Flux and solder paste

Abstract

To provide a water-soluble flux and solder paste that can suppress generation of a void and suppress heating droop.SOLUTION: A water-soluble flux includes sugar alcohol, an amine polyoxyalkylene adduct and a solvent (S).SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to flux and solder paste. [Background technology]

[0002] The fixing of components to a circuit board and the electrical connection of components to the circuit board are generally performed by soldering. Soldering involves the use of flux, solder powder, and solder paste, which is a mixture of flux and solder powder. Flux chemically removes metal oxides from the metal surfaces of the objects to be soldered and from the solder itself, allowing for the movement of metal elements at the boundary between them. Therefore, using flux during soldering allows for the formation of intermetallic compounds between the two, resulting in a strong bond.

[0003] In soldering using solder paste, the solder paste is first printed onto the circuit board, then the components are mounted, and the circuit board with the components mounted is heated in a heating oven called a reflow oven. This melts the solder powder contained in the solder paste, and the components are soldered to the circuit board.

[0004] The flux used in soldering generally contains resin components, solvents, activators, thixotropes, etc. 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 for cleaning after soldering, which can cause problems in terms of safety and the environment. Therefore, there has been a demand for water-soluble flux that can be easily cleaned with water after soldering.

[0005] Patent Document 1 describes a flux containing an organic acid polyglycerol ester, a thixotropic agent, and a solvent having a specific SP value. According to the flux described in Patent Document 1, the cleanability of soldering with water after soldering is improved. [Prior art documents]

Patent Document

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In a reflow furnace, after preheating, main heating for melting solder alloy powder is performed. The solder paste printed on the substrate softens during preheating and may cause dripping. Dripping can cause mounting defects such as solder balls and solder bridges.

[0008] Also, in the reflow process, moisture contained in the flux, gasified flux, etc. may form voids in the joint. Voids reduce the reliability of the components mounted by soldering.

[0009] On the other hand, it is difficult to suppress the occurrence of dripping and voids in the solder paste using the flux described in Patent Document 1. Therefore, an object of the present invention is to provide a water-soluble flux and a solder paste that can suppress the generation of voids and suppress dripping.

Means for Solving the Problems

[0010] The present invention includes the following aspects. A first aspect of the present invention is a water-soluble flux containing a sugar alcohol, an amine polyoxyalkylene adduct, and a solvent (S).

[0011] In the water-soluble flux according to the first aspect, it is preferable that the sugar alcohol contains a compound represented by the following general formula (1).

[0012]

Chemical formula

[0013] In the water-soluble flux according to the first aspect, the amine polyoxyalkylene adduct preferably contains one or more selected from the group consisting of a terminal diamine polyalkylene glycol and an aliphatic amine polyoxyalkylene adduct.

[0014] The water-soluble flux according to the first aspect preferably further contains an organic acid.

[0015] In the water-soluble flux according to the first aspect, the organic acid preferably includes a hydroxycarboxylic acid.

[0016] In the water-soluble flux according to the first aspect, the solvent (S) preferably contains a first solvent (S1) having a boiling point exceeding 250°C.

[0017] In the water-soluble flux according to the first aspect, the solvent (S) preferably further contains a second solvent (S2) having a boiling point of 250°C or lower.

[0018] The water-soluble flux according to the first aspect preferably further contains an amino alcohol.

[0019] A second aspect of the present invention is a solder paste containing solder alloy powder and the water-soluble flux according to the first aspect. [Advantages of the Invention]

[0020] According to the present invention, it is possible to provide a water-soluble flux and a solder paste that can suppress the generation of voids and suppress sagging during heating. [Embodiments for Carrying Out the Invention]

[0021] (Flux) The water-soluble flux according to this embodiment contains a sugar alcohol, an amine polyoxyalkylene adduct, and a solvent (S).

[0022] In this specification, water-soluble flux means flux whose flux residue can be removed by washing with water. Hereafter, water-soluble flux may be simply referred to as flux.

[0023] <Sugar alcohols> The water-soluble flux according to this embodiment contains a sugar alcohol. A sugar alcohol is a type of sugar produced by the reduction of the carbonyl group of an aldose or ketose. The sugar alcohol may be a compound having a chain-like structure or a compound having a cyclic structure.

[0024] The sugar alcohol preferably contains a compound represented by the following general formula (1).

[0025] [ka] [In equation (1), n ​​represents a positive integer.]

[0026] In formula (1), n ​​is preferably 1 to 10, more preferably 1 to 6, and even more preferably 1 to 4.

[0027] Examples of compounds represented by the above general formula (1) include glycerol, erythritol, treitol, ribitol, arabinitol, xylitol, allitol, sorbitol, mannitol, iditol, galactitol, talitol, and the like.

[0028] The compound represented by the above general formula (1) is preferably one or more selected from the group consisting of erythritol, xylitol, mannitol, and sorbitol.

[0029] The sugar alcohol content in the flux may be 0.1% by mass or more and 30% by mass or less, with a preference of 0.25% by mass or more and 20% by mass or less, based on the total amount of the flux (100% by mass). If the sugar alcohol content is above the lower limit, the occurrence of voids becomes easier to suppress. If the sugar alcohol content is below the upper limit, the decrease in flux tackiness becomes easier to suppress.

[0030] <Amine polyoxyalkylene adducts> The water-soluble flux according to this embodiment contains an amine polyoxyalkylene adduct. In this specification, an amine polyoxyalkylene adduct means an amine to which an alkylene oxide has been added.

[0031] Examples of amine polyoxyalkylene adducts include terminal diamine polyalkylene glycols, aliphatic amine polyoxyalkylene adducts, aromatic amine polyoxyalkylene adducts, and polyvalent amine polyoxyalkylene adducts. Examples of alkylene oxides attached to amine polyoxyalkylene adducts include ethylene oxide, propylene oxide, and butylene oxide.

[0032] 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 copolymers. 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.

[0033] Aliphatic amine polyoxyalkylene adducts, aromatic amine polyoxyalkylene adducts, and polyvalent amine polyoxyalkylene adducts are formed in which a polyoxyalkylene group is bonded to the nitrogen atom of an amine. Examples of such amines include ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, hexamethylenediamine, diethylenetriamine, laurylamine, stearylamine, oleylamine, tallowamine, hydrogenated tallowamine, tallowpropyldiamine, metaxyldiamine, tolylenediamine, paraxyldiamine, phenylenediamine, isophoronediamine, 1,10-decanediamine, 1,12-dodecanediamine, 4,4-diaminodicyclohexylmethane, 4,4-diaminodiphenylmethane, butane-1,1,4,4-tetraamine, pyrimidine-2,4,5,6-tetraamine, and the like.

[0034] The amine polyoxyalkylene adduct may be used individually or as a mixture of two or more types. As the amine polyoxyalkylene adduct, one or more selected from the group consisting of terminal diamine polyalkylene glycols and aliphatic amine polyoxyalkylene adducts are preferred.

[0035] The content of the amine polyoxyalkylene adduct in the flux may be 10% by mass or more and 70% by mass or less, preferably 15% by mass or more and 60% by mass or less, and more preferably 20% by mass or more and 50% by mass or less, based on the total amount of the flux (100% by mass). When the amine polyoxyalkylene adduct content is above the aforementioned lower limit, it becomes easier to suppress sagging during heating. In addition, it becomes easier to increase the viscosity of the flux. By keeping the amine polyoxyalkylene adduct content below the aforementioned upper limit, it becomes possible to adjust the viscosity of the solder paste to a suitable level.

[0036] The mixing ratio of the amine polyoxyalkylene adduct to the sugar alcohol is preferably 1 to 250, and more preferably 1.8 to 170, expressed as the mass ratio of amine polyoxyalkylene adduct to sugar alcohol, i.e., the ratio of the total amount of amine polyoxyalkylene adduct to the total amount of sugar alcohol. When the mass ratio is within the above range, the generation of voids is more easily suppressed, and the tendency for sagging during heating is also more easily suppressed.

[0037] <Solvent (S)>

[0038] Examples of solvents include glycol ether-based solvents, alcohol-based solvents, ester-based solvents, and terpineols.

[0039] In this specification, the boiling point means the temperature of a liquid at which its saturated vapor pressure is equal to 1 atmosphere.

[0040] Examples of glycol ether solvents with a boiling point exceeding 250°C include 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), and tetraethylene glycol dimethyl ether (boiling point 275°C).

[0041] Examples of glycol ether solvents with a boiling point of 250°C or lower include phenyl glycol (boiling point 237°C), butyl carbitol (boiling point 231°C), hexylene glycol (boiling point 197°C), and tripropylene glycol monomethyl ether (boiling point 243°C).

[0042] Examples of alcohol-based solvents with a boiling point exceeding 250°C include 2,4,7,9-tetramethyl-5-decine-4,7-diol, 2,2-bis(hydroxymethyl)-1,3-propanediol, and isobornylcyclohexanol.

[0043] Examples of alcohol-based solvents with a boiling point of 250°C or lower 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), 2,5-dimethyl-2,5-hexanediol (boiling point 215°C), 2,5-dimethyl-3-hexyn-2,5-diol (boiling point 206°C), 2,3-dimethyl-2,3-butanediol (boiling point 174°C), 2-methylpentane-2,4-diol (boiling point 197°C), and 1-ethynyl-1-cyclohexanol (boiling point 180°C).

[0044] Examples of ester-based solvents with a boiling point exceeding 250°C include bis(2-ethylhexyl) sebacate (boiling point 435°C).

[0045] Examples of terpineols with a boiling point below 250°C include α-terpineol (boiling point 217°C).

[0046] S1 may be used alone or in a mixture of two or more types. The water-soluble flux according to this embodiment preferably contains a first solvent (S1) having a boiling point above 250°C. Examples of S1 include glycol ether solvents, alcohol solvents, and ester solvents having a boiling point above 250°C. The water-soluble flux according to this embodiment preferably contains a second solvent (S2) having a boiling point of 250°C or lower, in addition to the first solvent (S1). The lower limit of the boiling point of S2 is not particularly limited, but it is preferably 50°C or higher, more preferably 100°C or higher, and even more preferably 150°C or higher.

[0047] Examples of S2 include glycol ether solvents with a boiling point of 250°C or less, alcohol solvents with a boiling point of 250°C or less, ester solvents with a boiling point of 250°C or less, and terpineols with a boiling point of 250°C or less.

[0048] S2 may be used alone or in a mixture of two or more types. When the flux of this embodiment contains S2, the S2 content is preferably more than 0% by mass and 50% by mass or less, and more preferably 20% by mass or more and 50% by mass or less, relative to the total mass of S. If the S2 content is above the lower limit, void formation is more easily suppressed. If the S2 content is below the upper limit, the increase in viscosity of the solder paste due to solvent evaporation and the deterioration of the solder paste are more easily suppressed.

[0049] The total amount of S contained in the flux according to this embodiment is the remainder determined according to the other components, and is preferably 20% to 70% by mass, more preferably 25% to 60% by mass, and even more preferably 30% to 50% by mass, based on the total amount of the flux (100% by mass).

[0050] <Other ingredients> In addition to sugar alcohols, amine polyoxyalkylene adducts, and solvents, the flux according to this embodiment may contain other components as needed. Other components include organic acids, amines (excluding amine polyoxyalkylene adducts), halogen compounds and other activators, surfactants, metal deactivators, antioxidants, silane coupling agents, and colorants.

[0051] ≪Activators≫ Examples of activators include organic acids, amines (excluding amine polyoxyalkylene adducts), and halogen compounds.

[0052] [Organic acid] Examples of organic acids include carboxylic acids and organic sulfonic acids. Examples of carboxylic acids include aliphatic carboxylic acids and aromatic carboxylic acids. Examples of aliphatic carboxylic acids include aliphatic monocarboxylic acids and aliphatic dicarboxylic acids. Examples of aliphatic monocarboxylic acids include caproic acid, enanthic acid, caprylic acid, pelargonic acid, isoperargonic acid, capric acid, caproleic acid, lauric acid (dodecanoic acid), undecanoic acid, lindelic acid, tridecanoic acid, myristoleic acid, pentadecanoic acid, isopalmitic acid, palmitoleic acid, hyragonic acid, hydrocarpic acid, margaric acid, isostearic acid, elaidic acid, petroseric acid, molocinic acid, eleostearic acid, taliric acid, vaccenic acid, liminoleic acid, vernolic acid, sterkric acid, nonadecanoic acid, eicosanoic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, myristic acid, and others. Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanediic acid, eicosanedioic acid, tartaric acid, and 2,4-diethylglutaric acid. Examples of aromatic carboxylic acids include salicylic acid, dibutylaniline diglycolic acid, terephthalic acid, parahydroxyphenylacetic acid, phenylsuccinic acid, phthalic acid, benzoic acid, 2,3-dihydroxybenzoic acid, 2-quinoline carboxylic acid, 3-hydroxybenzoic acid, and p-anisic acid. Other examples of carboxylic acids include tris(2-carboxyethyl) isocyanurate and 1,3-cyclohexanedicarboxylic acid.

[0053] Furthermore, examples of carboxylic acids include compounds represented by the following general formula (c1).

[0054] R 11 -COOH ···(c1) [In the formula, R 11 R represents a chain hydrocarbon group having 2 to 15 carbon atoms, an alicyclic hydrocarbon group having 3 to 15 carbon atoms, or an aromatic group. However, R11 It has a hydroxyl group.

[0055] R 11 The chain-like hydrocarbon group in the above-mentioned material may be either linear or branched. The chain-like hydrocarbon group and the alicyclic hydrocarbon group may be saturated hydrocarbon groups or unsaturated hydrocarbon groups, but it is preferable that they be saturated hydrocarbon groups.

[0056] The number of carbon atoms in the chain-like hydrocarbon group is preferably 2 to 12, more preferably 3 to 9, particularly preferably 3 to 7, and most preferably 3 to 5.

[0057] Examples of the aforementioned chain-like hydrocarbon groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, sec-pentyl group, tert-pentyl group, neopentyl group, n-hexyl group, isohexyl group, sec-hexyl group, tert-hexyl group, and neohexyl group.

[0058] The number of carbon atoms in the alicyclic hydrocarbon group is preferably 3 to 12, more preferably 4 to 12, and even more preferably 4 to 8.

[0059] Examples of the alicyclic hydrocarbon group include cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclononyl group, cyclodecyl group, and cycloundecyl group.

[0060] R 11 The aromatic group in this context is a group having at least one aromatic ring, and examples include aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene; aromatic heterocycles in which some of the carbon atoms constituting the aromatic hydrocarbon ring are replaced by heteroatoms; and fused rings formed by the fusion of an aromatic hydrocarbon ring and an aromatic heterocycle. R 11If the aromatic group in has substituents, examples of substituents include hydrocarbon groups having 1 to 20 carbon atoms, aromatic hydrocarbon groups, carboxyl groups, hydroxyl groups, amino groups, halogen atoms, etc., with carboxyl groups or hydroxyl groups being preferred.

[0061] Examples of organic acids represented by the above general formula (c1) include hydroxycarboxylic acids. Examples of hydroxycarboxylic acids include 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butanoic acid, citric acid, isocitric acid, malic acid, tartaric acid, etc., with 2,2-bis(hydroxymethyl)propionic acid being preferred.

[0062] Furthermore, examples of carboxylic acids include dimer acids, trimer acids, hydrogenated dimer acids (which are hydrogenated products of dimer acids), and hydrogenated trimer acids (which are hydrogenated products of trimer acids). Dimer acids and trimer acids include, for example, dimer acid which is a reaction product of oleic acid and linoleic acid, trimer acid which is a reaction product of oleic acid and linoleic acid, dimer acid which is a reaction product of acrylic acid, trimer acid which is a reaction product of acrylic acid, dimer acid which is a reaction product of methacrylic acid, trimer acid which is a reaction product of methacrylic acid, dimer acid which is a reaction product of acrylic acid and methacrylic acid, trimer acid which is a reaction product of acrylic acid and methacrylic acid, dimer acid which is a reaction product of oleic acid, trimer acid which is a reaction product of linoleic acid, dimer acid which is a reaction product of linoleic acid, trimer acid which is a reaction product of linoleic acid, dimer acid which is a reaction product of linolenic acid, trimer acid which is a reaction product of acrylic acid and oleic acid, dimer acid which is a reaction product of acrylic acid and linoleic acid, acrylic Examples include trimer acid, a reaction product of acid and linoleic acid; dimer acid, a reaction product of acrylic acid and linolenic acid; trimer acid, a reaction product of acrylic acid and linolenic acid; dimer acid, a reaction product of methacrylic acid and oleic acid; trimer acid, a reaction product of methacrylic acid and linoleic acid; dimer acid, a reaction product of methacrylic acid and linoleic acid; dimer acid, a reaction product of methacrylic acid and linoleic acid; trimer acid, a reaction product of methacrylic acid and linolenic acid; dimer acid, a reaction product of oleic acid and linolenic acid; dimer acid, a reaction product of linoleic acid and linolenic acid; dimer acid, a reaction product of linoleic acid and linolenic acid; hydrogenated dimer acid, a hydrogenated product of each of the above-mentioned dimer acids; and hydrogenated trimer acid, a hydrogenated product of each of the above-mentioned trimer acids. For example, dimer acid, a reaction product of oleic acid and linoleic acid, is a dimer with 36 carbon atoms. Trimer acid, another reaction product of oleic acid and linoleic acid, is a trimer with 54 carbon atoms.

[0063] Furthermore, examples of carboxylic acids include compounds represented by the following general formula (a1).

[0064] [ka] [In formula (a1), R 1 , R 2 , R 3 and R 4 each independently represent a hydrocarbon group, a hydroxy group, a halogen atom or a hydrogen atom.]

[0065] R 1 , R 2 , R 3 and R 4 Examples of the hydrocarbon group in include a linear hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, an alicyclic hydrocarbon group having 3 to 20 carbon atoms which may have a substituent, an amino group, a hydroxy group, a carboxy group, etc. The linear hydrocarbon group may be linear or branched. The linear hydrocarbon group is a saturated hydrocarbon group or an unsaturated hydrocarbon group, and is preferably a saturated hydrocarbon group. The alicyclic hydrocarbon group may be a polycyclic group or a monocyclic group. As the monocyclic alicyclic hydrocarbon group, a group obtained by removing one or more hydrogen atoms from a monocycloalkane is preferable. As the polycyclic alicyclic hydrocarbon group, a group obtained by removing one or more hydrogen atoms from a polycycloalkane is preferable. R 1 , R 2 , R 3 and R 4 Examples of the substituent that the hydrocarbon group in

[0066] may have include an amino group, a hydroxy group, a carboxy group, an acyl group, an alkoxy group, a carbonyl group, a halogen atom, etc. The hydrocarbon group is preferably a linear hydrocarbon group having 1 to 5 carbon atoms which may have a substituent or a carboxy group. Examples of the linear hydrocarbon group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a neopentyl group, etc. The hydrocarbon group is preferably a carboxy group. Examples of compounds represented by the above general formula (a1) include picolinic acid, dipicolinic acid, and 3-hydroxypicolinic acid.

[0067] The compound represented by the above general formula (a1) is preferably picolinic acid. In the above general formula (a1), R 1 , R 2 , R 3 and R 4 It is a compound in which the atom is a hydrogen atom.

[0068] 3-Hydroxypicolinic acid is R in the above general formula (a1). 1 is a hydroxyl group, and R 2 , R 3 and R 4 It is a compound in which the atom is a hydrogen atom.

[0069] Examples of organic sulfonic acids include aliphatic sulfonic acids and aromatic sulfonic acids. Examples of aliphatic sulfonic acids include alkanesulfonic acids and alkanolsulfonic acids.

[0070] 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.

[0071] Organic acids may be used individually or in mixtures of two or more types. The organic acid preferably contains one or more selected from the group consisting of carboxylic acids and organic sulfonic acids, and more preferably contains a compound represented by the above general formula (c1).

[0072] When the flux according to this embodiment contains an organic acid, the organic acid content is preferably 2% by mass or more and 20% by mass or less, more preferably 4% by mass or more and 15% by mass or less, and even more preferably 6% by mass or more and 10% by mass or less, based on the total amount of the flux (100% by mass).

[0073] [amine] Examples of amines other than amine polyoxyalkylene adducts include amino alcohols, azoles, guanidines, and alkylamine compounds.

[0074] Examples of amino alcohols include N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, 1-amino-2-propanol, bis(2-hydroxypropyl)amine, and tris(2-hydroxypropyl)amine.

[0075] 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.

[0076] 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.

[0077] Examples of alkylamine compounds include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, and stearylamine.

[0078] Amines may be used individually or in mixtures of two or more. As the amine, an amino alcohol is preferred. When the flux according to this embodiment contains amino alcohol, the amino alcohol content is preferably 2% by mass or more and 20% by mass or less, and more preferably 4% by mass or more and 15% by mass or less, relative to the total amount of the flux (100% by mass). By having an amino alcohol content above the lower limit mentioned above, the formation of voids becomes easier to suppress. By having an amino alcohol content below the upper limit mentioned above, it becomes possible to adjust the viscosity of the solder paste to a suitable level.

[0079] [Halogen compounds] Examples of halogen compounds include amine hydrohalides and organic halogen compounds other than amine hydrohalides. Amine hydrohalides are compounds formed by reacting an amine with a hydrogen halide. Examples of amines used here include those mentioned above in the section on [amines].

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] Examples of heterocyclic halogenated compounds include compounds represented by the following general formula (h1).

[0085] R 21 -(R 22 ) n (h1) [In the formula, R 21 R represents an n-valent heterocyclic group. 22 This represents a halogenated aliphatic hydrocarbon group.

[0086] 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 this heterocyclic ring 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.

[0087] 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.

[0088] ≪Base Material≫ Examples of base materials include nonionic surfactants. Examples of nonionic surfactants include polyoxyalkylene adducts. Examples of alkylene oxides derived from polyoxyalkylene adducts include ethylene oxide, propylene oxide, and butylene oxide. Examples of polyoxyalkylene adducts include polyethylene glycol, polypropylene glycol, ethylene oxide-resorcinol copolymer, polyoxyalkylene acetylene glycols, polyoxyalkylene glyceryl ether, polyoxyalkylene alkyl ether, polyoxyalkylene ester, and polyoxyalkylene alkylamide. Alternatively, nonionic surfactants include polyoxyalkylene adducts of alcohols. Examples of such alcohols include aliphatic alcohols, aromatic alcohols, and polyhydric alcohols.

[0089] The base material may be used alone or in a mixture of two or more types. As the base material, nonionic surfactants are preferred, polyoxyalkylene adducts are more preferred, and one or more selected from the group consisting of polyethylene glycol and polyoxyalkylene adducts of alcohols are even more preferred. The weight-average molecular weight of polyethylene glycol is preferably 1000 to 5000, and more preferably 1500 to 4000.

[0090] When the flux according to this embodiment contains a base material, the base material content is preferably more than 0% by mass and 30% by mass or less, and more preferably 5% by mass or more and 20% by mass or less, relative to the total amount of flux (100% by mass). If the base material content is above the lower limit, it becomes easier to suppress the occurrence of voids. If the base material content is below the upper limit, it becomes easier to suppress the decrease in flux adhesion.

[0091] ≪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.

[0092] 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], 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-bis-(n-oc (Tylthio)-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'-hexamethylenebis Examples include (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, N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxamide, and compounds represented by the following chemical formulas.

[0093] [ka] (In the formula, Z is an alkylene group that may be substituted. 81 and R 82 Each of these is independently an alkyl group, aralkyl group, aryl group, heteroaryl group, cycloalkyl group, or heterocycloalkyl group, which may be substituted. 83 and R 84 These are, independently, alkyl groups that may be substituted.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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. Metal deactivators may be used individually or in combination of two or more types.

[0099] The water-soluble flux according to this embodiment preferably does not contain resin components. The absence of resin components makes it easier to wash the flux residue with water. In this specification, examples of resin components include rosin, resins other than rosin, and the like.

[0100] 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). 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 rosin, maleated rosin, fumarated 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 ester, hydrogenated rosin ester, rosin soap, hydrogenated rosin soap, acid-modified rosin soap, and the like.

[0101] 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.

[0102] 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 water-soluble flux because it does not contain at least one resin component selected from the group consisting of rosin and thermosetting resins.

[0103] According to the flux of the embodiment described above, by combining a sugar alcohol and an amine polyoxyalkylene adduct, it is possible to suppress the generation of voids and suppress heat sagging.

[0104] (Solder paste) The solder paste of this embodiment contains solder alloy powder and the flux described above.

[0105] As the solder alloy, solder alloys of known compositions can be used. The solder alloy may consist of elemental Sn solder, or Sn-Ag, Sn-Cu, Sn-Ag-Cu, Sn-Bi, Sn-In, etc., or solder alloys to which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. are added. The solder alloy may consist of a Sn-Pb system, or a solder alloy 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 is preferably a Pb-free solder alloy, and more preferably a solder alloy containing Sn and Bi.

[0106] Flux content: The flux content 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.

[0107] According to the solder paste of the embodiment described above, by combining a sugar alcohol and an amine polyoxyalkylene adduct, it is possible to suppress melting during heating. Furthermore, it is hypothesized that the moisture contained in the solder paste, as well as the moisture generated when metal oxides present on the metal surface of the objects being joined are removed, hydrates with the sugar alcohols contained in the flux, thereby reducing the occurrence of voids. According to the flux of the above embodiment, void formation can be suppressed even in solder alloys containing easily oxidized Sn and Bi. [Examples]

[0108] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0109] <Preparation of flux> (Examples 1-18, Comparative Examples 1-4) Fluxes for the examples and comparative examples were prepared with the compositions shown in Tables 1-4.

[0110] Sugar alcohols: Erythritol, xylitol, mannitol, sorbitol

[0111] Amine polyoxyalkylene adducts: Terminal-diamine polyethylene glycol-polypropylene glycol copolymer, polyoxyethylene stearylamine Amino alcohol: N,N,N',N'-Tetrakis(2-hydroxypropyl)ethylenediamine

[0112] Azoles: 2-ethylimidazole, 2-ethyl-4-methylimidazole Organic acids: Glutaric acid, 2,2-bis(hydroxymethyl)propionic acid, p-toluenesulfonic acid

[0113] Solvents: Diethylene glycol mono-2-ethylhexyl ether (boiling point 272°C), α-terpineol (boiling point 217°C) Base material: Polyethylene glycol, polyoxyethylene behenyl ether

[0114] PEG4000S (manufactured by Sanyo Chemical Industries, Ltd.) was used as the polyethylene glycol. The weight-average molecular weight of PEG4000S is approximately 3500 in PEG equivalent molecular weight.

[0115] Polyoxyethylene behenyl ether is a compound represented by the following formula (d1).

[0116] [ka] [In equation (d1), n1 is between 25 and 35.]

[0117] <Preparation of Solder Paste> Solder pastes were prepared by mixing the fluxes from Examples 1-18 and Comparative Examples 1-4 with the solder alloy powder (1) described below. In all of the prepared solder pastes, the flux was 10% by mass and the solder alloy powder was 90% by mass. Solder pastes were prepared by mixing the flux from Example 1 and Comparative Example 1 with the solder alloy powder (2) described below. The prepared solder pastes contained 12% flux by mass and 88% solder alloy powder by mass.

[0118] The solder alloy powder (1) is a powder consisting of a solder alloy with 58% by mass of Bi and the remainder being Sn. This solder alloy has a melting point of 139°C. The size of the solder alloy powder (1) is a size (particle size distribution) that satisfies symbol 5 in the powder size classification (Table 2) of JIS Z 3284-1:2014.

[0119] Solder alloy powder (2) 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 size of solder alloy powder (2) is the same as that of solder alloy powder (1).

[0120] The evaluation methods described in the <Evaluation> section below were used to evaluate the void formation rate, heat sagging, and tacking. The results of these evaluations are shown in Tables 1-5.

[0121] ≪Evaluation of Void Occurrence Rate≫ (1) Evaluation method Solder paste was printed onto a copper plate (30mm x 30mm x 0.3mm) using a metal mask (with an opening size of φ0.5mm and a mask thickness of 0.1mm). Next, the printed copper plate was reflow soldered using a high-temperature observation device in a nitrogen atmosphere (oxygen concentration of 500 ppm or less). The reflow profile was obtained with a heating rate of 2°C / second, held at 140°C or higher for 40 seconds, and peaking at 190°C. Void area was measured by irradiating the soldered joint with X-rays from the vertical direction of the substrate after soldering and analyzing the transmitted X-rays. An XD7600NT Diamond X-ray inspection system (Nordson DAGE) was used for the measurement. The instrument conditions during measurement were set to 120kV, 3.0W, 32Avg, and a field of view of 11mm. In measuring void area, if X-rays 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. Next, the ratio of the total void area to the total area of ​​the joint to be measured was calculated and expressed as the void occurrence rate (%).

[0122] (2) Judgment criteria A: The void occurrence rate was 2.5% or less. B: The void occurrence rate was between 2.5% and 3.5%. C: was over 3.5%. Fluxes that received an A or B rating were deemed to have passed, while those that received a C rating were deemed to have failed.

[0123] ≪Evaluation of heat-induced sagging suppression ability≫ (1) Evaluation method Solder paste was printed onto a copper plate (30mm x 30mm x 0.3mm) using a metal mask (with an opening size of φ0.5mm and a mask thickness of 0.1mm). A copper plate printed with solder paste was placed on a hot plate and heated at 100°C for 1 minute. The diameter of the solder paste was measured before and after heating. Next, the elongation rate of the solder paste diameter after heating was calculated relative to the solder paste diameter before heating (100%).

[0124] (2) Judgment criteria A: The elongation rate of the solder paste diameter after heating was 5% or less. B: The elongation rate of the solder paste diameter after heating was more than 5%. Flux that received an A rating was deemed to pass, while flux that received a B rating was deemed to fail.

[0125] ≪Evaluation of tucking≫ (1) Evaluation method The tackiness of the flux was evaluated according to the evaluation method described in JIS Z 3284-3(2014) 4.5. A tacking tester TACII (manufactured by Lesca Corporation) was used as the measuring device. Using a metal mask, solder paste was printed onto an alumina plate to create four printed patterns with a diameter of 6.5 mm and a thickness of 0.2 mm. Next, the printed patterns were placed under the probe of a tacking test machine, and the centers of the patterns were aligned with the centers of the probe. The probe was then lowered into the paste at a speed of 2.0 mm / s and a constant pressure of 0.05 ± 0.005 N was applied. Within 0.2 seconds after applying pressure, the probe was pulled up at a speed of 10 mm / s. For each of the four printed patterns, the force required to remove the probe was measured, and the maximum force was defined as the adhesive force.

[0126] (2) Judgment criteria A: The adhesive strength was 70 gf or higher (i.e., 0.69 N or higher). B: The adhesive strength was less than 70 gf (i.e., less than 0.69 N). Here, 1[gf] = 9.8 × 10 -3 [N] is the case.

[0127] [Table 1]

[0128] [Table 2]

[0129] [Table 3]

[0130] [Table 4]

[0131] [Table 5]

[0132] The fluxes in Comparative Examples 1 to 4, which are outside the scope of the present invention, either received a void generation rate of C or a heating sagging suppression ability of B when using solder alloy powder (1). In contrast, the fluxes of Examples 1 to 18, which are within the scope of the present invention, were evaluated as A or B in terms of void generation rate when using solder alloy powder (1), and were evaluated as A in terms of heat sagging suppression ability.

[0133] As shown in Tables 4-5, the flux of Comparative Example 1 received a void generation rate evaluation of C when using solder alloy powder (1) and a void generation rate evaluation of B when using solder alloy powder (2). Solder alloy powder (1) composed of Sn and Bi is more easily oxidized than solder alloy powder (2) composed of Sn, Ag, and Cu. Therefore, it is presumed that it is more difficult to reduce the void generation rate of solder alloy powder (1) than of solder alloy powder (2). The flux of the present invention can reduce the void generation rate even when using solder alloy powder (1). [Industrial applicability]

[0134] According to the present invention, it is possible to provide a water-soluble flux and solder paste that can suppress the generation of voids and suppress heat sagging. The water-soluble flux of the present invention can be suitably used for soldering using Sn-Bi solder alloy, which is easily oxidized.

Claims

1. It contains a sugar alcohol, an amine polyoxyalkylene adduct, and a solvent (S). The solvent (S) includes a solvent (S1) having a boiling point greater than 250°C. The amine polyoxyalkylene adduct comprises one or more selected from the group consisting of terminal diamine polyalkylene glycols and aliphatic amine polyoxyalkylene adducts. The sugar alcohol content is 0.1% by mass or more and 30% by mass or less, relative to the total amount of flux (100% by mass). The content of the amine polyoxyalkylene adduct is 10% by mass or more and 70% by mass or less, relative to the total amount of flux (100% by mass). A water-soluble flux in which the solvent (S) content is 20% by mass or more and 70% by mass or less, based on the total amount of flux (100% by mass).

2. The water-soluble flux according to claim 1, wherein the sugar alcohol comprises a compound represented by the following general formula (1). 【Chemistry 1】 [In equation (1), n ​​represents a positive integer.]

3. Furthermore, the water-soluble flux according to claim 1 or 2, further containing an organic acid.

4. The water-soluble flux according to claim 3, wherein the organic acid comprises a hydroxycarboxylic acid.

5. The water-soluble flux according to any one of claims 1 to 4, wherein the solvent (S) further comprises a solvent (S2) having a boiling point of 250°C or less.

6. Furthermore, the water-soluble flux according to any one of claims 1 to 5, further containing an amino alcohol.

7. Solder paste comprising solder alloy powder and a water-soluble flux according to any one of claims 1 to 6.

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