Flux for water washing and solder paste for water washing

Abstract

To provide a flux with excellent water washability for flux residue, which can suppress the occurrence of head-in-pillow defects called HiP in the assembly of BGA (Ball Grid Array) and CSP (Chip Size Package), and a solder paste containing the flux. [Solution] A water-washing flux is used that contains a water-soluble base agent selected from nonionic surfactants, an organic acid, and a solvent, wherein the organic acid includes dimer acid and organic sulfonic acid.

Description

Technical Field

[0001] The present invention relates to a water-washable flux and a water-washable solder paste.

Background Art

[0002] Fixing components to a substrate and electrically connecting components to a substrate are generally performed by soldering. In soldering, a flux, a solder powder, and a solder paste obtained by mixing a flux and a solder powder are used. In soldering using a solder paste, first, after the solder paste is printed on a substrate, components are mounted, and the substrate with the mounted components is heated in a heating furnace called a reflow furnace. Thereby, the solder powder contained in the solder paste is melted, and the components are soldered to the substrate.

[0003] A flux has the effect of chemically removing metal oxides present on the metal surface of a bonding object to be soldered and on the solder, and enabling movement of metal elements at the boundary between the two. Therefore, by performing soldering using a flux, an intermetallic compound is formed between the two, and a strong bond can be obtained.

[0004] Generally, a flux contains a resin component, a solvent, an activator, a thixotropic agent, and the like. In order to improve the reliability of bonding between the solder and the bonding object, excess flux after soldering (flux residue) may be removed by cleaning. Flux that remains even after cleaning is called cleaning residue. Cleaning residue may cause a decrease in insulation property due to ion migration or corrosion of the substrate. Alternatively, it may impair the adhesion of materials when performing wire bonding, underfill insertion, moisture-proof coating, or the like in a subsequent process.

[0005] Traditionally, rosin, which has excellent electrical insulation and moisture resistance, has been used as the resin component in flux. However, fluxes containing rosin require organic solvents as cleaning solutions after soldering, which can sometimes cause problems in terms of safety and the environment. Therefore, there is a need for a water-cleanable flux that can be easily washed off with water after soldering. In contrast, Patent Document 1 describes a flux containing an organic sulfonic acid-based surfactant and a nonionic surfactant with a specific mass-average molecular weight. According to the flux described in Patent Document 1, the cleanability with water after soldering is improved. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-086400 [Overview of the project] [Problems that the invention aims to solve]

[0007] In recent years, with the increasing density of mounting, the gaps beneath chip components have become increasingly narrow. These narrow gaps are difficult for cleaning solutions to reach, posing a problem for flux cleaning. Surface mount components such as BGA (Ball Grid Array) and CSP (Chip Size Package) are used for high-density mounting. These have a structure in which solder balls are arranged in a grid as electrodes. In BGA mounting of CSPs, a pillow defect called HiP (Head in Pillow) is a problem due to factors such as low flux activity and package warping during mounting. In contrast, the solder paste using flux described in Patent Document 1 has sufficient water washability of flux residue, but it is difficult to suppress the occurrence of HiP.

[0008] Therefore, the present invention aims to provide a flux that has excellent water washability and can suppress the generation of HiP, and a solder paste containing the same. [Means for solving the problem]

[0009] To solve the above problems, the present invention employs the following configuration. [1] A water-washing flux comprising a water-soluble base agent selected from nonionic surfactants, an organic acid, and a solvent, wherein the organic acid includes dimer acid and organic sulfonic acid.

[0010] [2] The water washing flux according to [1], wherein the content of the dimer acid is 1 to 30% by mass with respect to the total mass of the water washing flux, and the content of the organic sulfonic acid is 0.1 to 5% by mass with respect to the total mass of the water washing flux.

[0011] [3] The water washing flux according to [1] or [2], wherein the mass ratio of the dimer acid to the organic sulfonic acid is greater than 1.0 and less than or equal to 20.

[0012] [4] The water washing flux according to any one of [1] to [3], wherein the organic acid further comprises a dibasic acid having 4 or fewer carbon atoms.

[0013] [5] The water washing flux according to [4], wherein the content of the dibasic acid having 4 or fewer carbon atoms is greater than 0% by mass and less than or equal to 5% by mass with respect to the total mass of the water washing flux.

[0014] [6] The water washing flux according to any one of [1] to [5], wherein the boiling point of the solvent is 260°C or higher.

[0015] [7] A solder paste for water washing containing a water washing flux described in any one of items [1] to [6] and solder alloy powder. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a flux that is excellent in water washability and can suppress the occurrence of HiP, and a solder paste containing the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] [Figure 1] It is a figure showing a reflow profile in the evaluation of the example. MODES FOR CARRYING OUT THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail.

[0019] In the present specification, when a numerical range is described as, for example, "1 to 10 parts by mass", it means a range from 1 part by mass to 10 parts by mass, and means a numerical range including the lower limit of 1 part by mass and the upper limit of 10 parts by mass.

[0020] (Flux for water washing) The flux for water washing according to the present embodiment contains a water-soluble base agent selected from nonionic surfactants, an organic acid, and a solvent. In the present specification, the flux for water washing means a flux whose flux residue can be removed by washing with water. In order to remove flux residue by water washing, the flux for water washing according to the present embodiment contains a water-soluble base agent which is a component having high affinity with water, and a solvent. Hereinafter, the flux for water washing may be simply referred to as flux.

[0021] <Water-soluble base agent> The water-soluble base agent is a component exhibiting affinity with water. A component exhibiting affinity with water is a component having a chemical species that exhibits affinity with water. A chemical species that forms hydrogen bonds with water is a chemical species that forms hydrogen bonds with water. Examples of the chemical species that form hydrogen bonds with water include atoms such as oxygen atoms and nitrogen atoms, or functional groups containing these atoms. Examples of functional groups that exhibit affinity for water include hydroxyl groups, carboxyl groups, amino groups, carbonyl groups, ether bonds, ester bonds, amide bonds, -N=, and cyano groups.

[0022] The water-washing flux according to this embodiment contains a water-soluble base agent selected from nonionic surfactants. Examples of nonionic surfactants include polyoxyalkylene adducts. Examples of alkylene oxides derived from polyoxyalkylene adducts include ethylene oxide (EO) and propylene oxide (PO). Examples of polyoxyalkylene adducts include polyalkylene glycols, polyoxyalkylene adducts of alcohols, polyoxyalkylene adducts of carboxylic acids, and polyoxyalkylene adducts of carboxylic acid amides.

[0023] Examples of polyalkylene glycols include polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol copolymers, and polyoxyalkylene acetylene glycols.

[0024] Examples of alcohols used in polyoxyalkylene adducts of alcohols include aliphatic alcohols and aromatic alcohols. Examples of the aforementioned aliphatic alcohols include lauryl alcohol, myristyl alcohol, cetanol, 1-heptadecanol, stearyl alcohol, oleyl alcohol, nonadecyl alcohol, arachidyl alcohol, heneicosanol, behenyl alcohol, and glycerin. Examples of the aforementioned aromatic alcohols include phenol, benzyl alcohol, p-cumylphenol, naphthol, octylphenol, nonylphenol, dodecylphenol, and resorcinol.

[0025] Examples of polyoxyalkylene adducts of carboxylic acids include polyoxyalkylene esters.

[0026] Examples of polyoxyalkylene adducts of carboxylic acid amides include polyoxyalkylene alkylamides.

[0027] The water-soluble base agent contained in the water-washing flux according to this embodiment may be a single nonionic surfactant or a mixture of two or more. Among the above, it is preferable to use at least one selected from the group consisting of polyoxyalkylene adducts of alcohols and polyalkylene glycols as the water-soluble base agent, and more preferably to use at least one selected from the group consisting of polyoxyalkylene adducts of aliphatic alcohols, polyoxyalkylene adducts of aromatic alcohols and polyalkylene glycols. From the viewpoint of improving water washability, it is even more preferable to use at least one water-soluble base agent selected from the group consisting of polyoxyalkylene adducts of aliphatic alcohols and polyoxyalkylene adducts of aromatic alcohols, and it is even more preferable to use a combination of a polyoxyalkylene adduct of aliphatic alcohol and a polyoxyalkylene adduct of aromatic alcohol.

[0028] Among polyalkylene glycols, polyethylene glycol is preferred as the water-soluble base agent.

[0029] As the water-soluble base agent, among polyoxyalkylene adducts of aliphatic alcohols, it is preferable to use an ethylene oxide (EO) adduct of an aliphatic alcohol, more preferably an ethylene oxide (EO) adduct of at least one aliphatic alcohol selected from the group consisting of cetanol, stearyl alcohol, oleyl alcohol, heneicosanol, and behenyl alcohol, and even more preferably an ethylene oxide (EO) adduct of behenyl alcohol. As the water-soluble base agent, among polyoxyalkylene adducts of aromatic alcohols, it is preferable to use an ethylene oxide (EO) adduct of an aromatic alcohol, more preferably at least one selected from the group consisting of an ethylene oxide (EO) adduct of phenol, an ethylene oxide (EO) adduct of octylphenol, and an ethylene oxide (EO) adduct of resorcinol, and even more preferably an ethylene oxide (EO) adduct of resorcinol.

[0030] The content of the polyalkylene glycol is preferably 0 to 45% by mass, more preferably 0 to 40% by mass, even more preferably 0 to 35% by mass, and particularly preferably 0 to 30% by mass, relative to the total mass of the water-soluble base agent. The upper and lower limits of the above range can be combined in any way.

[0031] The content of the polyoxyalkylene adduct of the alcohol is preferably 55 to 100% by mass, more preferably 60 to 100% by mass, even more preferably 65 to 100% by mass, and particularly preferably 70 to 100% by mass, relative to the total mass of the water-soluble base agent. The upper and lower limits of the above range can be any combination.

[0032] The content of the aliphatic alcohol polyoxyalkylene adduct is preferably 10 to 100% by mass, more preferably 20 to 75% by mass, and even more preferably 30 to 60% by mass, relative to the total mass of the water-soluble base agent. The upper and lower limits within the above range can be any combination. When the content of the aliphatic alcohol polyoxyalkylene adduct is within the preferred range, the printability is improved in addition to the water washability.

[0033] The content of the polyoxyalkylene adduct of the aromatic alcohol is preferably 0 to 90% by mass, more preferably 25 to 80% by mass, and even more preferably 40 to 70% by mass, relative to the total mass of the water-soluble base agent. The upper and lower limits within the above range can be combined arbitrarily. When the content of the aromatic alcohol polyoxyalkylene adduct is within the preferred range, the printability is improved in addition to the water washability.

[0034] When the water-soluble base agent contains both a polyoxyalkylene adduct of an aliphatic alcohol and a polyoxyalkylene adduct of an aromatic alcohol, the ratio of the content of the polyoxyalkylene adduct of an aliphatic alcohol to the polyoxyalkylene adduct of an aromatic alcohol is preferably 1 / 9 to 6 / 4, more preferably 2 / 8 to 5 / 5, and even more preferably 3 / 7 to 4 / 6. The upper and lower limits within the above range can be combined arbitrarily.

[0035] The content of the water-soluble base agent is preferably 5 to 75% by mass, more preferably 10 to 65% by mass, even more preferably 15 to 55% by mass, and particularly preferably 15 to 45% by mass, relative to the total mass of the flux. The upper and lower limits within the above range can be combined arbitrarily. When the content of the water-soluble base agent is above the lower limit of the preferred range, the water washability is good.

[0036] The polyalkylene glycol content is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, even more preferably 0 to 15% by mass, and particularly preferably 0 to 10% by mass, relative to the total mass of the flux. The upper and lower limits within the above range can be combined in any way.

[0037] The content of the polyoxyalkylene adduct of the alcohol is preferably 10 to 60% by mass, more preferably 15 to 55% by mass, even more preferably 15 to 50% by mass, and particularly preferably 20 to 45% by mass, relative to the total mass of the flux. The upper and lower limits of the above range can be combined arbitrarily.

[0038] The content of the aliphatic alcohol polyoxyalkylene adduct is preferably 5 to 40% by mass, more preferably 7 to 30% by mass, and even more preferably 9 to 25% by mass, relative to the total mass of the flux. The upper and lower limits of the above range can be combined in any way. When the content of the aliphatic alcohol polyoxyalkylene adduct is within the preferred range, the printability is improved in addition to the water washability.

[0039] The content of the polyoxyalkylene adduct of the aromatic alcohol is preferably 0 to 40% by mass, more preferably 7 to 30% by mass, and even more preferably 9 to 25% by mass, relative to the total mass of the flux. The upper and lower limits of the above range can be combined arbitrarily. When the content of the aromatic alcohol polyoxyalkylene adduct is within the preferred range, the printability is improved in addition to the water washability.

[0040] <Organic acid> The water-washing flux according to this embodiment contains dimer acid and organic sulfonic acid as organic acids.

[0041] Dimer acid The water-washing flux according to this embodiment contains dimer acid as an organic acid. Dimer acids are dibasic acids obtained by dimerization of unsaturated fatty acids, or dibasic acids obtained by hydrogenation of dibasic acids obtained by dimerization of unsaturated fatty acids. The unsaturated fatty acid preferably has 18 carbon atoms. Examples of the aforementioned unsaturated fatty acids include oleic acid, linoleic acid, vaccenic acid, elaidic acid, linolenic acid, acrylic acid, and methacrylic acid. The dimer acid may be a dibasic acid obtained by dimerizing one of the unsaturated fatty acids, or a dibasic acid obtained by dimerizing two of the unsaturated fatty acids. The aforementioned unsaturated fatty acid may contain isomers of the main unsaturated fatty acid component.

[0042] The dimer acid may be used individually or as a mixture of two or more types. As the dimer acid, from the viewpoint of suppressing HiP, a dibasic acid obtained by dimerizing one or two selected from the group consisting of oleic acid, linoleic acid, vaccenic acid, elaidic acid, and linolenic acid, or a hydrogenated dibasic acid thereof, is preferred; a dibasic acid obtained by dimerizing oleic acid and linoleic acid, or a hydrogenated dibasic acid thereof, is more preferred; and a hydrogenated dibasic acid obtained by hydrogenating a dibasic acid obtained by dimerizing oleic acid and linoleic acid is even more preferred. The dimer acid may contain, in addition to the dibasic acid which is the main component, monobasic acids and tribasic acids other than dibasic acids.

[0043] The content of the dimer acid is preferably 15 to 87% by mass, more preferably 20 to 85% by mass, and even more preferably 50 to 80% by mass, relative to the total mass of the organic acids. The upper and lower limits within the above range can be combined arbitrarily.

[0044] The content of the dimer acid is preferably 1 to 30% by mass, more preferably 2 to 20% by mass, even more preferably 5 to 15% by mass, and particularly preferably 5 to 10% by mass, relative to the total mass of the flux. The upper and lower limits of the above range can be combined arbitrarily. If the content of the dimer acid is above the lower limit of the preferred range, the generation of HiP can be suppressed. If it is below the upper limit of the preferred range, the water washability is good. If the content of the dimer acid is below the upper limit of the preferred range, void formation can be further suppressed.

[0045] ≪Organic sulfonic acids≫ The water-washing flux according to this embodiment contains an organic sulfonic acid as an organic acid. Examples of organic sulfonic acids include aliphatic sulfonic acids and aromatic sulfonic acids. Examples of aliphatic sulfonic acids include alkanesulfonic acids and alkanolsulfonic acids.

[0046] Examples of alkanesulfonic acids include methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, 2-propanesulfonic acid, 1-butanesulfonic acid, 2-butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid, decanesulfonic acid, and dodecanesulfonic acid. Examples of alkanol sulfonic acids include 2-hydroxyethane-1-sulfonic acid, 2-hydroxypropane-1-sulfonic acid, 2-hydroxybutane-1-sulfonic acid, 2-hydroxypentane-1-sulfonic acid, 1-hydroxypropane-2-sulfonic acid, 3-hydroxypropane-1-sulfonic acid, 4-hydroxybutane-1-sulfonic acid, 2-hydroxyhexane-1-sulfonic acid, 2-hydroxydecane-1-sulfonic acid, and 2-hydroxydodecane-1-sulfonic acid. Examples of aromatic sulfonic acids include 1-naphthalene sulfonic acid, 2-naphthalene sulfonic acid, p-toluenesulfonic acid, xylene sulfonic acid, p-phenolsulfonic acid, cresolsulfonic acid, sulfosalicylic acid, nitrobenzenesulfonic acid, sulfobenzoic acid, and diphenylamine-4-sulfonic acid.

[0047] Organic sulfonic acids may be used individually or in combination of two or more types. Among the above, it is preferable that the organic sulfonic acid includes at least one selected from the group consisting of alkane sulfonic acids and aromatic sulfonic acids.

[0048] The content of organic sulfonic acid is preferably 0.5 to 50% by mass, more preferably 1 to 30% by mass, even more preferably 2 to 25% by mass, and particularly preferably 3 to 20% by mass, relative to the total mass of organic acids. The upper and lower limits within the above range can be combined arbitrarily.

[0049] The content of the organic sulfonic acid is preferably 0.1 to 5% by mass, more preferably 0.1 to 4% by mass, even more preferably 0.2 to 3% by mass, and particularly preferably 0.3 to 2% by mass, relative to the total mass of the flux. The upper and lower limits of the above range can be combined arbitrarily. When the content of the organic sulfonic acid is within the preferred range, the water washability is good and the generation of HiP can be suppressed.

[0050] The mass ratio of the dimer acid to the organic sulfonic acid can be appropriately adjusted, for example, in the range of dimer acid / organic sulfonic acid = 0.5 to 80, but from the viewpoint of HiP control, a ratio of dimer acid / organic sulfonic acid greater than 1.0 and less than or equal to 25 is preferred, and a ratio of dimer acid / organic sulfonic acid greater than 1.0 and less than or equal to 20 is more preferred. When the mass ratio of the dimer acid to the organic sulfonic acid is within the preferred range, the generation of HiP can be suppressed.

[0051] If the mass ratio of the dimer acid to the organic sulfonic acid is greater than 1.0 and less than or equal to 20, even within the preferred range described above, the generation of voids can be further suppressed, and if the mass ratio of the dimer acid to the organic sulfonic acid is greater than 1.0 and less than or equal to 10, the generation of voids can be suppressed even more.

[0052] The total content of the dimer acid and the organic sulfonic acid is preferably 15.5 to 100% by mass, more preferably 35 to 95% by mass, and even more preferably 40 to 90% by mass, relative to the total mass of the organic acids. The upper and lower limits of the above range can be combined arbitrarily.

[0053] The total content of the dimer acid and the organic sulfonic acid is preferably 1.1 to 35% by mass, more preferably 2 to 25% by mass, even more preferably 5 to 18% by mass, and particularly preferably 5 to 12% by mass, based on the total mass of the flux. The upper and lower limits of the above range can be combined arbitrarily.

[0054] <<Other Organic Acids>> The water-washing flux according to this embodiment may contain organic acids other than the dimer acid and the organic sulfonic acid as the organic acid.

[0055] The water-washing flux according to this embodiment preferably further contains a dibasic acid as an organic acid. Examples of dibasic acids include oxalic acid, malonic acid, diglycolic acid, succinic acid, glutaric acid, 2,4-diethylglutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanediic acid, dodecanediic acid, eicosanedioic acid, terephthalic acid, dipicolinic acid, phthalic acid, isophthalic acid, and phenylsuccinic acid.

[0056] As the dibasic acid, from the viewpoint of HiP control, a dibasic acid having 4 or fewer carbon atoms is preferred, at least one selected from the group consisting of oxalic acid, malonic acid, diglycolic acid, and succinic acid is preferred, at least one selected from the group consisting of diglycolic acid and succinic acid is more preferred, and succinic acid is even more preferred.

[0057] The aforementioned dibasic acid may be used individually or as a mixture of two or more types. The content of the dibasic acid is preferably 0 to 50% by mass, more preferably 3 to 45% by mass, and even more preferably 5 to 40% by mass, relative to the total mass of the organic acids. The content of the dibasic acid is preferably 0 to 5% by mass, more preferably 0.1 to 4% by mass, and even more preferably 0.2 to 3% by mass, relative to the total mass of the flux. The upper and lower limits of the above range can be arbitrarily combined. When the content of the dibasic acid is within the preferred range, the generation of HiP can be suppressed.

[0058] If the dibasic acid contains a dibasic acid with 4 or fewer carbon atoms, and its content is within the preferred range, the generation of voids can be further suppressed.

[0059] The total content of the dimer acid, the organic sulfonic acid, and the dibasic acid is preferably 80 to 100% by mass, and more preferably 80 to 98% by mass, relative to the total mass of the organic acids. The total content of the dimer acid, the organic sulfonic acid, and the dibasic acid is preferably 1.1 to 40% by mass, more preferably 2 to 30% by mass, even more preferably 5 to 20% by mass, and particularly preferably 5 to 15% by mass, relative to the total mass of the flux. The upper and lower limits of the above range can be combined in any way.

[0060] Examples of organic acids other than the aforementioned dibasic acids include aliphatic carboxylic acids and aromatic carboxylic acids. Examples of aliphatic carboxylic acids include tartaric acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butanoic acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, isostearic acid, nonadecanoic acid, eicosanoic acid, caproleic acid, lindelic acid, myristoleic acid, palmitic acid Examples include leic acid, oleic acid, elaidic acid, petroceric acid, vaccenic acid, linoleic acid, linolenic acid, eleostearic acid, stearidonic acid, tali-phosphate, ricinoleic acid, 12-hydroxystearic acid, 1,3-cyclohexanedicarboxylic acid, tris(2-carboxyethyl) isocyanurate, hyragonic acid, hydrocarpic acid, verno-phosphate, sterkric acid, trimer acid, and hydrogenated trimer acid, which is a hydrogenated product of trimer acid. Examples of aromatic carboxylic acids include benzoic acid, salicylic acid, 3-hydroxybenzoic acid, 2,3-dihydroxybenzoic acid, p-hydroxyphenylacetic acid, picolinic acid, dibutylaniline diglycolic acid, 2-quinoline carboxylic acid, and p-anisic acid.

[0061] The organic acids other than the dibasic acid may be used individually or in a mixture of two or more. The content of organic acids other than the dibasic acid is preferably 0 to 25% by mass, more preferably 1 to 23% by mass, and even more preferably 2 to 20% by mass, relative to the total mass of organic acids. The content of organic acids other than the aforementioned dibasic acids is preferably 0 to 5% by mass, more preferably 0.1 to 4% by mass, and even more preferably 0.2 to 3% by mass, relative to the total mass of the flux. The upper and lower limits within the above range can be arbitrarily combined.

[0062] The content of the organic acid is preferably 1.1 to 35% by mass, more preferably 3 to 25% by mass, even more preferably 5 to 20% by mass, and particularly preferably 5 to 15% by mass, relative to the total mass of the flux. The upper and lower limits within the above range can be combined in any way.

[0063] <Solvent> The water-washing flux according to this embodiment contains a solvent. Examples of the aforementioned solvents include glycol ether-based solvents, alcohol-based solvents, and ester-based solvents.

[0064] Examples of glycol ether solvents include phenyl glycol (boiling point 237°C), butyl carbitol (boiling point 231°C), diethylene glycol monohexyl ether (boiling point 258°C), diethylene glycol mono-2-ethylhexyl ether (boiling point 272°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), tripropylene glycol monomethyl ether (boiling point 243°C), and tripropylene glycol n-butyl ether (boiling point 274°C).

[0065] Examples of alcohol-based solvents include ethanol (boiling point 78°C), 1-propanol (boiling point 97°C), 2-propanol (boiling point 82°C), 1,2-butanediol (boiling point 192°C), 2,2-dimethyl-1,3-propanediol (boiling point 210°C), 2-methyl-2,4-pentanediol (hexylene glycol) (boiling point 197°C), 2,5-dimethyl-2,5-hexanediol (boiling point 215°C), 2,5-dimethyl-3-hexyne-2,5-diol (boiling point 206°C), 2,3-dimethyl-2,3-butanediol (boiling point 174°C), and 2-methylpentane-2,4-diol. Examples include ol (boiling point 197°C), 1-ethynyl-1-cyclohexanol (boiling point 180°C), 2,4-diethyl-1,5-pentanediol, 1,1,1-tris(hydroxymethyl)propane, 2,2'-oxybis(methylene)bis(2-ethyl-1,3-propanediol), 1,2,6-trihydroxyhexane, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 2,4,7,9-tetramethyl-5-decine-4,7-diol, 2,2-bis(hydroxymethyl)-1,3-propanediol, isobornylcyclohexanol, and the like. Examples of ester-based solvents include bis(2-ethylhexyl) sebacate.

[0066] The aforementioned solvent may be used individually or as a mixture of two or more types. As for the solvent, from the viewpoint of suppressing voids and improving printability, it is more preferable to include a solvent with a boiling point of 260°C or higher, and it is even more preferable to include diethylene glycol mono-2-ethylhexyl ether (boiling point 272°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), and tripropylene glycol n-butyl ether (boiling point 274°C).

[0067] The solvent content is preferably 10 to 70% by mass, more preferably 15 to 60% by mass, and even more preferably 15 to 50% by mass, based on the total mass of the flux.

[0068] The total content of the water-soluble base agent and the solvent is preferably 25 to 98.9% by mass, more preferably 30 to 90% by mass, and more preferably 40 to 70% by mass, based on the total mass of the flux. The upper and lower limits of the above range can be combined arbitrarily.

[0069] <Other ingredients> In this embodiment, the water-washing flux may contain, as necessary, other components in addition to the water-soluble base agent selected from the nonionic surfactants, the organic acid, and the solvent. Other components include amines, halogen compounds and other activators, metal deactivators, silane coupling agents, antioxidants, colorants, and resin components.

[0070] ≪Amine≫ Examples of amines include azoles, guanidines, alkylamine compounds, amino alcohol compounds, and amine polyoxyalkylene adducts.

[0071] Examples of azoles include 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, and 1-cyanoethyl-2-ethylimidazole. Tyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl- s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanurate adduct, 2-phenylimidazole isocyanurate adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazole Phosphorus, 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, 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 Examples include 1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, carboxybenzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, 2,2'-[[(methyl-1H-benzotriazole-1-yl)methyl]imino]bisethanol, 1-(1',2'-dicarboxyethyl)benzotriazole, 1-(2,3-dicarboxypropyl)benzotriazole, 1-[(2-ethylhexylamino)methyl]benzotriazole, 2,6-bis[(1H-benzotriazole-1-yl)methyl]-4-methylphenol, 5-methylbenzotriazole, 5-phenyltetrazole, etc.

[0072] 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.

[0073] Examples of alkylamine compounds include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, and stearylamine.

[0074] Examples of amino alcohol compounds include monoisopropanolamine, N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine, and N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine.

[0075] Examples of amine polyoxyalkylene adducts include terminal diamine polyalkylene glycols, aliphatic amine polyoxyalkylene adducts, and aromatic amine polyoxyalkylene adducts. Examples of alkylene oxides derived from amine polyoxyalkylene adducts include ethylene oxide, propylene oxide, and butylene oxide.

[0076] Terminal diamine polyalkylene glycols are compounds in which both ends of a polyalkylene glycol are aminated. Examples of terminally diamine polyalkylene glycols include terminally diamine polyethylene glycol, terminally diamine polypropylene glycol, and terminally diamine polyethylene glycol-polypropylene glycol (PEG-PPG) copolymer. Examples of terminal diamine 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.

[0077] Aliphatic amine polyoxyalkylene adducts and aromatic amine polyoxyalkylene adducts are formed in which a polyoxyalkylene group is bonded to the nitrogen atom of an amine. Examples of the amines mentioned above include ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, hexamethylenediamine, laurylamine, stearylamine, oleylamine, tallowamine, hydrogenated tallowamine, tallowpropyldiamine, diethylenetriamine, metaxyldiamine, paraxyldiamine, isophoronediamine, 1,10-decanediamine, 1,12-dodecanediamine, 4,4-diaminodicyclohexylmethane, tolylenediamine, butane-1,1,4,4-tetraamine, pyrimidine-2,4,5,6-tetraamine, phenylenediamine, 4,4-diaminodiphenylmethane, and the like.

[0078] The aforementioned amine may be used individually or as a mixture of two or more types. Among the above, the aforementioned amines are: Preferably, it contains at least one selected from the group consisting of azoles, amino alcohol compounds, and amine polyoxyalkylene adducts. It is more preferable to include azoles and at least one selected from the group consisting of amino alcohol compounds and amine polyoxyalkylene adducts. It is even more preferable to include azoles, amino alcohol compounds, and amine polyoxyalkylene adducts.

[0079] As the amine, among azoles, imidazole compounds are preferred, including alkyl-substituted imidazole compounds such as 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, and 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-phenylimidazole. It is more preferable to use at least one compound selected from the group consisting of phenyl group-substituted imidazole compounds such as zyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazolium trimelate, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, and 2-phenyl-4-methyl-5-hydroxymethylimidazole, and it is even more preferable to use at least one compound selected from the group consisting of 2-ethylimidazole and 2-phenylimidazole.

[0080] As the amine, it is preferable to use at least one selected from the group consisting of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine and N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, and it is more preferable to use N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine.

[0081] As the amine, it is preferable to use at least one selected from the group consisting of terminal diamine polyalkylene glycols and aliphatic amine polyoxyalkylene adducts, and more preferably at least one selected from the group consisting of terminal diamine polyethylene glycol-polypropylene glycol (PEG-PPG) copolymers and polyoxyethylene stearylamine.

[0082] The content of the azoles is preferably 1 to 15% by mass, more preferably 3 to 13% by mass, and even more preferably 5 to 10% by mass, relative to the total mass of the amines. The content of the azoles is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, and even more preferably 1 to 3% by mass, relative to the total mass of the flux. The upper and lower limits of the above range can be combined arbitrarily.

[0083] The content of the amino alcohol compound is preferably 0 to 95% by mass, more preferably 20 to 75% by mass, and even more preferably 35 to 55% by mass, relative to the total mass of the amine. The content of the amino alcohol compound is preferably 0 to 30% by mass, more preferably 5 to 25% by mass, and even more preferably 7 to 23% by mass, relative to the total mass of the flux. The upper and lower limits within the above range can be combined in any way.

[0084] The content of the amine polyoxyalkylene adduct is preferably 0 to 95% by mass, more preferably 20 to 80% by mass, and even more preferably 40 to 60% by mass, based on the total mass of the amine. The content of the amine polyoxyalkylene adduct is preferably 0 to 30% by mass, more preferably 5 to 25% by mass, and even more preferably 7 to 23% by mass, relative to the total mass of the flux. The upper and lower limits within the above range can be combined in any way.

[0085] The amine content is preferably 15 to 40% by mass, and more preferably 20 to 35% by mass, relative to the total mass of the flux. The upper and lower limits of the range can be combined arbitrarily.

[0086] The total content of the water-soluble base agent, the solvent, and the amine is preferably 65 to 98.9% by mass relative to the total mass of the flux.

[0087] ≪Halogen compounds≫ Examples of halogen compounds include amine hydrohalides and organic halogen compounds other than amine hydrohalides.

[0088] Amine hydrohalides are compounds formed by reacting an amine with a hydrogen halide. Examples of amines used here include aliphatic amines, azoles, and guanidines. Examples of hydrogen halides include chlorine, bromine, and iodine hydrides. Examples of aliphatic amines include ethylamine, diethylamine, triethylamine, and ethylenediamine. Examples of guanidines and azoles include those mentioned above in the amine category.

[0089] 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, dimethylamine hydrobromide, and dimethylamine hydrobromide. Hydrochloride, rosinamine hydrobromide, 2-ethylhexylamine hydrochloride, isopropylamine hydrochloride, cyclohexylamine hydrochloride, 2-pipecolin 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 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 dibromide, rosinamine hydrobromide, 2-phenylimidazole hydrobromide, 4-benzyl Examples include pyridine hydrobromide, L-glutamate hydrochloride, N-methylmorpholine hydrochloride, betaine hydrochloride, 2-pipecolin hydroiodide, cyclohexylamine hydroiodide, 1,3-diphenylguanidine hydrofluoric acid, diethylamine hydrofluoric acid, 2-ethylhexylamine hydrofluoric acid, cyclohexylamine hydrofluoric acid, ethylamine hydrofluoric acid, rosinamine hydrofluoric acid, cyclohexylamine tetrafluoroborate, and dicyclohexylamine tetrafluoroborate.

[0090] Furthermore, halogen compounds such as salts obtained by reacting amines with tetrafluoroboric acid (HBF4) and complexes obtained by reacting amines with boron trifluoride (BF3) can also be used. Examples of the aforementioned complexes include boron trifluoride piperidine.

[0091] Examples of organic 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 aliphatic hydrocarbon group are replaced by halogen atoms. Examples of halogenated aliphatic compounds include halogenated aliphatic alcohols and halogenated heterocyclic compounds.

[0092] 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.

[0093] Examples of heterocyclic halogenated compounds include compounds represented by the following general formula (1).

[0094] R 21 -(R 22 ) n (1) [In the formula, R 21 R represents an n-valence heterocyclic group. 22 This represents a halogenated aliphatic hydrocarbon group.

[0095] R 21In this context, the heterocyclic group of the n-valent heterocyclic group can be described as 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, nitrogen atoms, etc. This heterocyclic ring is preferably a 3- to 10-membered ring, and more preferably a 5- to 7-membered ring. Examples of such complex rings include isocyanurate rings. R 22 In this, the halogenated aliphatic hydrocarbon group is preferably having 1 to 10 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably 3 to 5 carbon atoms. Also, R 22 The group is preferably a brominated aliphatic hydrocarbon group or a chlorinated aliphatic hydrocarbon group, more preferably a brominated aliphatic hydrocarbon group, and even more preferably a brominated saturated aliphatic hydrocarbon group. Examples of halogenated heterocyclic compounds include tris-(2,3-dibromopropyl)isocyanurate.

[0096] In addition, examples of organic halogen compounds other than amine hydrohalides include iodized carboxyl compounds such as 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, and 5-iodoanthranilic acid; chloride carboxyl compounds such as 2-chlorobenzoic acid and 3-chloropropionic acid; and halogenated carboxyl compounds such as brominated carboxyl compounds such as 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid, and 2-bromobenzoic acid. Halogen compounds may be used individually or in combination of two or more.

[0097] ≪Metal deactivator≫ Examples of metal deactivators include hindered phenol compounds and nitrogen compounds. In this context, "metal deactivator" refers to a compound that has the property of preventing metal degradation upon contact with certain compounds.

[0098] Hindered phenol compounds are phenol compounds that have a bulky substituent (for example, a branched or cyclic alkyl group such as a t-butyl group) at at least one of the ortho positions of the phenol. The hindered phenol compounds are not particularly limited and include, for example, 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-hexanediolbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 2,2'-methylenebis [6-(1-methylcyclohexyl)-p-cresol], 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-bi Su-(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 Examples include '-hexamethylenebis(3,5-di-t-butyl-4-hydroxyhydrocinnamamide), 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, and N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxamide.

[0099] Examples of nitrogen compounds used as metal deactivators include hydrazide-based nitrogen compounds, amide-based nitrogen compounds, triazole-based nitrogen compounds, and melamine-based nitrogen compounds.

[0100] Examples of hydrazide nitrogen compounds include any nitrogen compound having a hydrazide skeleton, such as bis[N2-(2-hydroxybenzoyl)hydrazide] dodecanediate, N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, disalithyroyl hydrazide decanedicarboxylic acid, N-salicylidene-N'-salicyl hydrazide, m-nitrobenzhydrazide, 3-aminophthalhydrazide, phthalate dihydrazide, adipic acid hydrazide, oxalobis(2-hydroxy-5-octylbenzylidene hydrazide), N'-benzoylpyrrolidone carboxylic acid hydrazide, and N,N'-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hydrazine.

[0101] Any nitrogen compound having an amide skeleton can be used, such as N,N'-bis{2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxyl]ethyl}oxamide.

[0102] Triazole nitrogen compounds can be any nitrogen compounds having a triazole skeleton, such as N-(2H-1,2,4-triazole-5-yl)salicylamide, 3-amino-1,2,4-triazole, and 3-(N-salicyloyl)amino-1,2,4-triazole.

[0103] Any nitrogen compound having a melamine skeleton can be used, 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. The metal deactivator may be used alone or in a mixture of two or more types.

[0104] ≪Resin components≫ The water-washing flux according to this embodiment preferably does not contain resin components from the viewpoint of improving water-washability. In this specification, examples of resin components include rosin, resins other than rosin, and the like.

[0105] In this specification, "rosin" includes natural resins containing abietic acid as the main component, mixtures of abietic acid and its isomers, and chemically modified natural resins (sometimes referred to as rosin derivatives).

[0106] The abietic acid content in natural resins is, for example, between 40% and 80% by mass relative to the natural resin. In this specification, "main component" refers to a component that makes up a compound and is present in an amount of 40% by mass or more.

[0107] Representative isomers of abietic acid include neoabietic acid, palastic acid, and levopimaric acid.

[0108] Examples of the aforementioned "natural resins" include gum rosin, wood rosin, and tall oil rosin.

[0109] In the present invention, "natural resins that have been chemically modified (rosin derivatives)" include those obtained by subjecting the "natural resin" to one or more treatments selected from the group consisting of hydrogenation, dehydrogenation, neutralization, amidation, dimerization and polymerization, esterification, and Diels-Alder cycloaddition.

[0110] Examples of rosin derivatives include purified rosin and modified rosin. Examples of modified rosins include hydrogenated rosin, polymerized rosin, polymerized hydrogenated rosin, disproportionated rosin, acid-modified rosin, rosin esters, acid-modified hydrogenated rosin, acid-modified hydrogenated rosin, acid-modified disproportionated rosin, acid-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, hydrated and disproportionated products of the polymerized rosin, and purified, hydrated and disproportionated products of the α,β-unsaturated carboxylic acid modified products, rosin alcohol, rosin amine, hydrogenated rosin alcohol, rosin esters, hydrogenated rosin esters, rosin soap, hydrogenated rosin soap, acid-modified rosin soap, and the like.

[0111] Examples of rosinamines include dehydroabiethylamine and dihydroabiethylamine. Rosinamine refers to so-called disproportionated rosinamines.

[0112] Examples of resins 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 other thermosetting resins. Examples of modified terpene resins include aromatic modified terpene resins, hydrogenated terpene resins, and hydrogenated aromatic modified terpene resins. Examples of modified terpene phenol resins include hydrogenated terpene phenol resins. Examples of modified styrene resins include styrene acrylic resins and styrene maleic acid resins. Examples of modified xylene resins include phenol modified xylene resins, alkylphenol modified xylene resins, phenol modified resol-type xylene resins, polyol modified xylene resins, and polyoxyethylene-added xylene resins.

[0113] Other thermosetting resins include, for example, epoxy resins. Examples of epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, glycidylamine type resin, alicyclic epoxy resin, aminopropane type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, anthracene type epoxy resin, triazine type epoxy resin, dicyclopentadiene type epoxy resin, triphenylmethane type epoxy resin, fluorene type epoxy resin, phenol aralkyl type epoxy resin, and novolac type epoxy resin. The flux according to this embodiment is more suitable as a flux for water washing because it does not contain at least one resin component selected from the group consisting of rosin and thermosetting resins.

[0114] The water-washing flux according to this embodiment described above contains a water-soluble base agent selected from nonionic surfactants, an organic acid, and a solvent. The organic acid includes dimer acid and organic sulfonic acid, thereby providing excellent water-washing properties and suppressing the generation of HiP. The water-washing flux according to this embodiment contains a nonionic surfactant, which increases its affinity for water and improves the water-washability of the flux residue. The water-washing flux according to this embodiment contains dimer acid and organic sulfonic acid as organic acids. Generally, dimer acid has low affinity for water and reduces water-washing performance, so it is not actively used in water-washing fluxes. Furthermore, containing only organic sulfonic acid is insufficient to improve the water-washing performance of the flux residue, and it is difficult to suppress the generation of HiP. However, surprisingly, we found that combining dimer acid and organic sulfonic acid as organic acids can suppress the generation of HiP while maintaining water-washing performance, and this combination was adopted. The reason for this effect is not clear, but it is presumed to be as follows. In solder paste using this flux, the viscosity of the molten solder paste increases, improving its ability to follow solder balls, thus suppressing the occurrence of HiP (High-Intensity Plasma). Furthermore, by including dimer acid and organic sulfonic acid as organic acids, the heat resistance of the activator in the flux increases, further suppressing the occurrence of HiP.

[0115] The water-washing flux according to this embodiment further has the effect of suppressing void formation and exhibiting excellent printability. The reason for these effects is thought to be that the inclusion of dimer acid and organic sulfonic acid as organic acids improves flux activity, making it easier for voids to be discharged from the solder paste. In addition, since the water-washing flux according to this embodiment contains a nonionic surfactant, the thixotropy of the solder paste using this flux is increased, which is thought to result in excellent printability.

[0116] (Solder paste for water washing) The solder paste according to this embodiment contains the above-mentioned water-washing flux and solder alloy powder.

[0117] The solder alloy powder may consist of powdered solder made of elemental Sn, or powdered solder alloys such as Sn-Ag, Sn-Cu, Sn-Ag-Cu, Sn-Bi, Sn-In, or these alloys to which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. are added. The solder alloy powder may consist of a Sn-Pb system, or a solder alloy powder in which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. are added to the Sn-Pb system. The solder alloy powder is preferably a lead-free solder. As the solder alloy powder, for example, one with a melting point of 150 to 250°C can be used.

[0118] The content of water-washing flux in the solder paste is preferably 5 to 30% by mass, and more preferably 5 to 15% by mass, relative to the total mass of the solder paste.

[0119] The solder paste according to this embodiment contains the above-mentioned water-washing flux, It offers excellent water-cleanability and has the effect of suppressing the generation of HiP (High-Intensity Pulsation). The solder paste according to this embodiment further has the effect of suppressing the generation of voids and exhibiting excellent printability.

[0120] In another aspect, the present invention further encompasses the following embodiments.

[0121] [8] The water washing flux according to any one of [1] to [6], wherein the nonionic surfactant comprises at least one selected from the group consisting of aliphatic alcohol polyoxyethylene adducts and aromatic alcohol polyoxyethylene adducts.

[0122] [9] A water washing flux according to any one of [1] to [6] and [8], further comprising an amine.

[0123]

[10] The water washing flux according to [9], wherein the amine comprises azoles and amine polyoxyalkylene adducts.

[0124] A solder paste for water washing containing a water washing flux described in any one of items

[11] [8] to

[10] and solder alloy powder. [Examples]

[0125] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0126] <Preparation of flux> (Examples 1-16, Comparative Examples 1-7) Fluxes for the examples and comparative examples were prepared with the compositions shown in Tables 1 to 5. Note that Example 1 in Tables 1 to 4 is the same. In the tables, the content of each component is shown as a percentage (mass%) relative to the total mass (100 mass%) of the flux. The raw materials used are listed below.

[0127] Water-soluble base agent: Nonionic surfactants (1) Behenyl alcohol EO adduct (BLAUNON® BE-30, manufactured by Aoki Oil & Fat Industry Co., Ltd.) (2) Polyethylene glycol (PEG-4000S, manufactured by Sanyo Chemical Industries, Ltd., average molecular weight: 3364) (3) Resorcinol EO adduct (BARREL® Barrel Process Oil GR-175, manufactured by Matsumura Oil Co., Ltd.)

[0128] Organic acids: • Dimer acid (1) C18-C18 hydrogenated dimer acid (reaction product of oleic acid and linoleic acid) • Organic sulfonic acid (1) Methanesulfonic acid (2) p-toluenesulfonic acid ·Dibasic acid (1) Diglycolic acid (2) succinic acid (3) Glutaric acid Other organic acids: (1) 2,2-Bis(hydroxymethyl)propionic acid (2) Oleic acid (C18 carboxylic acid)

[0129] solvent: Tripropylene glycol-n-butyl ether (boiling point: 274°C) Diethylene glycol monohexyl ether (boiling point: 259°C)

[0130] Other ingredients: •amine (1) 2-Ethylimidazole (2) 2-phenylimidazole (3) Terminal diamine polyethylene glycol-polypropylene glycol copolymer (JEFFAMINE® ED600, manufactured by HUNTSMAN Corporation) (4) N,N,N',N'-Tetrakis(2-hydroxypropyl)ethylenediamine (amino alcohol EDA-P4, manufactured by Nippon Emulsifier Co., Ltd.) (5) Polyoxyethylene stearylamine (Newcol® OD-420, Nippon Emulsifier Co., Ltd.)

[0131] <Preparation of Solder Paste> Solder paste was prepared by mixing the flux from each example with the solder alloy powder described below. In all of the prepared solder pastes, the flux was 10.5% by mass and the solder alloy powder was 89.5% by mass.

[0132] The solder alloy powder in the solder paste is a powder consisting of a solder alloy with 3% by mass of Ag, 0.5% by mass of Cu, and the remainder being Sn. The solidus temperature of this solder alloy is 217°C, and the liquidus temperature is 219°C. The solder alloy powder has a size (particle size distribution) that satisfies symbol 4 in the powder size classification (Table 2) of JIS Z 3284-1:2014.

[0133] <Rating> The water washability and HiP of the solder pastes using the fluxes of Example 1 and Comparative Examples 1-5 were evaluated under the following conditions. The results are shown in Table 1. The solder pastes using the fluxes of Examples 1-16 and Comparative Examples 6-7 were evaluated for water washability, HiP, voids, and printability under the following conditions. The results are shown in Tables 2-5.

[0134] [Evaluation of water washability] The following printed circuit board was used. Printed circuit board: Material FR-4, thickness 1.6mm, land dimensions 0.25mm x 0.50mm, land spacing for the same chip area is 0.50mm in the short side direction, land spacing between adjacent chip areas is 0.1mm in the long side direction and 0.1mm in the short side direction.

[0135] The prepared solder paste was printed onto a printed circuit board using a 0.08 mm thick metal mask. A 1005 Chip Capacitor (1005CC, dimensions 1.0 mm x 0.50 mm) component was mounted onto the printed circuit board, and soldered by reflow soldering at an oxygen concentration of 1000 ppm or less. Figure 1 shows the reflow profile. The reflow profile involved raising the temperature from 130°C to 220°C over 90 seconds, holding it above 220°C for 42 seconds, with a peak temperature of 242°C. The reflow-treated substrates were placed in an ultrasonic cleaning tank containing distilled water at 25-30°C and ultrasonically cleaned at 40kHz for 10 minutes. After cleaning, the substrates were dried with compressed air. Next, the 1005CC components were removed, and the cleaning residue beneath the chips was observed using a scanning electron microscope (SEM) and an optical microscope. The number of cleaning residues that remained connected (bridged) from one electrode to an adjacent electrode under the same chip was checked, and the ratio of the number of bridges to the total number of chips (128) was defined as the cleaning failure rate (%). Cleaning failure rate (%) = Number of bridges (pieces) / Total number of chips 128 (pieces) × 100

[0136] Judgment criteria: A: Cleaning failure rate: 0% B: Cleaning failure rate: greater than 0% but less than 5% C: Cleaning failure rate 5% to less than 10% D: Cleaning failure rate 10% to less than 20% E: Cleaning failure rate of 20% or more Fluxes that received an evaluation result of A to C were deemed to pass, while those that received a D or E were deemed to fail.

[0137] [HiP's evaluation] The following printed circuit boards and BGA components were used. Printed circuit board: Material FR-4, thickness 0.8mm, land dimensions: diameter 0.24mm BGA component: Component size 13mm x 13mm, thickness 0.5mm, bump composition M705 (Sn-3.0Ag-0.5Cu), bump size 0.25mm, number of bumps (I / O) 432 x number of components 3 = total number of bumps 1296 BGA pretreatment: The BGA components were subjected to a heat treatment at 85°C / 85% RH for 24 hours, followed by a further heat treatment at 125°C for 1 hour.

[0138] The prepared solder paste was printed onto a printed circuit board using a 0.08 mm thick metal mask. BGA components were mounted onto the printed circuit board and soldered by reflow soldering at an oxygen concentration of 1000 ppm or less. The reflow soldering was performed under the same conditions as the reflow profile used in the [Evaluation of Water Washability] section above. After reflowing, the BGA components were removed from the substrate, and the bonding condition of the bumps was observed using an optical microscope to determine the number of defective bonds out of a total of 1296 bumps.

[0139] Judgment criteria: A: Number of defective connections: 0 B: Number of defective joints: 1 or more but less than 5 C: Number of defective joints: 5 or more but less than 20 D: Number of defective joints: 20 or more but less than 30 E: 30 or more defective connections Fluxes that received an evaluation result of A to C were deemed to pass, while those that received a D or E were deemed to fail.

[0140] [Void's evaluation] The following printed circuit boards and BGA components were used. Printed circuit board: Material FR-4, thickness 1.6mm, land dimensions 0.3mm in diameter BGA component: Component size 8mm x 8mm, thickness 1.1mm, bump composition M705 (Sn-3.0Ag-0.5Cu), bump size 0.3mm, number of bumps (I / O) 132 x number of components 3 = total number of bumps 396

[0141] The prepared solder paste was printed onto a printed circuit board using a 0.08 mm thick metal mask. After printing, BGA components were mounted onto the printed circuit board and soldered by reflow soldering at an oxygen concentration of 1000 ppm or less. The reflow soldering was performed under the same conditions as the reflow profile used in the [Evaluation of Water Washability] section above. In the measurement of void area, if an X-ray passed through at least one void, it was considered that a void was present. Voids with a diameter of 0.1 μm or larger were detected. The area of ​​voids generated at the joints between bumps and lands was measured by irradiating the reflowed bond with X-rays from the vertical direction of the substrate and analyzing the transmitted X-rays. An XD7600NT Diamond X-ray inspection system (Nordson DAGE) was used for the measurement. Next, the ratio of void area to bump area (void area ratio) was calculated, and the maximum value of the void area ratio (%) among the total number of bumps (396) was confirmed.

[0142] Judgment criteria: A: Maximum void area ratio less than 5% B: Maximum void area ratio 5% or more but less than 10% C: Maximum void area ratio 10% or more but less than 15% D: Maximum void area ratio 15% or more but less than 20% E: Maximum void area ratio of 20% or more Fluxes that received an evaluation result of A to C were deemed to pass, while those that received a D or E were deemed to fail.

[0143] [Evaluation of printability] The following printed circuit board was used. Printed circuit board: Material FR-4, thickness 1.6mm, land dimensions 0.25mm x 0.50mm, land spacing 0.1mm in the long side direction, 0.1mm or 0.5mm in the short side direction.

[0144] The prepared solder paste was printed onto a printed circuit board using a 0.08 mm thick metal mask. The printed board was observed with an optical microscope to determine the solder paste bridging rate (%) out of a total of 128 lands.

[0145] Judgment criteria: A: Bridge occurrence rate 0% B: Bridge occurrence rate greater than 0% but less than 5% C: Bridge occurrence rate 5% to less than 10% D: Bridge occurrence rate 10% to less than 20% E: Bridge occurrence rate of 20% or more Fluxes that received an evaluation result of A to C were deemed to pass, while those that received a D or E were deemed to fail.

[0146] [Table 1]

[0147] When the flux from Example 1, which contains dimer acid and organic sulfonic acid as organic acids, was used, water washability was good and HiP generation was suppressed. When the flux of Comparative Example 3, which does not contain either dimer acid or organic sulfonic acid as an organic acid, was used, HiP generation increased, resulting in a D rating.

[0148] When the flux of Comparative Example 2, which does not contain dimer acid as an organic acid but contains organic sulfonic acid, was used, HiP generation increased, resulting in a D rating. When the flux of Comparative Example 4 was used, which replaced the dimer acid of Example 1 with oleic acid (a monocarboxylic acid with 18 carbon atoms) in the same amount, HiP generation increased, resulting in an E rating.

[0149] When the flux of Comparative Example 1, which contains dimer acid as an organic acid but does not contain organic sulfonic acid, was used, the water washability decreased, resulting in a rating of D. When the flux of Comparative Example 5, which used glutaric acid instead of the organic sulfonic acid of Example 1, was used, HiP generation increased, resulting in a D rating.

[0150] [Table 2]

[0151] When the fluxes of Examples 1 to 5, in which the mass ratio of dimer acid to organic sulfonic acid was varied, were used, all exhibited good water washability and suppressed HiP generation. Among the above examples, when using the fluxes of Examples 4, 1, and 3, in which the mass ratio of dimer acid to organic sulfonic acid was 2.7 to 25, HiP generation was further suppressed. Furthermore, among the above examples, when the fluxes of Examples 5, 4, and 1 were used, in which the mass ratio of dimer acid to organic sulfonic acid was 0.5 to 5.3, void generation was suppressed even more effectively.

[0152] [Table 3]

[0153] When using the flux of Example 1, HiP and void formation were more suppressed compared to when using the flux of Example 6, which contained glutaric acid instead of succinic acid in Example 1. Furthermore, when using the flux of Example 1, void formation was more suppressed and printability was better compared to when using the flux of Example 7, which contained diethylene glycol monohexyl ether (boiling point: 259°C) instead of tripropylene glycol-n-butyl ether (boiling point: 274°C) in Example 1.

[0154] [Table 4]

[0155] [Table 5]

[0156] In Tables 4 and 5, when fluxes from Examples 8 to 16, which contained dimer acid and organic sulfonic acid as organic acids and had various other components modified, were used, the water washability was good, HiP generation was suppressed, void generation was suppressed, and printability was good. When the flux of Comparative Example 6, which does not contain dimer acid as an organic acid, was used, HiP generation increased compared to when the fluxes of Examples 1 to 16 were used, resulting in an E rating. The flux used in Comparative Example 7 was the flux described in Prior Art 1, but compared to the case where the fluxes of Examples 1 to 16 were used, the occurrence of HiP increased, resulting in an E rating.

[0157] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Additions, omissions, substitutions, and other modifications to the configuration are possible without departing from the spirit of the present invention. The present invention is not limited by the foregoing description and is limited only by the appended claims.

Claims

1. It contains a water-soluble base agent selected from nonionic surfactants, an organic acid, and a solvent. The aforementioned organic acid is a water-washing flux containing dimer acid and organic sulfonic acid.

2. The content of the dimer acid is 1 to 30% by mass relative to the total mass of the water washing flux. The water washing flux according to claim 1, wherein the content of the organic sulfonic acid is 0.1 to 5% by mass with respect to the total mass of the water washing flux.

3. The mass ratio of the dimer acid to the organic sulfonic acid is, The water washing flux according to claim 2, wherein the ratio of the dimer acid to the organic sulfonic acid is greater than 1.0 and less than or equal to 20.

4. The water washing flux according to claim 1, wherein the organic acid further comprises a dibasic acid having 4 or fewer carbon atoms.

5. The water washing flux according to claim 4, wherein the content of the dibasic acid having 4 or fewer carbon atoms is greater than 0% by mass and less than or equal to 5% by mass, relative to the total mass of the water washing flux.

6. The water washing flux according to claim 1, wherein the boiling point of the solvent is 260°C or higher.

7. A solder paste for water cleaning, comprising a water-cleaning flux according to any one of claims 1 to 6 and solder alloy powder.

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