more and 75% by mass or less, or 60% by mass or more and 70% by mass or less. In this specification, the term "main component" refers to a component that constitutes a compound and whose content in the compound is 40% by mass or more.

[0017] Representative isomers of abietic acid include neoabietic acid, palustric acid, levopimaric acid, etc. The structure of abietic acid is shown below.

[0018]

[0019] Examples of the "natural resin" include gum rosin, wood rosin, tall oil rosin, etc. Examples of trees from which the natural resin is derived include Pinus massoniana, Slash pine (Pinus elliottii), Merkusii pine (Pinus merkusii), Caribbean pine (Pinus caribaea), Pinus kesiya, Loblolly pine (Pinus taeda), and Great King pine (Pinus palustris).

[0020] Purified rosin is obtained by purifying natural resins using known methods. Hereinafter, natural rosin and purified rosin are collectively referred to as unmodified rosin. Purified rosin can be obtained using various known means. Specific examples of purification methods include distillation, extraction, recrystallization, and adsorption.

[0021] Rosin derivatives can be obtained from unmodified rosin by known methods. Examples of rosin derivatives include unmodified rosin chemically modified. Examples of rosin derivatives include hydrogenated rosin, disproportionated rosin, polymerized rosin, acid-modified rosin, rosin ester, rosin amine, and rosin phenolic resin. Rosin derivatives include unmodified rosin that has been subjected to one or more treatments selected from the group consisting of hydrogenation, dehydrogenation, neutralization, alkylene oxide addition, amidation, dimerization and multimerization, esterification, and Diels-Alder cycloaddition. Examples of Diels-Alder cycloaddition include a reaction in which an α,β-unsaturated carboxylic acid is added to unmodified rosin.

[0022] Hydrogenated rosin can be obtained, for example, by hydrogenating unmodified rosin using a known method. Disproportionated rosin can be obtained, for example, by heating unmodified rosin in the presence of a disproportionation catalyst (disproportionation) using a known method. Polymerized rosin can be obtained, for example, by polymerizing unmodified rosin using a known method.

[0023] Preferred examples of acid-modified rosin include α,β-unsaturated carboxylic acid-modified rosin (α,β-unsaturated carboxylic acid modified product). α,β-Unsaturated carboxylic acid-modified rosin is obtained by subjecting unmodified rosin to an addition reaction with an α,β-unsaturated carboxylic acid. α,β-Unsaturated carboxylic acid-modified rosin can be obtained by subjecting unmodified rosin melted under heat to Diels-Alder cycloaddition of an α,β-unsaturated carboxylic acid. In this specification, acid-modified rosin may also include unmodified rosin that has been subjected to one or more treatments selected from the group consisting of hydrogenation, dehydrogenation, neutralization, alkylene oxide addition, amidation, dimerization, oligomerization, and esterification, in addition to the Diels-Alder cycloaddition of an α,β-unsaturated carboxylic acid.

[0024] The α,β-unsaturated carboxylic acid is not particularly limited, and examples thereof include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, muconic acid, maleic anhydride, itaconic anhydride, citraconic anhydride, muconic anhydride, maleic acid half ester, fumaric acid half ester, itaconic acid half ester, and the like, with acrylic acid or maleic acid being preferred.

[0025] The rosin ester may be, for example, a reaction product of unmodified rosin and an alcohol. The alcohol is not particularly limited, and may be any known alcohol used in the production of rosin esters.

[0026] The rosin amine may be, for example, a mixture of dehydroabietylamine, dihydroabietylamine, and tetrahydroabietylamine, which may refer to a so-called disproportionated rosin amine. The rosin amine may contain at least one of dehydroabietylamine, dihydroabietylamine, and tetrahydroabietylamine. The structures of dehydroabietylamine, dihydroabietylamine, and tetrahydroabietylamine are shown below.

[0027]

[0028] As described above, examples of rosin derivatives include hydrogenated rosin, polymerized rosin, polymerized hydrogenated rosin, disproportionated rosin, acid-modified rosin, rosin ester, acid-modified hydrogenated rosin, acid anhydride-modified hydrogenated rosin, acid-modified disproportionated rosin, acid anhydride-modified disproportionated rosin, phenol-modified rosin, and α,β-unsaturated carboxylic acid-modified products (acrylic acid-modified rosin, maleic acid-modified rosin, fumaric acid-modified rosin, etc.), as well as purified products, hydrogenated products, and disproportionated products of the polymerized rosins, purified products, hydrogenated products, and disproportionated products of the α,β-unsaturated carboxylic acid-modified products, rosin alcohol, rosin amine, hydrogenated rosin alcohol, hydrogenated rosin ester, rosin soap, hydrogenated rosin soap, and acid-modified rosin soap.

[0029] The rosin component may be used alone or in combination of two or more. The rosin component preferably contains an acid-modified rosin. The rosin component preferably contains one or more selected from the group consisting of acid-modified rosin and acid-modified hydrogenated rosin. The acid-modified rosin is preferably one or more selected from the group consisting of acrylic acid-modified rosin and maleic acid-modified rosin. The acid-modified hydrogenated rosin is preferably one or more selected from the group consisting of acrylic acid-modified hydrogenated rosin and maleic acid-modified hydrogenated rosin.

[0030] It is also preferable that the rosin component has a predetermined acid value. The acid value of the rosin component can be measured as follows. The acid value refers to the number of milligrams of potassium hydroxide required to neutralize the carboxyl groups in 1 g of the sample to be measured. The acid value of the rosin component can be measured, for example, according to 3.1 Neutralization titration method of JIS K 0070 "Test methods for acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponifiable matter of chemical products."

[0031] When the flux according to the present embodiment contains two or more types of rosin components, the acid value of the rosin component means the weighted average of the acid values ​​of all types of rosin components contained in the flux.

[0032] The acid value of the rosin component is, for example, 140 mgKOH / g or more, preferably 200 mgKOH / g or more, more preferably 210 mgKOH / g or more, even more preferably 220 mgKOH / g or more, and particularly preferably 230 mgKOH / g or more. The upper limit of the acid value of the rosin component is not particularly limited, but may be 500 mgKOH / g or less, 400 mgKOH / g or less, or 350 mgKOH / g or less. Depending on the need, the acid value of the rosin component may be 140 to 330 mgKOH / g, 150 to 300 mgKOH / g, 150 to 270 mgKOH / g, or 180 to 250 mgKOH / g. Having an acid value of the rosin component equal to or greater than the lower limit increases the solubility of solids contained in the flux, such as the rosin component, imidazole compound, and activator. Insufficient solubility can result in precipitation of solids. When the acid value of the rosin component is equal to or less than the upper limit, migration in a joint soldered using the flux can be easily suppressed. It is also preferable that the rosin component consists solely of a rosin component having an acid value of 200 mgKOH / g or more.

[0033] The content of the rosin component in the flux is preferably 0.5% by mass to 30% by mass, more preferably 1.0% by mass to 20% by mass, and even more preferably 2.0% by mass to 9.0% by mass, relative to the total mass (100% by mass) of the flux. If necessary, it may be 1.5% by mass to 25% by mass, 3.0% by mass to 15% by mass, or 5.0% by mass to 10% by mass.

[0034] The rosin content of the solids in the flux is preferably 5.0% by mass to 90% by mass, more preferably 6.5% by mass to 75% by mass, and even more preferably 8.0% by mass to 60% by mass, based on the total solids (100% by mass). If necessary, it may be 10% by mass to 80% by mass, 20% by mass to 70% by mass, 30% by mass to 60% by mass, or 40% by mass to 50% by mass. The molecular weight of the rosin component can be selected arbitrarily, but may be, for example, 250 to 600, preferably 300 to 500, and more preferably 300 to 400. The rosin component of this embodiment may contain, but preferably does not contain, a rosin-amine or ammonium salt obtained by neutralizing rosin or modified rosin with a lower amine or ammonia.

[0035] <Activator> The flux according to this embodiment contains an activator. The activator contains at least an imidazole compound. <Imidazole Compound> In this specification, the term "imidazole compound" refers to a compound having a five-membered heterocyclic ring in which nitrogen atoms are located at the first and third positions of the ring. The melting point of the imidazole compound can be selected arbitrarily, but from the viewpoint of suppressing volatilization, the melting point is preferably 30°C or higher. The melting point is more preferably 40°C or higher, and even more preferably 50°C or higher. The upper limit of the melting point can be selected arbitrarily, but examples include, but are not limited to, 100°C or lower and 90°C or lower.

[0036] The imidazole compound can be selected arbitrarily, but is preferably a compound represented by the following general formula (IZ0): In the formula, hydrogen is bonded to the nitrogen at the 1-position of the five-membered ring.

[0037] [In the formula, R ０１ , R ０２ and R ０３ are each independently a hydrocarbon group having 1 to 5 carbon atoms which may have a substituent, or hydrogen.

[0038] R ０１ , R ０２ and R ０３The hydrocarbon group in R may be a chain hydrocarbon group or a cyclic hydrocarbon group, and a chain hydrocarbon group is preferred. ０１ , R ０２ and R ０３ The chain hydrocarbon group in R is linear or branched. ０１ , R ０２ and R ０３ The chain hydrocarbon group in may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group, and is usually preferably saturated. Examples of the chain saturated aliphatic hydrocarbon group include monovalent chain saturated hydrocarbon groups having 1 to 5 carbon atoms. The number of carbon atoms in the chain saturated aliphatic hydrocarbon group is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 to 2. Examples of the monovalent chain saturated hydrocarbon group having 1 to 5 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, and an n-pentyl group. Among these, a methyl group, an ethyl group, or an n-butyl group is preferred, and a methyl group or an ethyl group is more preferred. R ０１ is preferably an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably an alkyl group having 1 to 2 carbon atoms. ０２ and R ０３ Preferably, one or both of R is hydrogen. ０２ and R ０３ One or both of the groups may be an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 3 carbon atoms, or an alkyl group having 1 to 2 carbon atoms.

[0039] R ０１ , R ０２ and R ０３ When R is a chain hydrocarbon group, some or all of the hydrogen atoms of the chain hydrocarbon group may be substituted with a substituent, for example, a monovalent group containing a hetero atom. Examples of the monovalent group include a halogen atom, a nitro group, an amino group, a hydroxy group, a carboxy group, a nitrile group, and a thiol group. ０１ , R ０２ and R ０３When is a chain hydrocarbon group, a methylene group of the chain hydrocarbon group may be substituted with a divalent group containing a heteroatom. Examples of the divalent group include a carbonyl group, —O—, —C(═O)—O—, —O—C(═O)—, an amide group, and an imino group.

[0040] R ０１ , R ０２ and R ０３ When is a cyclic aliphatic hydrocarbon group, examples thereof include a general cycloalkyl group. Some or all of the hydrogen atoms of the cyclic aliphatic hydrocarbon group may be substituted with a monovalent group. Examples of the monovalent group include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a nitro group, an amino group, a hydroxy group, an aldehyde group, a carboxy group, a nitrile group, and a thiol group.

[0041] R ０１ , R ０２ and R ０３ When is a cyclic aliphatic hydrocarbon group, a carbon atom constituting the ring skeleton may be substituted with a divalent group containing a heteroatom. Examples of the divalent group include a carbonyl group, —O—, —C(═O)—O—, —O—C(═O)—, an amide group, an imino group, or a combination thereof.

[0042] The imidazole compound may be used alone or in combination of two or more. The imidazole compound is preferably one or more selected from the group consisting of 2-propylimidazole, 2-butylimidazole, 2,4-dimethylimidazole, 2-ethylimidazole, and 2-ethyl-4-methylimidazole.

[0043] The content of the imidazole compound in the flux is preferably 0.5% by mass to 30% by mass, more preferably 0.7% by mass to 25% by mass, even more preferably 1.0% by mass to 20% by mass, even more preferably 2.0% by mass to 16% by mass, and particularly preferably 3.0% by mass to 10% by mass, relative to the total mass (100% by mass) of the flux. If necessary, it may be 1.5% by mass to 18% by mass, 2.5% by mass to 15% by mass, or 5.0% by mass to 8.0% by mass.

[0044] The content of the imidazole compound in the solid content of the flux is preferably 5% by mass to 90% by mass, more preferably 20% by mass to 80% by mass, and even more preferably 30% by mass to 70% by mass, relative to the total amount (100% by mass) of the solid content. If necessary, it may be 10% by mass to 85% by mass, 25% by mass to 75% by mass, 35% by mass to 60% by mass, or 40% by mass to 50% by mass.

[0045] The molar ratio of the imidazole compound to the rosin component, expressed as the molar ratio of imidazole compound / rosin component, is 1.3 or more, preferably 1.3 to 30, more preferably 1.5 to 25, even more preferably 1.8 to 20, still more preferably 1.8 to 18, and particularly preferably 1.8 to 15. If necessary, the molar ratio may be 2.0 to 10, 3.0 to 8.0, or 4.0 to 6.0. When the molar ratio is equal to or greater than the lower limit, the rosin component is more easily dissolved in the flux. When the molar ratio is equal to or less than the upper limit, a decrease in insulation resistance can be suppressed, and corrosion of the joint can be reduced.

[0046] The flux according to the present embodiment may contain at least one activator other than the imidazole compound (other activator). When the flux contains an activator other than the imidazole compound, the ratio (mass ratio) of the total content of the imidazole compound and the rosin component to the content of the activator other than the imidazole compound is preferably 2.0 or more, and may be 2.5 or more, 3.0 or more, 5.0 or more, 7.0 or more, 10 or more, 15 or more, 30 or more, 60 or more, or 80 or more.

[0047] [Other Activators] Examples of other activators include organic acids, amines other than imidazole compounds, halogen compounds, organic phosphorus compounds, etc. These will be explained below.

[0048] <Organic Acid> The organic acid can be selected arbitrarily, and examples thereof include carboxylic acids, organic sulfonic acids, etc. Examples of the carboxylic acid include aliphatic carboxylic acids, aromatic carboxylic acids, tricarboxylic acids, hydroxycarboxylic acids, etc. Examples of the aliphatic carboxylic acids include aliphatic monocarboxylic acids, aliphatic dicarboxylic acids, etc.

[0049] Examples of aliphatic monocarboxylic acids include caproic acid, enanthic acid, caprylic acid, pelargonic acid, isopelargonic acid, capric acid, caproleic acid, lauric acid (dodecanoic acid), undecanoic acid, linderic acid, tridecanoic acid, myristoleic acid, pentadecanoic acid, isopalmitic acid, palmitoleic acid, hiragonic acid, hydnocarpic acid, margaric acid, isostearic acid, elaidic acid, petroselinic acid, moroctic acid, eleostearic acid, talic acid, vaccenic acid, riminoleic acid, vernolic acid, sterculic acid, nonadecanoic acid, eicosanoic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, myristic acid, glycolic acid, and thioglycolic acid.

[0050] Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, eicosanedioic acid, citraconic acid, diglycolic acid, tartaric acid, 2,4-diethylglutaric acid, etc. Examples of aromatic carboxylic acids include aromatic monocarboxylic acids such as benzoic acid, 3-hydroxybenzoic acid, 3,4-dihydroxyphenylacetic acid, 2,3-dihydroxybenzoic acid, 3,4,5-trihydroxybenzoic acid, salicylic acid, picolinic acid, p-anisic acid, m-anisic acid, o-anisic acid, parahydroxyphenylacetic acid, and 2-quinolinecarboxylic acid, aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, phenylsuccinic acid, dipicolinic acid, and dibutylaniline diglycolic acid, picolinic acid, dipicolinic acid, and 3-hydroxypicolinic acid, etc.

[0051] Examples of tricarboxylic acids include citric acid and trans aconitic acid.

[0052] Examples of hydroxycarboxylic acids include 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butanoic acid, citric acid, isocitric acid, malic acid, and tartaric acid.

[0053] Examples of the carboxylic acid include tris(2-carboxyethyl) isocyanurate and 1,3-cyclohexanedicarboxylic acid.

[0054] The carboxylic acid may be a polybasic carboxylic acid, such as a dimer acid, a trimer acid, a hydrogenated dimer acid obtained by adding hydrogen to a dimer acid, or a hydrogenated trimer acid obtained by adding hydrogen to a trimer acid.

[0055] Examples of organic sulfonic acids include aliphatic sulfonic acids, aromatic sulfonic acids, etc. Examples of aliphatic sulfonic acids include alkanesulfonic acids, alkanolsulfonic acids, etc.

[0056] The organic acid may be used alone or in combination of two or more. The organic acid is preferably a carboxylic acid, more preferably one or more selected from the group consisting of a dicarboxylic acid, a hydroxycarboxylic acid, and an aromatic carboxylic acid.

[0057] The total content of organic acids in the flux is preferably 0.1% by mass to 5.0% by mass, more preferably 0.13% by mass to 4.0% by mass, even more preferably 0.15% by mass to 3.0% by mass, and even more preferably 0.2% by mass to 2.0% by mass, relative to the total mass (100% by mass) of the flux. If necessary, it may be 0.3% by mass to 2.5% by mass, 0.4% by mass to 1.8% by mass, 0.5% by mass to 1.5% by mass, or 0.7% by mass to 1.0% by mass.

[0058] The total content of organic acids in the solid content of the flux is preferably 0.5% by mass to 30% by mass, more preferably 1.0% by mass to 20% by mass, relative to the total amount (100% by mass) of the solid content, and may be 1.5% by mass to 25% by mass, 2.0% by mass to 20% by mass, 3.0% by mass to 15% by mass, 4.0% by mass to 10% by mass, or 5.0% by mass to 7.0% by mass, as needed.

[0059] <Amines Other Than Imidazole Compounds> The amines other than imidazole compounds can be selected arbitrarily, and examples thereof include azoles other than imidazole compounds, guanidines, amino alcohols, and amine polyoxyalkylene adducts.

[0060] Examples of azoles other than imidazole compounds include 2,4-diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyl-s-triazine, 1,2,4-triazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl ... 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'-te rt-butyl-4'-methyl-2,2'-methylenebisphenol, 1,2,3-benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]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, 5-phenyltetrazole, 3-(N-salicyloyl)amino-1,2,4-triazole, and the like.

[0061] Examples of guanidines include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, 1,3-di-o-cumenylguanidine, and 1,3-di-o-cumenyl-2-propionylguanidine.

[0062] The amino alcohol may, for example, be an alkanolamine such as N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine.

[0063] Examples of the amine polyoxyalkylene adducts include terminal diamine polyalkylene glycols, aliphatic amine polyoxyalkylene adducts, aromatic amine polyoxyalkylene adducts, polyvalent amine polyoxyalkylene adducts, etc. Examples of the alkylene oxide added to the amine polyoxyalkylene adducts include ethylene oxide, propylene oxide, butylene oxide, etc.

[0064] Diamine-terminated polyalkylene glycols are compounds in which both terminals of a polyalkylene glycol are aminated. Examples of diamine-terminated polyalkylene glycols include diamine-terminated polyethylene glycols, diamine-terminated polypropylene glycols, and diamine-terminated polyethylene glycol-polypropylene glycol copolymers. Examples of diamine-terminated polyethylene glycol-polypropylene glycol copolymers include polyethylene glycol-polypropylene glycol copolymer bis(2-aminopropyl) ether and polyethylene glycol-polypropylene glycol copolymer bis(2-aminoethyl) ether.

[0065] The aliphatic amine polyoxyalkylene adduct, aromatic amine polyoxyalkylene adduct, and polyvalent amine polyoxyalkylene adduct are compounds in which a polyoxyalkylene group is bonded to a nitrogen atom of an amine. Examples of the amine include ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, hexamethylenediamine, diethylenetriamine, laurylamine, stearylamine, oleylamine, tallow amine, hardened tallow amine, tallow propyldiamine, metaxylenediamine, tolylenediamine, paraxylenediamine, phenylenediamine, isophoronediamine, 1,10-decanediamine, 1,12-dodecanediamine, 4,4-diaminodicyclohexylmethane, 4,4-diaminodiphenylmethane, butane-1,1,4,4-tetraamine, and pyrimidine-2,4,5,6-tetraamine.

[0066] The amines other than the imidazole compound may be used alone or in combination of two or more. To suppress volatilization, the amines other than the imidazole compound preferably have a melting point of 30°C or higher, preferably 40°C or higher, and more preferably 50°C or higher. The upper limit of the melting point can be selected arbitrarily, but may be, for example, 100°C or lower or 90°C or lower. The total content of amines other than the imidazole compound in the flux is preferably 0% by mass or higher and 10% by mass or lower, more preferably 0% by mass or higher and 5% by mass or lower, relative to the total mass (100% by mass) of the flux. The total content of amines other than the imidazole compound in the solid content of the flux is preferably 0% by mass or higher and 50% by mass or lower, more preferably 0% by mass or higher and 25% by mass or lower, relative to the total amount (100% by mass) of the solid content.

[0067] The flux according to this embodiment may or may not contain an amine other than an imidazole compound having a melting point below 30°C, but preferably does not contain one. When the flux according to this embodiment contains an amine other than an imidazole compound having a melting point below 30°C, the content thereof is preferably more than 0 mass% and not more than 10 mass% relative to the total mass (100 mass%) of the flux. The upper limit of the content may be 8.0 mass%, 6.0 mass%, 4.0 mass%, 2.0 mass%, 1.0 mass%, or 0.5 mass% relative to the total mass (100 mass%) of the flux. The lower limit of the content may be 0 mass%, 0.5 mass%, 1.0 mass%, 1.5 mass%, or 2.0 mass%. The flux according to this embodiment preferably does not contain a lower amine. Examples of the lower amine include methylamine, ethylamine, dimethylamine, diethylamine, and triethylamine.

[0068] <Halogen Compound> Any halogen compound can be selected, and examples thereof include amine hydrohalides and organic halogen compounds other than amine hydrohalides.

[0069] More specifically, examples of amine hydrohalides include cyclohexylamine hydrobromide, hexadecylamine hydrobromide, stearylamine hydrobromide, ethylamine hydrobromide, diphenylguanidine hydrobromide, ethylamine hydrochloride, stearylamine hydrochloride, diethylaniline hydrochloride, diethanolamine hydrochloride, 2-ethylhexylamine hydrobromide, pyridine hydrobromide, isopropylamine hydrobromide, diethylamine hydrobromide, dimethyl ...methylamine hydrobromide, methylamine hydrobromide, methylamine hydrobromide, methyl Benzylamine hydrochloride, rosinamine hydrobromide, 2-ethylhexylamine hydrochloride, isopropylamine hydrochloride, cyclohexylamine hydrochloride, 2-pipecoline hydrobromide, 1,3-diphenylguanidine hydrochloride, dimethylbenzylamine hydrochloride, hydrazine hydrate hydrobromide, dimethylcyclohexylamine hydrochloride, trinonylamine hydrobromide, diethylaniline hydrobromide, 2-diethylaminoethanol hydrobromide, 2-diethylaminoethanol hydrochloride, ammonium chloride, diallylamine hydrochloride, diarylamine hydrochloride Aminomethylamine hydrobromide, diethylamine hydrochloride, triethylamine hydrobromide, triethylamine hydrochloride, hydrazine monohydrochloride, hydrazine dihydrochloride, hydrazine monohydrobromide, hydrazine dihydrobromide, pyridine hydrochloride, aniline hydrobromide, butylamine hydrochloride, hexylamine hydrochloride, n-octylamine hydrochloride, dodecylamine hydrochloride, dimethylcyclohexylamine hydrobromide, ethylenediamine dihydrobromide, rosinamine hydrobromide, 2-phenylimidazole hydrobromide, 4-benzyl Examples of the hydrofluoric acid salt include pyridine hydrobromide, L-glutamic acid hydrochloride, N-methylmorpholine hydrochloride, betaine hydrochloride, 2-pipecoline hydroiodide, cyclohexylamine hydroiodide, 1,3-diphenylguanidine hydrofluoride, diethylamine hydrofluoride, 2-ethylhexylamine hydrofluoride, cyclohexylamine hydrofluoride, ethylamine hydrofluoride, rosinamine hydrofluoride, cyclohexylamine tetrafluoroborate, and dicyclohexylamine tetrafluoroborate.

[0070] Examples of halogen compounds other than amine hydrohalides include amine and tetrafluoroboric acid (HBF ４ ), and salts obtained by reacting amines with boron trifluoride (BF ３ ) can also be used. Examples of the complex include boron trifluoride piperidine.

[0071] Examples of halogen compounds other than amine hydrohalides include halogenated aliphatic compounds. A halogenated aliphatic hydrocarbon group refers to an aliphatic hydrocarbon group in which some or all of the hydrogen atoms constituting the group have been substituted with halogen atoms. Examples of halogenated aliphatic compounds include halogenated aliphatic alcohols and halogenated heterocyclic compounds.

[0072] Examples of halogenated aliphatic alcohols include 1-bromo-2-propanol, 3-bromo-1-propanol, 3-bromo-1,2-propanediol, 1-bromo-2-butanol, 1,3-dibromo-2-propanol, 2,3-dibromo-1-propanol, 1,4-dibromo-2-butanol, and trans-2,3-dibromo-2-butene-1,4-diol.

[0073] Examples of the halogenated heterocyclic compound include compounds represented by the following general formula (h1).

[0074] R ｈ１１ - (R ｈ１２ ) ｎ (h1) [wherein, R ｈ１１ represents an n-valent heterocyclic group. ｈ１２ represents a halogenated aliphatic hydrocarbon group.

[0075] R ｈ１１ In the above, the heterocyclic ring of the n-valent heterocyclic group includes a ring structure in which some of the carbon atoms constituting an aliphatic hydrocarbon or aromatic hydrocarbon ring are substituted with heteroatoms. Examples of heteroatoms in this heterocyclic ring include oxygen atoms, sulfur atoms, and nitrogen atoms. This heterocyclic ring is preferably a 3- to 10-membered ring, and more preferably a 5- to 7-membered ring. Examples of this heterocyclic ring include an isocyanurate ring. Rｈ１２ The halogenated aliphatic hydrocarbon group in R preferably has 1 to 10 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably 3 to 5 carbon atoms. ｈ１２ is preferably a brominated aliphatic hydrocarbon group or a chlorinated aliphatic hydrocarbon group, more preferably a brominated aliphatic hydrocarbon group, and further preferably a brominated saturated aliphatic hydrocarbon group. Examples of halogenated heterocyclic compounds include tris-(2,3-dibromopropyl)isocyanurate.

[0076] Furthermore, examples of halogen compounds other than amine hydrohalides include iodinated carboxyl compounds such as 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, and 5-iodoanthranilic acid; chlorinated carboxyl compounds such as 2-chlorobenzoic acid and 3-chloropropionic acid; and brominated carboxyl compounds such as 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid, and 2-bromobenzoic acid.

[0077] Examples of halogen compounds other than amine hydrohalides include organic chloro compounds, such as chloroalkanes, chlorinated fatty acid esters, chlorendic acid, and chlorendic anhydride.

[0078] The halogen compounds may be used alone or in combination. The halogen compounds are preferably at least one selected from the group consisting of amine hydrohalides, halogenated aliphatic alcohols, and complexes of amines and boron trifluoride. The total content of the halogen compounds in the flux is preferably 0.5% by mass to 15% by mass, more preferably 0.7% by mass to 13% by mass, and even more preferably 1.0% by mass to 10% by mass, based on the total mass (100% by mass) of the flux. If necessary, the content may be 0.5% by mass to 8.0% by mass, 1.5% by mass to 6.0% by mass, 2.0% by mass to 5.0% by mass, or 3.0% by mass to 4.0% by mass.

[0079] The total content of halogen compounds in the solid content of the flux, relative to the total amount (100% by mass) of the solid content, is preferably more than 0% by mass and not more than 70% by mass, more preferably more than 0% by mass and not more than 60% by mass, and even more preferably more than 0% by mass and not more than 45% by mass. If necessary, it may be 0.5% by mass to 30.0% by mass, 1.0% by mass to 20% by mass, 1.5% by mass to 10% by mass, 2.0% by mass to 8.0% by mass, or 3.0% by mass to 5.0% by mass.

[0080] <Organic Phosphorus Compound> The organic phosphorus compound can be selected arbitrarily, and examples thereof include acidic phosphate esters, acidic phosphonate esters, and acidic phosphinate esters. Examples of acidic phosphate esters include methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, monobutyl acid phosphate, butyl acid phosphate, dibutyl acid phosphate, butoxyethyl acid phosphate, 2-ethylhexyl acid phosphate, bis(2-ethylhexyl)phosphate, monoisodecyl acid phosphate, diisodecyl acid phosphate, lauryl acid phosphate, isotridecyl acid phosphate, stearyl acid phosphate, oleyl acid phosphate, beef tallow phosphate, coconut oil phosphate, isostearyl acid phosphate, alkyl acid phosphate, tetracosyl acid phosphate, ethylene glycol acid phosphate, 2-hydroxyethyl methacrylate acid phosphate, and dibutyl pyrophosphate acid phosphate. Examples of acidic phosphonate esters include alkyl phosphonates such as 2-ethylhexyl (2-ethylhexyl) phosphonate, n-octyl (n-octyl) phosphonate, n-decyl (n-decyl) phosphonate, n-butyl (n-butyl) phosphonate, and isodecyl (isodecyl) phosphonate, and diethyl (p-methylbenzyl) phosphonate. Examples of acidic phosphinate esters include phenyl-substituted phosphinic acids. Examples of phenyl-substituted phosphinic acids include phenylphosphinic acid and diphenylphosphinic acid. The organic phosphorus compounds may be used alone or in combination of two or more.

[0081] The total content of the activators other than the imidazole compound in the flux is preferably 0.5% by mass to 15% by mass, more preferably 0.7% by mass to 12% by mass, and even more preferably 1% by mass to 10% by mass, relative to the total mass (100% by mass) of the flux. If necessary, it may be 0.5% by mass to 8.0% by mass, 1.5% by mass to 6.0% by mass, 2.0% by mass to 5.0% by mass, or 3.0% by mass to 4.0% by mass.

[0082] The total content of activators other than the imidazole compound in the solid content of the flux, relative to the total amount (100% by mass) of the solid content, is preferably 0.5% by mass to 80% by mass, more preferably 0.8% by mass to 65% by mass, and even more preferably 1% by mass to 50% by mass. If necessary, it may be 0.5% by mass to 30.0% by mass, 1.0% by mass to 20% by mass, 1.5% by mass to 10% by mass, 2.0% by mass to 8.0% by mass, or 3.0% by mass to 5.0% by mass.

[0083] <Ratio of Imidazole Compound to Rosin Component> In the flux according to this embodiment, the ratio (mass ratio) of the total content of the imidazole compound and the rosin component to the content of the activator other than the imidazole compound may be, for example, 0.5 or more, 1.0 or more, or 1.5 or more, but preferably 2.0 or more. If necessary, it may be 5.0 or more, 10.0 or more, 15 or more, 20 or more, 30 or more, 50 or more, or 80 or more. The upper limit of the ratio (mass ratio) of the total content of the imidazole compound and the rosin component is not particularly limited as long as the effects of the present invention are achieved, but may be 300 or less, 200 or less, or 100 or less. When the mass ratio is equal to or greater than the lower limit, the imidazole compound and the rosin component act to facilitate dissolution of the activator other than the imidazole compound in the flux. When the mass ratio is equal to or less than the upper limit, solderability is likely to be improved.

[0084] <Water> The flux according to this embodiment contains water as a solvent. The water content is 40% by mass or more, based on the total mass (100% by mass) of the flux. If necessary, it may be 50% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, or 90% by mass or more. The upper limit of the water content is not particularly limited as long as the effects of the present invention are achieved, but it may be 98% by mass or less or 96% by mass or less. The water content may be the remainder of the components contained in the flux.

[0085] <Other Components> The flux according to this embodiment may contain other components as needed in addition to the rosin component, activators such as imidazole compounds, and water. Examples of other components include resin components other than the rosin component (other resins), solvents other than water (other solvents), surfactants, thixotropic agents, metal deactivators, antioxidants, silane coupling agents, and colorants. The melting point of the other components is preferably 30°C or higher to suppress volatilization. The melting point may be 50°C or higher, 70°C or higher, 90°C or higher, 100°C or higher, 120°C or higher, or 150°C or higher, as needed. The upper limit can be selected arbitrarily. For example, the melting point may be 200°C or lower, 180°C or lower, or 150°C or lower, but is not limited to these examples. Preferred examples of these components are described below.

[0086] <<Resin Components Other Than Rosin Component (Other Resins)>> The flux according to this embodiment may contain resin components other than the rosin component (other resins), or may not contain other resins, as long as the effects of the present invention are achieved. Examples of other resins include terpene resins, modified terpene resins, terpene phenolic resins, modified terpene phenolic resins, styrene resins, modified styrene resins, xylene resins, modified xylene resins, acrylic resins, polyethylene resins, acrylic-polyethylene copolymer resins, and epoxy resins. Examples of modified terpene resins include aromatic modified terpene resins, hydrogenated terpene resins, and hydrogenated aromatic modified terpene resins. Examples of modified terpene phenolic resins include hydrogenated terpene phenolic resins. Examples of modified styrene resins include styrene-acrylic resins and styrene-maleic acid resins. Examples of modified xylene resins include phenol-modified xylene resins, alkylphenol-modified xylene resins, phenol-modified resol-type xylene resins, polyol-modified xylene resins, and polyoxyethylene-added xylene resins.

[0087] When the flux according to the present embodiment contains other resins, the other resins may be used singly or in combination of two or more.

[0088] When the flux according to the present embodiment contains other resins, the content of the other resins is preferably more than 0 mass % and not more than 10 mass % relative to the total mass (100 mass %) of the flux. The upper limit of the content of the other resins may be 8.0 mass %, 6.0 mass %, 4.0 mass %, 2.0 mass %, 1.0 mass %, or 0.5 mass % relative to the total mass (100 mass %) of the flux. The resin component contained in the flux according to the present embodiment is preferably composed only of a rosin component.

[0089] <<Solvents other than water (other solvents)>> The flux according to the present embodiment may contain a solvent other than water (other solvents) or may not contain other solvents, as long as the effects of the present invention are achieved. The flux according to the present embodiment preferably contains other solvents from the viewpoint of increasing the solubility of solids in the flux.

[0090] The other solvents can be selected arbitrarily, and one type may be used alone, or two or more types may be mixed and used. From the viewpoint of suppressing volatilization, the other solvents preferably have a melting point of 30°C or higher, more preferably 40°C or higher, and even more preferably 50°C or higher. The upper limit of the melting point of the other solvent is not particularly limited, but may be, for example, 200°C, 150°C, 140°C, or 135°C. For example, the melting point may be 35 to 165°C, 45 to 145°C, 55 to 135°C, or 60 to 120°C. Preferred solvents having a melting point of 30° C. or higher include, for example, neopentyl glycol, trimethylolpropane, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyne-2,5-diol, 2-methyl-2-propyl-1,3-propanediol, 2-ethyl-2-methyl-1,3-propanediol, and trimethylolethane.

[0091] When the flux according to the present embodiment contains other solvents having a melting point of 30° C. or higher, from the viewpoint of suppressing the evaporation of the other solvents, the content of the other solvents having a melting point of 30° C. or higher is preferably 70% by mass or higher, more preferably 80% by mass or higher, even more preferably 90% by mass or higher, particularly preferably 95% by mass or higher, and may be 100% by mass, relative to the total amount (100% by mass) of the other solvents.

[0092] The flux according to this embodiment may or may not contain other solvents having a melting point of less than 30° C., but preferably does not contain them. When the flux according to this embodiment contains other solvents having a melting point of less than 30° C., the content of the other solvents having a melting point of less than 30° C. is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, particularly preferably 3% by mass or less, most preferably 2% by mass or less, and may be 1% by mass or less, relative to the total amount (100% by mass) of the other solvents.

[0093] When the flux according to the present embodiment contains other solvents, the content of the other solvents is preferably more than 0% by mass and not more than 40% by mass, more preferably more than 0% by mass and not more than 30% by mass, and even more preferably more than 0% by mass and not more than 20% by mass, relative to the total amount (100% by mass) of the flux. If necessary, the content may be 0.1% by mass to 10% by mass, 1.0% by mass to 7% by mass, or 1.5% by mass to 5% by mass.

[0094] When the flux according to the present embodiment contains other solvents, the content of the other solvents is preferably more than 0% by mass and not more than 80% by mass, more preferably 0.5% by mass to 60% by mass, and even more preferably 1% by mass to 50% by mass, relative to the total amount of solvents (100% by mass). If necessary, the content may be 0.1% by mass to 30% by mass, 1.5% by mass to 20% by mass, 3.0% by mass to 10% by mass, or 4.0% by mass to 6.0% by mass.

[0095] <<Surfactant>> The surfactant can be selected arbitrarily, and examples thereof include nonionic surfactants. Examples of nonionic surfactants include polyoxyalkylene adducts. Examples of alkylene oxides from which polyoxyalkylene adducts are derived include ethylene oxide, propylene oxide, and butylene oxide. Examples of polyoxyalkylene adducts include polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol copolymers, ethylene oxide-resorcinol copolymers, polyoxyalkylene acetylene glycols, polyoxyalkylene glyceryl ethers, polyoxyalkylene alkyl ethers, polyoxyalkylene esters, and polyoxyalkylene alkylamides. Alternatively, examples of nonionic surfactants include polyoxyalkylene adducts of alcohols. Examples of the alcohols include aliphatic alcohols, aromatic alcohols, and polyhydric alcohols. The surfactant is preferably a nonionic surfactant, more preferably a polyoxyalkylene adduct, still more preferably one or more selected from the group consisting of polyethylene glycol, polypropylene glycol, and polyethylene glycol-polypropylene glycol copolymer, with polyethylene glycol being particularly preferred. When a polyoxyalkylene adduct is used as the surfactant, the weight-average molecular weight of the polyoxyalkylene adduct is preferably 100 to 4,000, more preferably 150 to 2,000, and even more preferably 150 to 1,200.

[0096] The surfactant may be used alone or in combination of two or more. The content of the surfactant in the flux is, for example, 0.001% by mass to 10% by mass, preferably 0.01% by mass to 10% by mass, relative to the total mass (100% by mass) of the flux. If necessary, the content may be 0.003% by mass to 6% by mass, 0.005% by mass to 4% by mass, or 0.008% by mass to 2.0% by mass.

[0097] The total content of surfactants in the solid content of the flux is preferably more than 0% by mass and not more than 40% by mass, more preferably more than 0% by mass and not more than 30% by mass, and even more preferably 1.0% by mass to 30% by mass, relative to the total amount (100% by mass) of the solid content. If necessary, it may be 0.5% by mass to 25% by mass, 3.0% by mass to 20% by mass, or 5.0% by mass to 10% by mass.

[0098] <Thixotropic Agent> The thixotropic agent can be selected arbitrarily, and examples thereof include ester-based thixotropic agents, amide-based thixotropic agents, and sorbitol-based thixotropic agents.

[0099] Examples of ester-based thixotropic agents include ester compounds, and specific examples include hydrogenated castor oil and ethyl myristate.

[0100] Examples of amide-based thixotropic agents include monoamides, bisamides, and polyamides. Examples of monoamides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, saturated fatty acid amide, oleic acid amide, erucic acid amide, unsaturated fatty acid amide, 4-methylbenzamide (p-toluamide), p-toluenemethane amide, aromatic amide, hexamethylenehydroxystearic acid amide, substituted amide, methylolstearic acid amide, methylol amide, and fatty acid ester amide. Examples of bisamides include ethylenebisfatty acid (fatty acid carbon number: C6 to 24) amide, ethylenebishydroxyfatty acid (fatty acid carbon number: C6 to 24) amide, hexamethylenebisfatty acid (fatty acid carbon number: C6 to 24) amide, hexamethylenebishydroxyfatty acid (fatty acid carbon number: C6 to 24) amide, and aromatic bisamides. Examples of fatty acids that are raw materials for the bisamides include stearic acid (carbon number: C18), oleic acid (carbon number: C18), lauric acid (carbon number: C12), etc. Examples of polyamides include saturated fatty acid polyamides, unsaturated fatty acid polyamides, aromatic polyamides, 1,2,3-propanetricarboxylic acid tris(2-methylcyclohexylamide), cyclic amide oligomers, and acyclic amide oligomers.

[0101] Examples of the cyclic amide oligomer include an amide oligomer obtained by cyclic polycondensation of a dicarboxylic acid and a diamine, an amide oligomer obtained by cyclic polycondensation of a tricarboxylic acid and a diamine, an amide oligomer obtained by cyclic polycondensation of a dicarboxylic acid and a triamine, an amide oligomer obtained by cyclic polycondensation of a tricarboxylic acid and a triamine, an amide oligomer obtained by cyclic polycondensation of a dicarboxylic acid, a tricarboxylic acid, and a diamine, an amide oligomer obtained by cyclic polycondensation of a dicarboxylic acid, a tricarboxylic acid, and a triamine, an amide oligomer obtained by cyclic polycondensation of a dicarboxylic acid, a diamine, and a triamine, an amide oligomer obtained by cyclic polycondensation of a tricarboxylic acid, a diamine, and a triamine, and an amide oligomer obtained by cyclic polycondensation of a dicarboxylic acid, a tricarboxylic acid, a diamine, and a triamine.

[0102] The acyclic amide oligomer may be an amide oligomer obtained by acyclic polycondensation of a monocarboxylic acid with a diamine and / or triamine, or an amide oligomer obtained by acyclic polycondensation of a dicarboxylic acid and / or tricarboxylic acid with a monoamine. In the case of an amide oligomer containing a monocarboxylic acid or a monoamine, the monocarboxylic acid or monoamine functions as a terminal molecule, resulting in an acyclic amide oligomer with a reduced molecular weight. Furthermore, when the acyclic amide oligomer is an amide compound obtained by acyclic polycondensation of a dicarboxylic acid and / or tricarboxylic acid with a diamine and / or triamine, it becomes an acyclic high-molecular-weight amide polymer. Furthermore, the acyclic amide oligomer also includes an amide oligomer obtained by acyclic condensation of a monocarboxylic acid with a monoamine.

[0103] Examples of sorbitol-based thixotropic agents include dibenzylidene-D-sorbitol, bis(4-methylbenzylidene)-D-sorbitol, (D-)sorbitol, monobenzylidene (-D-)sorbitol, and mono(4-methylbenzylidene)-(D-)sorbitol.

[0104] The flux according to this embodiment may contain no thixotropic agent or may contain a thixotropic agent. When the flux according to this embodiment contains a thixotropic agent, the thixotropic agent may be used alone or in combination of two or more types. The content of the thixotropic agent in the flux and the content of the thixotropic agent in the solid content of the flux can be selected arbitrarily as needed.

[0105] <<Metal Deactivator>> Examples of metal deactivators include hindered phenol compounds, nitrogen compounds, etc. The term "metal deactivator" used herein refers to a compound that has the ability to prevent metals from deteriorating due to contact with certain compounds.

[0106] The hindered phenol compound refers to a phenol compound having a bulky substituent (for example, a branched or cyclic alkyl group such as a t-butyl group) at least on one of the ortho positions of the phenol. The hindered phenol compound is not particularly limited, and examples thereof include bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylenebis(oxyethylene)], N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2'-dihydroxy-3,3'-bis(2-methyl-2-propanol), ... bis(α-methylcyclohexyl)-5,5'-dimethyldiphenylmethane, 2,2'-methylenebis(6-tert-butyl-p-cresol), 2,2'-methylenebis(6-tert-butyl-4-ethylphenol), triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,4-bis(α-methylcyclohexyl)-5,5'-dimethyldiphenylmethane, 2,2'-methylenebis(6-tert-butyl-p-cresol), 2,2'-methylenebis(6-tert-butyl-4-ethylphenol), triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis ... N,N'-Hexamethyl bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), N-octylthio-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, pentaerythrityl tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2-thio-diethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-Hexamethyl Examples of such compounds include benzenebis(3,5-di-tert-butyl-4-hydroxy-hydrocinnamamide), 3,5-di-tert-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxamide, and compounds represented by the following chemical formula:

[0107] (wherein Z is an optionally substituted alkylene group. R ８１ and R ８２ R is each independently an optionally substituted alkyl group, aralkyl group, aryl group, heteroaryl group, cycloalkyl group, or heterocycloalkyl group. ８３ and R ８４ are each independently an optionally substituted alkyl group.

[0108] Examples of the nitrogen compound in the metal deactivator include hydrazide-based nitrogen compounds, amide-based nitrogen compounds, triazole-based nitrogen compounds, and melamine-based nitrogen compounds.

[0109] The hydrazide nitrogen compound may be any nitrogen compound having a hydrazide skeleton, and examples thereof include dodecanedioic acid bis[N2-(2-hydroxybenzoyl)hydrazide], N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, decanedicarboxylic acid disalicyloylhydrazide, N-salicylidene-N'-salicylhydrazide, m-nitrobenzhydrazide, 3-aminophthalhydrazide, phthalic acid dihydrazide, adipic acid hydrazide, oxalobis(2-hydroxy-5-octylbenzylidenehydrazide), N'-benzoylpyrrolidonecarboxylic acid hydrazide, and N,N'-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hydrazine.

[0110] The amide nitrogen compound may be any nitrogen compound having an amide skeleton, and examples thereof include N,N'-bis{2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxyl]ethyl}oxamide.

[0111] The triazole-based nitrogen compound may be any nitrogen compound having a triazole skeleton, and examples thereof include N-(2H-1,2,4-triazol-5-yl)salicylamide, 3-amino-1,2,4-triazole, and 3-(N-salicyloyl)amino-1,2,4-triazole.

[0112] The melamine-based nitrogen compound may be any nitrogen compound having a melamine skeleton, such as melamine and melamine derivatives. More specifically, examples include trisaminotriazine, alkylated trisaminotriazine, alkoxyalkylated trisaminotriazine, melamine, alkylated melamine, alkoxyalkylated melamine, N2-butylmelamine, N2,N2-diethylmelamine, and N,N,N',N',N'',N''-hexakis(methoxymethyl)melamine. One type of metal deactivator may be used alone, or two or more types may be mixed and used. The content of the metal deactivator in the flux and the content of the metal deactivator in the solid content of the flux can be selected as needed.

[0113] <Antioxidant> The antioxidant can be selected arbitrarily, and examples thereof include hindered phenol-based antioxidants such as 2,2'-dihydroxy-3,3'-bis(α-methylcyclohexyl)-5,5'-dimethyldiphenylmethane. One antioxidant may be used alone, or two or more antioxidants may be mixed and used. The content of the antioxidant in the flux and the content of the antioxidant in the solid content of the flux can be selected arbitrarily as needed. <Silane Coupling Agent> The silane coupling agent can be selected arbitrarily as needed. <Colorant, etc.> The colorant can be selected arbitrarily as needed.

[0114] [Solubility and Odor Characteristics] The flux according to the present embodiment described above contains an imidazole compound and contains 40% or more by mass of water relative to the total mass (100% by mass) of the flux. The flux according to the present embodiment is suitable for flow soldering. Furthermore, this flux has sufficient solubility for hydrophobic components such as rosin and a reduced odor. While the reason for this effect is unclear, it is speculated as follows: It is speculated that the imidazole compound contained in the flux increases the solubility of the rosin component, which has low solubility in water. Furthermore, the flux uses an imidazole compound instead of a highly volatile lower amine, as described in Patent Document 1. This is speculated to reduce odor and improve the working environment.

[0115] (Method for manufacturing a bonded body) A method for manufacturing a bonded body according to the second aspect includes a step of soldering a solder alloy to the surface of a substrate treated with the flux according to the first aspect to obtain a bonded body. Note that the bonded body may refer to a substrate treated with flux and a member different from the substrate, which are joined by soldering using a solder alloy. The solder alloy may be selected arbitrarily as needed. An example of one embodiment of the method for manufacturing a bonded body according to the second aspect will be described below. The method for manufacturing a bonded body according to this embodiment is a method including, in this order, a component mounting step, a flux application step, a preheating step, and a soldering step.

[0116] [Component Mounting Step] In the component mounting step, components are mounted on a substrate. The mounting method may be a method generally known in the art. The substrate may be selected arbitrarily, for example, a printed wiring board. The components may also be selected arbitrarily, for example, an integrated circuit, a transistor, a diode, a resistor, a capacitor, etc.

[0117] [Flux Application Step] In the flux application step, the flux of the above embodiment is applied to the soldering surface of the board on which the components are mounted. The soldering surface is the surface on which soldering is performed. The flux application device, application method, and application conditions can be selected as needed, and examples include the use of a spray fluxer and a foaming fluxer. Among these, a spray fluxer is preferred from the viewpoint of the stability of the amount of application. The amount of flux to be applied can be selected as needed, and is preferably 30 to 180 mL / m from the viewpoint of solderability. ２ is preferably 40 to 150 mL / m ２ More preferably, it is 50 to 120 mL / m ２ It is particularly preferred that:

[0118] [Preheating Step] In the preheating step, the substrate carrying components with flux applied to the soldering surface is preheated. The temperature to which the substrate is heated in the preheating step can be selected as desired, but is preferably 80 to 130°C, and more preferably 90 to 120°C.

[0119] [Soldering Process] In the soldering process, the soldering surface of the substrate carrying the components after the preheating process is brought into contact with molten solder prepared by melting a solder alloy. The method for bringing the molten solder into contact with the surface to be soldered is not particularly limited as long as it is a method that allows the molten solder to come into contact with the substrate. Examples of such methods include the jet method and the immersion method. The equipment and conditions used for soldering can be selected arbitrarily. The jet method is a method in which the soldering surface of the substrate carrying the components is brought into contact with a jet of molten solder. The immersion method is a method in which the soldering surface of the substrate carrying the components is brought into contact with the liquid surface of stationary molten solder.

[0120] The solder alloy can be selected arbitrarily, and solder alloys of known compositions can be used. Examples of solder alloys include solder alloys of simple Sn, Sn-based solder alloys, and Sn-Bi-based solder alloys. Sn-based solder alloys are solder alloys produced by adding one or more elements selected from the group consisting of Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, Pb, and P to Sn. Elements other than Sn contained in the Sn-based solder alloy can be selected arbitrarily.

[0121] For example, the solder alloy may be a solder containing only Sn, or a solder alloy such as Sn—Ag, Sn—Cu, Sn—Ag—Cu, Sn—Bi, or Sn—In, or an alloy of these to which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, or P has been added. Alternatively, the solder alloy may be a Sn—Pb solder alloy or a Sn—Pb solder alloy to which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, or P has been added. Preferably, the solder alloy does not contain Pb.

[0122] The soldering conditions in the soldering step may be appropriately set depending on the melting point of the solder. For example, when a Sn—Ag—Cu solder alloy is used, the molten solder temperature is preferably 230 to 280° C., and more preferably 250 to 270° C. Alternatively, when a Sn—Bi solder alloy (a solder alloy containing Sn and Bi) is used, the molten solder temperature is preferably 170 to 220° C., and more preferably 180 to 200° C.

[0123] The method for manufacturing a bonded body according to the present embodiment described above uses the flux according to the embodiment, and therefore, it is possible to reduce odors and improve the working environment.

[0124] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0125] <Preparation of Flux> (Examples 1 to 40, Comparative Examples 1 to 10) Each flux in the examples and comparative examples was prepared by mixing materials according to the compositions shown in Tables 1 to 5 below. The components of the raw materials used are shown below. The contents in Tables 1 to 5 are in mass % when the total mass of the flux is 100 mass %, and blank spaces indicate 0 mass %.

[0126] Rosin components: Acrylic acid modified hydrogenated rosin (acid value: 235 mg KOH / g, molecular weight: 367) Acrylic acid modified rosin (acid value: 240 mg KOH / g, molecular weight: 365) Maleic acid modified rosin (acid value: 325 mg KOH / g, molecular weight: 368) Phenol modified rosin (acid value: 150 mg KOH / g, molecular weight: 500)

[0127] Other resins: Terpene phenol resin (molecular weight 600)

[0128] Imidazole compounds: 2-ethylimidazole (molecular weight 96.13) 2-ethyl-4-methylimidazole (molecular weight 110.16)

[0129] Other activators: The following amines, organic acids, and halogen compounds other than the imidazole compounds were used: Amines other than imidazole compounds: Triethylamine N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine Polypropylene glycol-BLOCK-polyethylene glycol-BLOCK-polypropylene glycol bis(2-aminopropyl ether) 1,2,3-benzotriazole, pyrazole, 1,2,4-triazole

[0130] Organic acids: Picolinic acid, Adipic acid, Succinic acid, Malic acid Halogen compounds: Ethylamine HBr salt, trans-2,3-dibromo-2-butene-1,4-diol, Boron trifluoride piperidine

[0131] Surfactant: Polyoxyethylene nonylphenyl ether

[0132] Ion-exchanged water and other solvents were used as solvents. Water: Ion-exchanged water Other solvents: Neopentyl glycol (melting point 129°C), trimethylolpropane (melting point 58°C), 2,5-dimethyl-2,5-hexanediol (melting point 88°C)

[0133] [Evaluation of Material Properties] [Acid Value Measurement] The acid value of the rosin components was measured in accordance with 3.1 Neutralization Titration Method of JIS K0070 "Test Methods for Acid Value, Saponification Value, Ester Value, Iodine Value, Hydroxyl Value, and Unsaponifiable Matter of Chemical Products." 3 g of each rosin component was dissolved in ethanol / diethyl ether (mixing ratio 1:1). Using phenolphthalein as an indicator, titration was performed with a 0.1 mol / L KOH ethanol solution. The endpoint was when the solution turned slightly red.

[0134] [Molecular Weight Measurement] The weight average molecular weights (polystyrene equivalent) of the rosin component and other resins were measured using the following equipment under the following conditions: Analytical equipment: EcoSEC HLC-8320GPC manufactured by Tosoh Corporation Mobile phase: THF Column: TSKguard column HXL (guard column) manufactured by Tosoh + TSKgel G2000HXL manufactured by Tosoh + TSKgel G1000HXL manufactured by Tosoh Column temperature: 40°C Flow rate: 1.0 (mL / min) Detector: RI+UV, Pol(+), Res(0.5 s), UV wavelength 254 nm Injection volume: 50 μL Standard substance: "PStQuick F, standard polystyrene kit for GPC" manufactured by Tosoh was used. The analytical results are in polystyrene equivalent.

[0135] The evaluation of solubility and odor were carried out according to the evaluation methods described in the following section, and the results are shown in Tables 1 to 5.

[0136] <Evaluation of Flux> <Evaluation of Solubility> (1) Evaluation Method After mixing the raw materials to prepare a flux, the solubility of the raw materials in the flux was evaluated visually.

[0137] (2) Evaluation criteria 1: The material was completely dissolved and transparent. 2: The material was dissolved immediately after mixing, but precipitate was observed after 1 hour. 3: The material was slightly cloudy immediately after mixing and remained cloudy even after 1 hour. 4: The material became cloudy immediately after mixing and remained cloudy after 1 hour, but the solvent and solids did not separate. 5: The solvent and solids were almost completely separated. Ratings 1 to 4 were considered pass, and rating 5 was considered fail.

[0138] <Odor Evaluation> (1) Evaluation Method After mixing the raw materials to prepare a flux, the odor of the flux was evaluated by sensory evaluation. The evaluation was carried out at room temperature (25°C). The odor evaluation was carried out by one person who is capable of odor evaluation.

[0139] (2) Evaluation Criteria 1: No odor was observed. 2: An irritating odor was observed. Evaluation 1 was considered to be acceptable, and evaluation 2 was considered to be unacceptable.

[0140]

[0141] As shown in Table 1, Examples 1 and 2, which contained an imidazole compound, were rated better in solubility than Comparative Examples 1 to 5, which did not contain an imidazole compound. Comparative Example 1, which contained triethylamine (melting point -115°C), was rated 1 in solubility, but 2 in odor.

[0142]

[0143] As shown in Table 2, Examples 3 to 16, in which the molar ratio of imidazole compound to rosin component was 1.3 or more, had a better evaluation of solubility than Comparative Example 9, in which the molar ratio of imidazole compound to rosin component was less than 1.3. Examples 3 to 9 and Examples 11 to 13, in which the molar ratio of imidazole compound to rosin component was 1.8 or more and 20 or less, had a better evaluation of solubility than Examples 10 and Examples 14 to 16, in which the molar ratio was outside the above range.

[0144] As shown in Table 3, Examples 1 and 17 to 19, which contained a rosin component, were evaluated as having better solubility than Comparative Example 10, which did not contain a rosin component but contained a terpene phenol resin.

[0145]

[0146] As shown in Table 4, Example 6, in which the ratio of the total content of the imidazole compound and the rosin component to the content of the other activators was 2 or more, had a better solubility rating than Examples 20 and 21, in which the ratio was less than 2. Similarly, Examples 22 to 31, in which the ratio was 2 or more, were each evaluated as 1 for solubility.

[0147]

[0148] Example 32, which contained a solvent other than water with a melting point of 30°C or higher, had a better solubility rating than Example 13, which contained no solvent other than water. Examples 32 and 35 to 40, in which the imidazole compound content was 3% by mass or more relative to the total mass of the flux (100% by mass), had a better solubility rating than Examples 33 and 34, in which the imidazole compound content was 1% by mass. As proven by the above experiments, it is a surprising effect that rosin has excellent solubility even when it contains a large amount of water.

[0149] According to the present invention, it is possible to provide a flux that sufficiently dissolves hydrophobic components such as rosin even when water is used as the main solvent and has a reduced odor, and a method for manufacturing a bonded body using the flux. The flux of the present invention is suitable for use in flow soldering.

Claims

1. A flux comprising a rosin component, an activator, and water, the activator including an imidazole compound, the water content being 40 mass% or more relative to the total mass (100 mass%) of the flux, and a molar ratio of the imidazole compound to the rosin component, expressed as a molar ratio of imidazole compound / rosin component, being 1.3 or more.

2. The flux according to claim 1, wherein the rosin component includes at least one of an acid-modified rosin and an acid-modified hydrogenated rosin.

3. The flux according to claim 1, wherein the molar ratio of the imidazole compound to the rosin component is 1.8 or more and 20 or less, expressed as a molar ratio of the imidazole compound / the rosin component.

4. The flux according to claim 3, further comprising an activator other than the imidazole compound, wherein the ratio (mass ratio) of the total content of the imidazole compound and the rosin component to the content of the activator other than the imidazole compound is 2 or more.

5. The flux according to claim 1, further comprising a solvent having a melting point of 30°C or higher.

6. The flux according to claim 5, wherein the rosin component includes at least one of an acid-modified rosin and an acid-modified hydrogenated rosin.

7. The flux according to claim 4, wherein the activator other than an imidazole compound is at least one selected from the group consisting of an organic acid, an amine other than an imidazole compound, and a halogen compound.

8. The flux according to claim 1, wherein the imidazole compound is a compound represented by the following formula: [In the formula, R ０１ , R ０２ and R ０３ are each independently a hydrocarbon group having 1 to 5 carbon atoms which may have a substituent, or hydrogen.

9. A method for producing a joint, comprising the steps of treating a surface of a substrate with the flux according to any one of claims 1 to 8, and soldering a solder alloy to the treated surface of the substrate to obtain a joint.

10. The method for producing a bonded body according to claim 9, further comprising a step of attaching a component to the substrate before treating the surface of the substrate with the flux, and the bonded body is a bond between the component and the substrate.