Water-cleanable flux and water-cleanable solder paste

Abstract

To provide a flux that has excellent water-cleanability for flux residue and can suppress the occurrence of head-in-pillow defects called HiP (Head in Pillow) in the mounting of BGA (Ball Grid Array), CSP (Chip Size Package), etc., and a solder paste containing the flux. SOLUTION: A water-cleanable flux is employed, which contains a water-soluble base agent selected from nonionic surfactants, an organic acid, and a solvent, and the organic acid includes a dimer acid and an organic sulfonic acid.

Description

[Technical Field]

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

[0002] Fixing components to a board and electrically connecting the components to the board are generally performed by soldering, which uses flux, solder powder, and a solder paste made by mixing the flux and solder powder. In soldering using solder paste, the solder paste is first printed on a board, components are then mounted, and the board with the components mounted is heated in a heating furnace called a reflow furnace, which melts the solder powder contained in the solder paste and solders the components to the board.

[0003] Flux chemically removes metal oxides present in the solder and the metal surfaces of the objects being soldered, allowing the movement 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.

[0004] Generally, flux contains resin components, solvents, activators, thixotropic agents, etc. To improve the reliability of the bond between the solder and the object to be joined, excess flux (flux residue) after soldering is sometimes removed by cleaning. Flux remaining after cleaning is called cleaning residue. Cleaning residues may cause a decrease in insulation properties due to ion migration or corrosion of the substrate, or may impair the adhesion of materials during subsequent processes such as wire bonding, underfill insertion, or moisture-proof coating.

[0005] Conventionally, rosin, which has excellent electrical insulation properties and moisture resistance, has been used as the resin component in flux. However, fluxes containing rosin require organic solvents as cleaning solutions for cleaning after soldering, which can cause safety and environmental problems. Therefore, there is a demand for water-cleanable fluxes that can be easily cleaned with water after soldering. In response to this, Patent Document 1 describes a flux containing an organic sulfonic acid activator and a nonionic surfactant with a specific mass average molecular weight. The flux described in Patent Document 1 is said to improve cleanability with water after soldering. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-086400 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, with the trend toward high-density mounting, the gaps under chip components have become increasingly narrow. This makes it difficult for cleaning solutions to reach these narrow gaps, posing a problem for flux cleanability. 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 pattern as electrodes. When mounting BGA and CSP, head-in-pillow defects known as HiP (Head-in-Pillow) can be a problem due to factors such as low flux activity and package warpage during mounting. In contrast, the solder paste using the flux described in Patent Document 1 has sufficient water washability for flux residue, but it is difficult to suppress the occurrence of HiP.

[0008] Therefore, an object of the present invention is to provide a flux that has excellent water cleanability and can suppress the occurrence of HiP, and a solder paste containing the flux. [Means for solving the problem]

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

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

[0011] [3] The flux for cleaning with water 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 flux for cleaning with water according to any one of [1] to [3], wherein the organic acid further contains a dibasic acid having four or less carbon atoms.

[0013] [5] The flux for water cleaning according to [4], wherein the content of the dibasic acid having 4 or less carbon atoms is more than 0 mass % and 5 mass % or less, based on the total mass of the flux for water cleaning.

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

[0015] [7] A water-cleanable solder paste containing the water-cleanable flux according to any one of [1] to [6] and a solder alloy powder. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a flux that has excellent water cleanability and can suppress the occurrence of HiP, and a solder paste containing the flux. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 10 is a diagram showing a reflow profile in the evaluation of the examples. DETAILED DESCRIPTION OF THE INVENTION

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

[0019] In this 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] (Water-cleanable flux) The flux for water cleaning according to this embodiment contains a water-soluble base agent selected from nonionic surfactants, an organic acid, and a solvent. In this specification, the term "water-cleanable flux" refers to a flux whose flux residue can be removed by washing with water. To remove the flux residue by water washing, the water-cleanable flux according to this embodiment contains a water-soluble base agent, which is a component with high affinity for water, and a solvent. Hereinafter, the water-cleanable flux may be simply referred to as "flux."

[0021] <Water-soluble base agent> The water-soluble base agent is a component that exhibits affinity with water. A component that exhibits affinity for water is a component that has a chemical species that exhibits affinity for water. A chemical species that has an affinity for water is a chemical species that forms hydrogen bonds with water. Examples of chemical species that form hydrogen bonds with water include atoms such as oxygen atoms and nitrogen atoms, and functional groups having these atoms. Examples of functional groups having a chemical species that exhibits affinity for water include a hydroxy group, a carboxy group, an amino group, a carbonyl group, an ether bond, an ester bond, an amide bond, -N=, and a cyano group.

[0022] The flux for water cleaning 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 from which polyoxyalkylene adducts are derived include ethylene oxide (EO) and propylene oxide (PO). Examples of the 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 the alcohol in the polyoxyalkylene adduct of alcohol include aliphatic alcohols and aromatic alcohols. Examples of the 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 aromatic alcohol include phenol, benzyl alcohol, p-cumylphenol, naphthol, octylphenol, nonylphenol, dodecylphenol, and resorcinol.

[0025] Examples of the polyoxyalkylene adduct of carboxylic acid include polyoxyalkylene esters.

[0026] Examples of the polyoxyalkylene adduct of carboxylic acid amide include polyoxyalkylene alkylamide.

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

[0028] As the water-soluble base agent, among polyalkylene glycols, polyethylene glycol is preferably used.

[0029] As the water-soluble base agent, among polyoxyalkylene adducts of aliphatic alcohols, it is preferable to use an ethylene oxide (EO) adduct of 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 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 it is even more preferable to use 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 ranges can be combined in any desired manner.

[0031] The content of the alcohol polyoxyalkylene adduct 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 ranges can be combined in any desired manner.

[0032] The content of the polyoxyalkylene adduct of an aliphatic alcohol is preferably 10 to 100% by mass, more preferably 20 to 75% by mass, and even more preferably 30 to 60% by mass, based on the total mass of the water-soluble base agent. The upper and lower limits of the above ranges can be combined in any manner. When the content of the polyoxyalkylene adduct of an aliphatic alcohol is within the above-mentioned 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, based on the total mass of the water-soluble base agent. The upper and lower limits of the ranges can be combined in any manner. When the content of the polyoxyalkylene adduct of aromatic alcohol is within the above-mentioned 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 content of the polyoxyalkylene adduct of an aromatic alcohol (mass of polyoxyalkylene adduct of aliphatic alcohol / mass of polyoxyalkylene adduct of 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 of the above ranges can be combined in any desired manner.

[0035] The content of the water-soluble base agent is preferably 5 to 75 mass %, more preferably 10 to 65 mass %, even more preferably 15 to 55 mass %, and particularly preferably 15 to 45 mass %, relative to the total mass of the flux. The upper and lower limits of the ranges can be combined in any manner. When the content of the water-soluble base agent is equal to or greater than the lower limit of the preferred range, water washability is improved.

[0036] The content of the polyalkylene glycol is preferably 0 to 30 mass %, more preferably 0 to 20 mass %, further preferably 0 to 15 mass %, and particularly preferably 0 to 10 mass %, relative to the total mass of the flux. The upper and lower limits of the ranges can be combined arbitrarily.

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

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

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

[0040] <Organic acid> The flux for water cleaning according to this embodiment contains a dimer acid and an organic sulfonic acid as organic acids.

[0041] <Dimer acid> The flux for water cleaning according to this embodiment contains a dimer acid as the organic acid. Dimer acids are dibasic acids obtained by dimerizing unsaturated fatty acids, and dibasic acids obtained by hydrogenating dibasic acids obtained by dimerizing unsaturated fatty acids. The unsaturated fatty acid preferably has 18 carbon atoms. Examples of the 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 formed by dimerization of one of the unsaturated fatty acids, or may be a dibasic acid formed by dimerization of two of the unsaturated fatty acids. The unsaturated fatty acids may contain isomers of the main component unsaturated fatty acids.

[0042] The dimer acids may be used singly or in combination of two or more. From the viewpoint of suppressing HiP, the dimer acid is preferably a dibasic acid formed by dimerization of 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 which is a hydrogenation product thereof, more preferably a dibasic acid formed by dimerization of oleic acid and linoleic acid, or a hydrogenated dibasic acid which is a hydrogenation product thereof, and even more preferably a hydrogenated dibasic acid which is a hydrogenation product of a dibasic acid formed by dimerization of oleic acid and linoleic acid. The dimer acid may contain, in addition to the dibasic acid that is the main component, a monobasic acid or a tribasic acid other than the dibasic acid.

[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, based on the total mass of the organic acids. The upper and lower limits of the above ranges can be combined in any desired manner.

[0044] The content of the dimer acid is preferably 1 to 30 mass %, more preferably 2 to 20 mass %, further preferably 5 to 15 mass %, and particularly preferably 5 to 10 mass %, relative to the total mass of the flux. The upper and lower limits of the ranges can be combined arbitrarily. When the content of the dimer acid is equal to or greater than the lower limit of the preferred range, the occurrence of HiP can be suppressed, and when the content is equal to or less than the upper limit of the preferred range, water washability is improved. When the content of the dimer acid is equal to or less than the upper limit of the preferred range, the generation of voids can be further suppressed.

[0045] <Organic sulfonic acid> The flux for water cleaning according to this embodiment contains an organic sulfonic acid as the organic acid. Examples of organic sulfonic acids include aliphatic sulfonic acids, aromatic sulfonic acids, etc. Examples of aliphatic sulfonic acids include alkanesulfonic acids, alkanolsulfonic acids, etc.

[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-naphthalenesulfonic acid, 2-naphthalenesulfonic acid, p-toluenesulfonic acid, xylenesulfonic acid, p-phenolsulfonic acid, cresolsulfonic acid, sulfosalicylic acid, nitrobenzenesulfonic acid, sulfobenzoic acid, and diphenylamine-4-sulfonic acid.

[0047] The organic sulfonic acids may be used alone or in combination of two or more. Among the above, the organic sulfonic acid preferably includes at least one selected from the group consisting of alkanesulfonic acids and aromatic sulfonic acids.

[0048] The content of the organic sulfonic acid is preferably 0.5 to 50 mass %, more preferably 1 to 30 mass %, further preferably 2 to 25 mass %, and particularly preferably 3 to 20 mass %, based on the total mass of the organic acid. The upper and lower limits of the above ranges can be combined in any desired manner.

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

[0050] The mass ratio of the dimer acid to the organic sulfonic acid can be adjusted appropriately, for example, within a range of dimer acid / organic sulfonic acid=0.5 to 80. From the viewpoint of HiP control, the mass ratio of dimer acid / organic sulfonic acid is preferably more than 1.0 and not more than 25, and more preferably more than 1.0 and not more than 20. When the mass ratio of the dimer acid to the organic sulfonic acid is within the above-mentioned preferred range, the generation of HiP can be suppressed.

[0051] Within the above-mentioned preferred range, when the mass ratio of the dimer acid to the organic sulfonic acid is more than 1.0 and not more than 20, the generation of voids can be further suppressed, and when the mass ratio of the dimer acid to the organic sulfonic acid is more than 1.0 and not more than 10, the generation of voids can be even more suppressed.

[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, based on the total mass of the organic acids. The upper and lower limits of the above ranges can be combined in any desired manner.

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

[0054] <Other organic acids> The flux for cleaning with water according to this embodiment may contain an organic acid other than the dimer acid and the organic sulfonic acid as the organic acid.

[0055] The flux for water cleaning according to this embodiment preferably further contains a dibasic acid as the 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, undecanedioic acid, dodecanedioic acid, eicosanedioic acid, terephthalic acid, dipicolinic acid, phthalic acid, isophthalic acid, and phenylsuccinic acid.

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

[0057] The dibasic acids may be used singly or in combination of two or more. The content of the dibasic acid is preferably from 0 to 50% by mass, more preferably from 3 to 45% by mass, and even more preferably from 5 to 40% by mass, based on the total mass of the organic acids. The content of the dibasic acid is preferably 0 to 5 mass %, more preferably 0.1 to 4 mass %, and even more preferably 0.2 to 3 mass %, relative to the total mass of the flux. The upper and lower limits of the ranges can be combined arbitrarily. When the content of the dibasic acid is within the above-mentioned preferred range, the occurrence of HiP can be suppressed.

[0058] When the dibasic acid contains a dibasic acid having four or less carbon atoms and the content thereof 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, more preferably 80 to 98% by mass, based on 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 mass %, more preferably 2 to 30 mass %, further preferably 5 to 20 mass %, and particularly preferably 5 to 15 mass %, based on the total mass of the flux. The upper and lower limits of the ranges can be combined arbitrarily.

[0060] Examples of organic acids other than the 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, and palmitoyl carboxylic acid. Examples include leic acid, oleic acid, elaidic acid, petroselinic acid, vaccenic acid, linoleic acid, linolenic acid, eleostearic acid, stearidonic acid, talic acid, ricinoleic acid, 12-hydroxystearic acid, 1,3-cyclohexanedicarboxylic acid, tris(2-carboxyethyl) isocyanurate, hiragonic acid, hydnocarpic acid, vernolic acid, sterculic 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-quinolinecarboxylic acid, and p-anisic acid.

[0061] The organic acids other than the dibasic acids may be used singly or in combination of two or more. The content of the organic acid other than the dibasic acid is preferably 0 to 25 mass %, more preferably 1 to 23 mass %, and even more preferably 2 to 20 mass %, based on the total mass of the organic acids. The content of the organic acid other than the dibasic acid is preferably 0 to 5 mass %, more preferably 0.1 to 4 mass %, and even more preferably 0.2 to 3 mass %, relative to the total mass of the flux. The upper and lower limits of the ranges can be combined arbitrarily.

[0062] The content of the organic acid is preferably 1.1 to 35 mass %, more preferably 3 to 25 mass %, further preferably 5 to 20 mass %, and particularly preferably 5 to 15 mass %, relative to the total mass of the flux. The upper and lower limits of the ranges can be combined arbitrarily.

[0063] <Solvent> The flux for water cleaning according to this embodiment contains a solvent. Examples of the solvent include glycol ether solvents, alcohol solvents, and ester 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), 2-methylpentane-2,4- ... Examples of suitable hydroxyhexane include 1,4-cyclohexanediol (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-decyne-4,7-diol, 2,2-bis(hydroxymethyl)-1,3-propanediol, and isobornylcyclohexanol. Examples of ester-based solvents include bis(2-ethylhexyl) sebacate.

[0066] The solvents may be used alone or in combination of two or more. From the viewpoint of suppressing voids and improving printability, it is more preferable that the solvent contains a solvent with a boiling point of 260°C or higher, and more preferable that the solvent contains 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), or tripropylene glycol n-butyl ether (boiling point 274°C).

[0067] The content of the solvent is preferably 10 to 70 mass %, more preferably 15 to 60 mass %, and even more preferably 15 to 50 mass %, relative to 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 mass %, more preferably 30 to 90 mass %, and more preferably 40 to 70 mass %, based on the total mass of the flux. The upper and lower limits of the ranges can be combined arbitrarily.

[0069] <Other ingredients> The flux for water cleaning according to the present embodiment may contain other components as needed, in addition to the water-soluble base agent selected from the nonionic surfactants, the organic acid, and the solvent. Examples of other components include other activators such as amines and halogen compounds, metal deactivators, silane coupling agents, antioxidants, colorants, and resin components.

[0070] Amine Examples of the amine include azoles, guanidines, alkylamine compounds, aminoalcohol 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. 1-cyanoethyl-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 isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazo 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-benzotriazolyl Examples of the benzotriazole include 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, and 5-phenyltetrazole.

[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 the amino alcohol compound include monoisopropanolamine, N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine, and N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine.

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

[0076] The diamine-terminated polyalkylene glycol is a compound in which both terminals of a polyalkylene glycol are aminated. Examples of diamine-terminated polyalkylene glycols include diamine-terminated polyethylene glycol, diamine-terminated polypropylene glycol, and diamine-terminated polyethylene glycol-polypropylene glycol (PEG-PPG) 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.

[0077] The aliphatic amine polyoxyalkylene adduct and the aromatic amine polyoxyalkylene adduct have a polyoxyalkylene group bonded to a nitrogen atom of an amine. Examples of the amine include ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, hexamethylenediamine, laurylamine, stearylamine, oleylamine, tallow amine, hardened tallow amine, tallow propyldiamine, diethylenetriamine, metaxylenediamine, paraxylenediamine, isophoronediamine, 1,10-decanediamine, 1,12-dodecanediamine, 4,4-diaminodicyclohexylmethane, tolylenediamine, butane-1,1,4,4-tetraamine, pyrimidine-2,4,5,6-tetraamine, phenylenediamine, and 4,4-diaminodiphenylmethane.

[0078] The amines may be used alone or in combination of two or more. Among the above, the amine may be It is preferable that the composition contains at least one selected from the group consisting of azoles, amino alcohol compounds, and amine polyoxyalkylene adducts, It is more preferable that the composition contains an azole and at least one selected from the group consisting of an amino alcohol compound and an amine polyoxyalkylene adduct, It is more preferable that the composition contains all of an azole, an amino alcohol compound, and an amine polyoxyalkylene adduct.

[0079] As the amine, it is preferable to use an imidazole compound among azoles, and alkyl group-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, and 1-cyanoethyl-2-ethyl-4-methylimidazole, as well as 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzoylimidazole, and the like. It is more preferable to use at least one selected from the group consisting of phenyl-substituted imidazole compounds such as 2-ethyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 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 selected from the group consisting of 2-ethylimidazole and 2-phenylimidazole.

[0080] As the amine, among amino alcohol compounds, 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, among amine polyoxyalkylene adducts, it is preferable to use at least one selected from the group consisting of diamine-terminated polyalkylene glycols and aliphatic amine polyoxyalkylene adducts, and among these, it is more preferable to use at least one selected from the group consisting of diamine-terminated polyethylene glycol-polypropylene glycol (PEG-PPG) copolymers and polyoxyethylene stearylamines.

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

[0083] The content of the amino alcohol compound is preferably from 0 to 95% by mass, more preferably from 20 to 75% by mass, and even more preferably from 35 to 55% by mass, based on the total mass of the amines. The content of the amino alcohol compound is preferably 0 to 30 mass %, more preferably 5 to 25 mass %, and even more preferably 7 to 23 mass %, relative to the total mass of the flux. The upper and lower limits of the ranges can be combined arbitrarily.

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

[0085] The content of the amine is preferably 15 to 40 mass %, more preferably 20 to 35 mass %, based on 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 mass % with respect 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 obtained by reacting an amine with hydrogen halide. The amines include aliphatic amines, azoles, guanidines, etc. The hydrogen halides include, for example, chlorine, bromine, and iodine hydrides. Examples of the aliphatic amine include ethylamine, diethylamine, triethylamine, ethylenediamine, etc. Examples of the guanidines and azoles include those described above for the amines.

[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-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, Diallylamine 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 fluoride 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.

[0090] Furthermore, examples of halogen compounds that can be used include salts obtained by reacting amines with tetrafluoroboric acid (HBF4) and complexes obtained by reacting amines with boron trifluoride (BF3). Examples of the complex 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 have been substituted with halogen atoms. Examples of the 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 the halogenated heterocyclic compound include compounds represented by the following general formula (1).

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

[0095] R 21In the above, the heterocyclic ring of the n-valent heterocyclic group may be a ring structure in which some of the carbon atoms constituting an aliphatic hydrocarbon or aromatic hydrocarbon ring are substituted with heteroatoms. Examples of the heteroatom in this heterocyclic ring include an oxygen atom, a sulfur atom, and a nitrogen atom. This heterocyclic ring is preferably a 3- to 10-membered ring, and more preferably a 5- to 7-membered ring. Examples of the heterocyclic ring include an isocyanurate ring. R 22 The halogenated aliphatic hydrocarbon group in R preferably has 1 to 10 carbon atoms, more preferably has 2 to 6 carbon atoms, and even more preferably has 3 to 5 carbon atoms. 22 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] Furthermore, examples of organic halogen compounds other than amine hydrohalides include halogenated carboxyl compounds such as 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. The halogen compounds may be used alone or in combination of two or more.

[0097] ≪Metal deactivator≫ Examples of metal deactivators include hindered phenol compounds and nitrogen compounds. The term "metal deactivator" as used herein refers to a compound that has the ability to prevent metals from deteriorating when in contact with certain compounds.

[0098] 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][ethylene bis(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'-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-biphenyl N-octylthio-6-(4-hydroxy-3,5-di-tert-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 of such an alkyl ester include N,N'-hexamethylenebis(3,5-di-tert-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 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] The melamine-based nitrogen compound may be any nitrogen compound having a melamine skeleton, such as melamine, melamine derivatives, etc. More specific examples include trisaminotriazine, alkylated trisaminotriazine, alkoxyalkylated trisaminotriazine, melamine, alkylated melamine, alkoxyalkylated melamine, N2-butylmelamine, N2,N2-diethylmelamine, N,N,N',N',N'',N''-hexakis(methoxymethyl)melamine, etc. The metal deactivators may be used alone or in combination of two or more.

[0104] <Resin component> From the viewpoint of improving water cleanability, the water-cleanable flux according to this embodiment preferably does not contain a resin component. In this specification, examples of the resin component include rosin and resins other than rosin.

[0105] As used herein, "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 content of abietic acid in the natural resin is, for example, 40% by mass or more and 80% by mass or less relative to the natural resin. In this specification, the term "main component" refers to a component that is contained in a compound in an amount of 40 mass % or more.

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

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

[0109] In the present invention, the term "chemically modified natural resin (rosin derivative)" includes the "natural resin" that has been subjected to one or more treatments selected from the group consisting of hydrogenation, dehydrogenation, neutralization, amidation, dimerization, oligomerization, 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 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, rosin ester, hydrogenated rosin ester, rosin soap, hydrogenated rosin soap, and acid-modified rosin soap.

[0111] Examples of rosin amines include dehydroabietylamine, dihydroabietylamine, etc. The rosin amine refers to a so-called disproportionated rosin amine.

[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 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.

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

[0114] The flux for water cleaning according to the present embodiment described above contains a water-soluble base agent selected from nonionic surfactants, an organic acid, and a solvent. The organic acid contains a dimer acid and an organic sulfonic acid, which provides excellent water cleaning properties and suppresses the generation of HiP. The flux for water cleaning according to the present embodiment contains a nonionic surfactant, which increases the affinity with water and improves the water cleanability of the flux residue. The water-cleanable flux according to this embodiment contains a dimer acid and an organic sulfonic acid as organic acids. Dimer acids are generally not widely used in water-cleanable fluxes because they have low affinity with water and thus reduce water cleanability. Furthermore, simply adding an organic sulfonic acid does not sufficiently improve the water cleanability of flux residues, and it is difficult to suppress HiP generation. However, surprisingly, we discovered that combining a dimer acid and an organic sulfonic acid as organic acids can suppress HiP generation while maintaining water cleanability, and we adopted this combination. The reason for this effect is unclear, but we speculate it may be due to the following reasons. In a solder paste using this flux, the viscosity of the molten solder paste increases, improving its ability to conform to the solder ball, thereby suppressing the occurrence of HiP. In addition, by including a dimer acid and an organic sulfonic acid as organic acids, the heat resistance of the activator in the flux is improved, thereby suppressing the occurrence of HiP.

[0115] The water-cleanable flux according to this embodiment further exhibits the effects of suppressing the generation of voids and providing excellent printability. The reason for this effect is believed to be that the inclusion of a dimer acid and an organic sulfonic acid as organic acids improves flux activity, making it easier to expel voids from the solder paste. Furthermore, the water-cleanable flux according to this embodiment contains a nonionic surfactant, which enhances the thixotropy of the solder paste using this flux, resulting in excellent printability.

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

[0117] The solder alloy powder may be composed of a powder of solder containing only Sn, or a powder of 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. The solder alloy powder may be composed of a powder of a solder alloy of Sn-Pb system or a Sn-Pb system to which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. have been added. The solder alloy powder is preferably a Pb-free solder. The solder alloy powder that can be used has a melting temperature of 150 to 250°C, for example.

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

[0119] Since the solder paste according to this embodiment contains the above-mentioned water-cleanable flux, This provides the effect of excellent water cleanability and suppressing the occurrence of HiP. The solder paste according to this embodiment also has the effect of suppressing the occurrence of voids and exhibiting excellent printability.

[0120] As another aspect, the present invention further includes the following embodiments.

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

[0122] [9] The flux for water cleaning according to any one of [1] to [6] and [8], further containing an amine.

[0123]

[10] The flux for water cleaning according to [9], wherein the amine comprises an azole and an amine-polyoxyalkylene adduct.

[0124]

[11] A water-cleanable solder paste containing the water-cleanable flux according to any one of [8] to

[10] and a solder alloy powder. [Example]

[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 to 16, Comparative Examples 1 to 7) Each flux in the examples and comparative examples was prepared with the composition shown in Tables 1 to 5. Example 1 is the same in Tables 1 to 4. In the tables, the content of each component is shown as a ratio (mass%) to the total mass of the flux (100 mass%). The raw materials used are listed below.

[0127] Water-soluble base: Nonionic surfactants (1) Behenyl alcohol EO adduct (BLAUNON® BE-30, manufactured by Aoki Oil & Fat Industries Co., Ltd.) (2) Polyethylene glycol (PEG-4000S, manufactured by Sanyo Chemical Industries, Ltd., average molecular weight: 3364) (3) Resorcinol-EO adduct (BARREL (registered trademark) 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 acids (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) Diamine-terminated 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 Nyukazai Co., Ltd.) (5) Polyoxyethylene stearylamine (Newcol (registered trademark) OD-420, Nippon Nyukazai Co., Ltd.)

[0131] <Preparation of solder paste> The flux of each example was mixed with the solder alloy powder shown below to prepare a solder paste. Each of the prepared solder pastes contained 10.5 mass % of flux and 89.5 mass % of solder alloy powder.

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

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

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

[0135] The prepared solder paste was printed on a printed circuit board using a 0.08 mm thick metal mask. After printing, a 1005Chip Capacitor (1005CC, dimensions 1.0 mm x 0.50 mm) was mounted on the printed circuit board and soldered by reflow at an oxygen concentration of 1000 ppm or less. Figure 1 shows the reflow profile, which was measured by increasing the temperature from 130°C to 220°C over 90 seconds, then holding the temperature at or above 220°C for 42 seconds, with a peak temperature of 242°C. After reflow, the substrate was placed in an ultrasonic cleaning tank filled with distilled water at 25-30°C and subjected to ultrasonic cleaning at an output of 40 kHz for 10 minutes. After that, the cleaned substrate was dried with an air blower. Next, the 1005CC component was removed, and the cleaning residue under the chip was observed using an SEM and an optical microscope. The number of cleaning residues remaining that connected (bridged) from an electrode under the same chip to an adjacent electrode was confirmed, and the ratio of the number of bridges to the total number of 128 chips was taken as the rate of cleaning defects (%). Cleaning defect rate (%) = Number of bridges (pieces) / Total number of chips 128 (pieces) x 100

[0136] Judgment criteria: A: 0% rate of defective cleaning B: Cleaning failure rate: over 0% and less than 5% C: Cleaning failure rate is 5% or more but less than 10% D: Cleaning failure rate: 10% to 20% E: Cleaning failure rate 20% or more Fluxes with evaluation results of A to C were judged as passing, and fluxes with evaluation results of D and E were judged as failing.

[0137] [HiP rating] The following printed circuit boards and BGA components were used. Printed circuit board: Material: FR-4, thickness: 0.8 mm, land dimensions: diameter: 0.24 mm 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 pre-processing: The BGA components were subjected to a heat treatment at a temperature of 85°C and a relative humidity of 85%RH for 24 hours, and then further to a heat treatment at 125°C for 1 hour.

[0138] The prepared solder paste was printed on a printed circuit board using a 0.08 mm thick metal mask. BGA components were mounted on the printed circuit board after printing, and reflow soldering was performed at an oxygen concentration of 1000 ppm or less. The reflow was performed under the same conditions as the reflow profile described in the "Evaluation of Water Cleanability" section above. After reflow, the BGA components were removed from the substrate, and the bonding state of the bumps was observed under an optical microscope to confirm the number of bonding defects (out of a total of 1,296 bumps).

[0139] Judgment criteria: A: Number of defective connections: 0 B: Number of defective connections is 1 or more but less than 5 C: Number of defective connections: 5 or more but less than 20 D: Number of defective connections: 20 or more but less than 30 E: 30 or more defective connections The fluxes with evaluation results A to C were judged as passing, and the fluxes with evaluation results D and E were judged as failing.

[0140] [Boyd's Evaluation] The following printed circuit boards and BGA components were used. Printed circuit board: Material: FR-4, thickness: 1.6 mm, land dimensions: diameter: 0.3 mm 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 on a printed circuit board using a 0.08 mm thick metal mask. BGA components were mounted on the printed circuit board after printing, and reflow soldering was performed at an oxygen concentration of 1000 ppm or less. Reflow was performed under the same conditions as the reflow profile in the "Evaluation of Water Cleanability" section above. In measuring the void area, if the 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 more were detected. After reflow, the bonded structure was irradiated with X-rays perpendicular to the substrate, and the area of ​​voids that occurred at the bonded portion between the bump and the land was measured by analyzing the transmitted X-rays. The measurement was performed using an XD7600NT Diamond X-ray inspection system (manufactured by Nordson DAGE). Next, the ratio of the void area to the bump area (void area ratio) was calculated, and the maximum value of the void area ratio (%) (maximum void area ratio) was confirmed among a total of 396 bumps.

[0142] Judgment criteria: A: Maximum void area ratio less than 5% B: Maximum void area ratio 5% or more and less than 10% C: Maximum void area ratio 10% or more and less than 15% D: Maximum void area ratio 15% or more and less than 20% E: Maximum void area ratio 20% or more The fluxes with evaluation results A to C were judged as passing, and the fluxes with evaluation results D and E were judged as failing.

[0143] [Printability evaluation] The following printed circuit boards were used: Printed circuit board: Material: FR-4, thickness: 1.6 mm, land dimensions: 0.25 mm x 0.50 mm, land spacing: 0.1 mm in the long side direction, 0.1 mm or 0.5 mm in the short side direction

[0144] The prepared solder paste was printed on a printed circuit board using a 0.08 mm thick metal mask. After printing, the board was observed under an optical microscope to check the rate (%) of solder paste bridging among a total of 128 lands.

[0145] Judgment criteria: A: Bridge occurrence rate 0% B: Bridge incidence rate: over 0% and less than 5% C: Bridge incidence rate is 5% or more but less than 10% D: Bridge incidence rate is 10% or more but less than 20% E: Bridge occurrence rate 20% or more The fluxes with evaluation results A to C were judged as passing, and the fluxes with evaluation results D and E were judged as failing.

[0146] [Table 1]

[0147] When the flux of Example 1 containing dimer acid and organic sulfonic acid as organic acids was used, the water cleanability was good and the occurrence of HiP was suppressed. When the flux of Comparative Example 3, which did not contain either a dimer acid or an organic sulfonic acid as the organic acid, was used, the occurrence of HiP increased, and the test was rated D.

[0148] When the flux of Comparative Example 2, which did not contain dimer acid as the organic acid but contained organic sulfonic acid, was used, the occurrence of HiP increased, and the test was rated D. When the flux of Comparative Example 4 was used in which oleic acid (a monocarboxylic acid having 18 carbon atoms) was used in place of the dimer acid of Example 1 in an amount equivalent to the dimer acid, the generation of HiP increased, resulting in an E rating.

[0149] When the flux of Comparative Example 1, which contained a dimer acid as an organic acid but did not contain an organic sulfonic acid, was used, the water cleanability decreased, and the flux was rated D. When the flux of Comparative Example 5, in which glutaric acid was used instead of the organic sulfonic acid of Example 1, was used, the occurrence of HiP increased, and the test was rated D.

[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 changed, were used, all of them had good water cleanability and suppressed the occurrence of HiP. Among the above examples, when 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, were used, the occurrence of HiP was further suppressed. Furthermore, among the above examples, when the fluxes of Examples 5, 4 and 1, in which the mass ratio of dimer acid to organic sulfonic acid was 0.5 to 5.3, were used, the generation of voids was further suppressed.

[0152] [Table 3]

[0153] When the flux of Example 1 was used, HiP and void generation were more suppressed than when the flux of Example 6, which contained glutaric acid instead of succinic acid in Example 1, was used. Furthermore, when the flux of Example 1 was used, void generation was more suppressed and printability was better than when 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, was used.

[0154] [Table 4]

[0155] [Table 5]

[0156] In Tables 4 and 5, when the fluxes of Examples 8 to 16 containing dimer acid and organic sulfonic acid as organic acids and variously changing other components were used, the water cleanability was good, the occurrence of HiP was suppressed, and furthermore, the occurrence of voids was suppressed, and the printability was good. When the flux of Comparative Example 6, which did not contain dimer acid as an organic acid, was used, the occurrence of HiP increased compared to when the fluxes of Examples 1 to 16 were used, and the result was an E rating. The flux of Comparative Example 7 is the flux described in Prior Art Document 1, but compared with the cases where the fluxes of Examples 1 to 16 were used, the occurrence of HiP increased, and the flux was rated E.

[0157] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Addition, omission, substitution, and other modifications of the configuration are possible within the scope of the spirit of the present invention. The present invention is not limited by the above description, but is limited only by the scope of the appended claims.

Claims

1. The composition contains a water-soluble base agent selected from nonionic surfactants, an organic acid, and a solvent, The organic acid includes a dimer acid and an organic sulfonic acid. the content of the dimer acid is 1 to 30 mass % based on the total mass of the flux for water cleaning; The flux for water cleaning, wherein the content of the organic sulfonic acid is 0.1 to 5 mass % based on the total mass of the flux for water cleaning.

2. The mass ratio of the dimer acid to the organic sulfonic acid is 2. The water-cleanable flux according to claim 1, wherein the ratio of the dimer acid to the organic sulfonic acid is greater than 1.0 and not greater than 20.

3. The organic acid further includes a dibasic acid having 4 or less carbon atoms, 2. The flux for water cleaning according to claim 1, wherein a content of the dibasic acid having 4 or less carbon atoms is more than 0 mass % and 5 mass % or less, based on a total mass of the flux for water cleaning.

4. 2. The water-cleanable flux according to claim 1, wherein the boiling point of the solvent is 260° C. or higher.

5. A water-cleanable solder paste comprising the water-cleanable flux according to any one of claims 1 to 4 and a solder alloy powder.

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