Flux and solder paste

Abstract

The present invention provides a soldering flux and solder paste, which can improve the wettability of electrodes subjected to various surface treatments such as Au plating, Cu-OSP treatment, and Sn plating. A soldering flux containing rosin, a solvent (S), a thixotropic agent, and an activator is used. The rosin contains rosin amine, and the S contains a first solvent (S1) having a boiling point of less than 250°C, and the content of S1 is greater than 50% by mass and less than 100% by mass relative to the total mass of the S.

Description

Technical Field

[0001] The present invention relates to a soldering flux and a solder paste. This application claims priority based on Japanese Patent Application No. 2021-096581 filed in Japan on June 9, 2021, and the contents thereof are incorporated herein by reference. Background Art

[0002] The flux used for soldering has the function of chemically removing the metal surface of the object to be soldered and the metal oxide present in the solder, and enabling the movement of metal elements at the boundary between the two. Therefore, by soldering with the flux, an intermetallic compound is formed between the two, thereby obtaining a strong connection. Such a flux generally contains a resin component, a solvent, an activator, a thixotropic agent, etc.

[0003] Solder paste is a composite material obtained by mixing solder alloy powder and flux. In soldering using solder paste, first, solder paste is printed on a substrate, components are mounted, and the substrate with components mounted is heated in a heating furnace called a reflow furnace.

[0004] Depending on the application, the electrodes of the electronic component mounting substrate may be subjected to various surface treatments such as Au plating, Cu-Organic Solderability Preservative (Cu-OSP) treatment, Sn plating, etc. It is desirable for the flux and solder paste to exhibit good wettability to the electrodes subjected to these various surface treatments.

[0005] On the other hand, a flux containing rosin amine is used (see Patent Documents 1 and 2).

[0006] For example, Patent Document 1 describes that a flux containing rosin amine exhibits a sufficient cleaning effect on various platings.

[0007] In addition, Patent Document 2 describes that a flux containing rosin amine hydrohalide salt exhibits excellent wettability to copper.

[0008] Prior art documents

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Publication No. 32-7056

[0011] Patent Document 2: Japanese Patent Publication No. 57-165198 Summary of the invention

[0012] Problems to be solved by the present invention

[0013] However, the fluxes described in Patent Documents 1 and 2 may not exhibit good wettability on electrodes subjected to various surface treatments after reflow.

[0014] Therefore, an object of the present invention is to provide a flux and a solder paste that improve wettability to electrodes subjected to various surface treatments.

[0015] Means of solving the problem

[0016] In order to solve the above-mentioned problems, the present invention adopts the following configuration.

[0017] [1] A soldering flux comprising rosin, a solvent (S), a thixotropic agent and an activator, wherein the rosin comprises rosin amine, the S comprises a first solvent (S1) having a boiling point of 250° C. or less, and the content of S1 is 50% by mass or more and 100% by mass or less relative to the total mass of the S.

[0018] [2] The soldering flux according to [1], wherein the boiling point of S1 is 150° C. or higher and 250° C. or lower.

[0019] [3] The soldering flux according to [1] or [2], wherein the S further contains a second solvent (S2) having a boiling point exceeding 250°C.

[0020] [4] The soldering flux according to any one of [1] to [3], wherein the rosin amine contains dehydrorosin amine.

[0021] [5] The soldering flux according to [4], wherein the rosin amine further contains dihydrorosin amine.

[0022] [6] A solder paste comprising a solder alloy powder and the flux described in any one of [1] to [5].

[0023] Effects of the Invention

[0024] According to the present invention, it is possible to provide a flux and a solder paste that improve wettability to electrodes subjected to various surface treatments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a photograph showing the wetting state of a substrate after reflow after printing solder paste on a substrate subjected to Au plating, Cu-OSP treatment, and Sn plating, and a diagram showing the criteria for determining the wetting. DETAILED DESCRIPTION

[0026] (Flux)

[0027] The soldering flux of the present embodiment contains rosin, a solvent (S), a thixotropic agent, and an activator.

[0028] <Rosin>

[0029] In the present invention, "rosin" includes natural resins containing abietic acid as a main component, mixtures of abietic acid and isomers thereof, and substances obtained by chemically modifying natural resins (sometimes referred to as rosin derivatives). The content of abietic acid in natural resins is, for example, 40% by mass or more and 80% by mass or less. Representative examples of isomers of abietic acid include neoabietic acid, palustric acid, and levopimaric acid. The structure of abietic acid is shown below.

[0030] In the present specification, the term "main component" refers to a component whose content in the compound is 40% by mass or more among the components constituting the compound.

[0031] [Chemical formula 1]

[0032]

[0033] In the present invention, "substances obtained by chemically modifying natural resins (rosin derivatives)" include substances obtained by subjecting the "natural resins" to one or more treatments selected from hydrogenation, dehydrogenation, neutralization, alkylene oxide addition, amidation, dimerization and polymerization, esterification, and Diels-Alder cycloaddition.

[0034] Rosin Amine

[0035] The rosin contained in the soldering flux of the present embodiment contains rosin amine as a rosin derivative.

[0036] Examples of the rosin amine include dehydroabietin amine and dihydroabietin amine.

[0037] The rosin amines may be used alone or in combination of two or more.

[0038] Rosin amine refers to so-called disproportionated rosin amine.

[0039] The structures of dehydroabietinamine and dihydroabietinamine are shown below.

[0040] [Chemical formula 2]

[0041]

[0042] The content of rosin amine in the soldering flux is greater than 0% by mass and less than 40% by mass, preferably greater than 2% by mass and less than 30% by mass, more preferably greater than 3% by mass and less than 20% by mass, further preferably greater than 3% by mass and less than 15% by mass, and particularly preferably greater than 5% by mass and less than 10% by mass, relative to the total amount of the soldering flux (100% by mass).

[0043] Other rosin

[0044] Rosin may contain other rosins in addition to rosin amine.

[0045] Examples of other rosins include raw material rosins such as gum rosin, wood rosin, and tall oil rosin, distilled rosin, and other rosin derivatives.

[0046] Examples of other rosin derivatives include hydrogenated rosin, polymerized rosin, polymerized hydrogenated rosin, disproportionated rosin, acid-modified rosin, acid-modified hydrogenated rosin, acid-modified disproportionated rosin, acid-anhydride-modified disproportionated rosin, phenol-modified rosin, and α,β-unsaturated carboxylic acid-modified products (acrylated rosin, maleated rosin, fumarated rosin, etc.), as well as purified products, hydrogenated products, and disproportionated products of the polymerized rosin, purified products, hydrogenated products, and disproportionated products of the α,β-unsaturated carboxylic acid-modified products, abietol, hydrogenated abietol, rosin ester, hydrogenated rosin ester, rosin soap, hydrogenated rosin soap, and acid-modified rosin soap.

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

[0048] As other rosin derivatives, among the above-mentioned rosins, it is preferable to use one or more selected from polymerized rosin and acid-modified hydrogenated rosin.

[0049] As the acid-modified hydrogenated rosin, acrylic acid-modified hydrogenated rosin is preferably used.

[0050] The total content of rosin in the flux is preferably 15% to 60% by mass, more preferably 20% to 50% by mass, and further preferably 23% to 45% by mass, relative to the total amount of the flux (100% by mass).

[0051] <Solvent (S)>

[0052] 《First solvent (S1)》

[0053] The solvent (S) contained in the flux of the present embodiment includes a first solvent (S1) having a boiling point of 250° C. or less. The boiling point of S1 is preferably 150° C. or more and 250° C. or less.

[0054] In this specification, the boiling point refers to the temperature of the liquid when the saturated vapor pressure of the liquid is equal to 1 atmospheric pressure. Solvents are exemplified below. The temperature in parentheses refers to the boiling point of the solvent.

[0055] Examples of S1 include water, glycol ether solvents having a boiling point of 250° C. or less, terpineols having a boiling point of 250° C. or less, alcohol solvents having a boiling point of 250° C. or less, and ester solvents having a boiling point of 250° C. or less.

[0056] As S1, glycol ether solvents having a boiling point of 150°C to 250°C, terpineols having a boiling point of 150°C to 250°C, alcohol solvents having a boiling point of 150°C to 250°C, and ester solvents having a boiling point of 150°C to 250°C are preferably used.

[0057] Examples of the glycol ether solvent having a boiling point of 150° C. to 250° C. include phenyl glycol (237° C.), butyl carbitol (230.6° C.), and tripropylene glycol monomethyl ether (243° C.).

[0058] Examples of terpineols having a boiling point of 150° C. to 250° C. include α-terpineol (218° C.), β-terpineol (210° C.), γ-terpineol (218° C.), and a terpineol mixture (i.e., a mixture containing α-terpineol as a main component and β-terpineol or γ-terpineol).

[0059] Examples of alcohol solvents having a boiling point of 250° C. or less include 1,2-butanediol (192° C.), 2,2-dimethyl-1,3-propanediol (210° C.), 2,5-dimethyl-2,5-hexanediol (215° C.), 2,5-dimethyl-3-hexyne-2,5-diol (206° C.), 2,3-dimethyl-2,3-butanediol (174° C.), hexanediol (197° C.), and 1-ethynyl-1-cyclohexanol (180° C.).

[0060] Examples of alcohol solvents having a boiling point of 150° C. to 250° C. include 1,2-butanediol (192° C.), 2,2-dimethyl-1,3-propanediol (210° C.), 2,5-dimethyl-2,5-hexanediol (215° C.), 2,5-dimethyl-3-hexyne-2,5-diol (206° C.), 2,3-dimethyl-2,3-butanediol (174° C.), hexanediol (197° C.), and 1-ethynyl-1-cyclohexanol (180° C.).

[0061] As S1, it is preferred to use one or more selected from phenyl glycol (237° C.), butyl carbitol (230.6° C.), hexylene glycol (197° C.), and α-terpineol (218° C.).

[0062] S1 may be used alone or in combination of two or more.

[0063] 《Second solvent (S2)》

[0064] The solvent (S) contained in the soldering flux of the present embodiment may contain a second solvent (S2) having a boiling point exceeding 250°C in addition to the first solvent (S1).

[0065] Examples of S2 include glycol ether solvents having a boiling point exceeding 250°C, alcohol solvents having a boiling point exceeding 250°C, and ester solvents having a boiling point exceeding 250°C.

[0066] Examples of glycol ether solvents having a boiling point exceeding 250°C include hexyl diethylene glycol (255°C), 2-ethylhexyl diethylene glycol (275°C), diethylene glycol dibutyl ether (256°C), triethylene glycol monobutyl ether (278°C), triethylene glycol butyl methyl ether (261°C), and tetraethylene glycol dimethyl ether (275°C).

[0067] Examples of alcohol solvents having a boiling point exceeding 250° C. include isobornylcyclohexanol (318° C.), 2,4-diethyl-1,5-pentanediol (338° C.), 2-ethyl-2-hydroxymethyl-1,3-propanediol (395° C.), 2,2′-oxybis(methylene)bis(2-ethyl-1,3-propanediol) (448° C.), 1,2,6-trihydroxyhexane (386° C.), 1,4-cyclohexanediol (293° C.), 1,4-cyclohexanedimethanol (283° C.), 2,4,7,9-tetramethyl-5-decyne-4,7-diol (255° C.), and 2,2-bis(hydroxymethyl)-1,3-propanediol (437° C.).

[0068] Examples of the ester solvent having a boiling point exceeding 250° C. include bis(2-ethylhexyl) sebacate (377° C.).

[0069] As S2, it is preferable to use one or more selected from the group consisting of hexyldiethylene glycol (255°C), 2-ethylhexyldiethylene glycol (275°C) and bis(2-ethylhexyl) sebacate (377°C).

[0070] S2 may be used alone or in combination of two or more.

[0071] The content of S1 contained in the flux of the present embodiment is 50 mass % or more and 100 mass % or less, preferably 60 mass % or more and 100 mass % or less, more preferably 70 mass % or more and 100 mass % or less, further preferably 80 mass % or more and 100 mass % or less, and particularly preferably 90 mass % or more and 100 mass % or less, relative to the total mass of S.

[0072] The total content of S contained in the soldering flux of the present embodiment is preferably 30 mass % or more and 80 mass % or less, and more preferably 40 mass % or more and 70 mass % or less, relative to the total amount of the soldering flux (100 mass %).

[0073] <Thixotropic agent>

[0074] Examples of the thixotropic agent include wax-based thixotropic agents, amide-based thixotropic agents, and sorbitol-based thixotropic agents.

[0075] The thixotropic agent may be used alone or in combination of two or more.

[0076] Examples of the wax-based thixotropic agent include ester compounds, and specific examples include hydrogenated castor oil.

[0077] The content of the wax-based thixotropic agent in the flux is preferably 2 mass % to 10 mass %, more preferably 3 mass % to 8 mass %, and further preferably 3 mass % to 6 mass %, relative to the total amount of the flux (100 mass %).

[0078] Examples of the amide-based thixotropic agent include monoamides, bisamides, and other polyamides.

[0079] Examples of the monoamide include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, saturated fatty acid amide, oleic acid amide, erucic acid amide, unsaturated fatty acid amide, p-toluamide, p-toluamide, aromatic amide, hexamethylene hydroxystearic acid amide, substituted amides, hydroxymethyl stearic acid amide, hydroxymethyl amide, and fatty acid ester amides.

[0080] Examples of the bisamides include methylene bisstearic acid amide, ethylene bislauric acid amide, ethylene bishydroxy fatty acid (fatty acid having carbon number of C6 to 24) amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, saturated fatty acid bisamides, methylene bisoleic acid amide, unsaturated fatty acid bisamides, meta-xylylene bisstearic acid amide, and aromatic bisamides.

[0081] Examples of other polyamides include saturated fatty acid polyamides, unsaturated fatty acid polyamides, aromatic polyamides, 1,2,3-propanetricarboxylic acid tris(2-methylcyclohexylamide), cyclic amide oligomers, and non-cyclic amide oligomers.

[0082] Examples of the cyclic amide oligomer include amide oligomers obtained by polycondensation of dicarboxylic acid and diamine to form a ring, amide oligomers obtained by polycondensation of tricarboxylic acid and diamine to form a ring, amide oligomers obtained by polycondensation of dicarboxylic acid and triamine to form a ring, amide oligomers obtained by polycondensation of tricarboxylic acid and triamine to form a ring, amide oligomers obtained by polycondensation of dicarboxylic acid, tricarboxylic acid and diamine to form a ring, amide oligomers obtained by polycondensation of dicarboxylic acid, tricarboxylic acid and triamine to form a ring, amide oligomers obtained by polycondensation of dicarboxylic acid, diamine and triamine to form a ring, amide oligomers obtained by polycondensation of tricarboxylic acid, diamine and triamine to form a ring, and amide oligomers obtained by polycondensation of dicarboxylic acid, tricarboxylic acid, diamine and triamine to form a ring.

[0083] In addition, the non-cyclic amide oligomers include: amide oligomers obtained by condensing monocarboxylic acids with diamines and / or triamines into non-cyclic forms, amide oligomers obtained by condensing dicarboxylic acids and / or tricarboxylic acids with monoamines into non-cyclic forms, and the like. In the case of amide oligomers containing monocarboxylic acids or monoamines, monocarboxylic acids and monoamines function as terminal molecules to form non-cyclic amide oligomers with reduced molecular weight. In addition, in the case of amide compounds obtained by condensing dicarboxylic acids and / or tricarboxylic acids with diamines and / or triamines into non-cyclic forms, the non-cyclic amide oligomers become non-cyclic high molecular amide polymers. In addition, non-cyclic amide oligomers also include amide oligomers obtained by condensing monocarboxylic acids with monoamines into non-cyclic forms.

[0084] The total content of the amide thixotropic agent in the flux is preferably 0 mass % to 30 mass % and more preferably 4 mass % to 20 mass % relative to the total amount (100 mass %) of the flux.

[0085] Examples of the sorbitol-based thixotropic agent include dibenzylidene-D-sorbitol, bis(4-methylbenzylidene)-D-sorbitol, (D-)sorbitol, monobenzylidene (-D-)sorbitol, and mono(4-methylbenzylidene)-(D-)sorbitol.

[0086] The content of the sorbitol-based thixotropic agent in the soldering flux is preferably 0 mass % to 5.0 mass % both inclusive, and more preferably 0 mass % to 3.5 mass % both inclusive, relative to the total amount (100 mass %) of the soldering flux.

[0087] The total content of the thixotropic agent contained in the flux of this embodiment is preferably 2 mass % to 20 mass % relative to the total amount of the flux (100 mass %), more preferably 3 mass % to 10 mass %, and further preferably 3 mass % to 6 mass %.

[0088] <Activator>

[0089] Examples of the activator include organic acids, halogen-based activators, and amines.

[0090] The soldering flux of the present embodiment preferably contains one or more selected from the group consisting of an organic acid, a halogen-based activator, and an amine.

[0091] Organic Acids:

[0092] Examples of the organic acid include glutaric acid, adipic acid, azelaic acid, eicosanedioic acid, citric acid, glycolic acid, succinic acid, salicylic acid, diglycolic acid, pyridine dicarboxylic acid, dibutylaniline diglycolic acid, suberic acid, sebacic acid, thioglycolic acid, dimercaptoacetic acid, terephthalic acid, dodecanedioic acid, p-hydroxyphenylacetic acid, picolinic acid, phenylsuccinic acid, phthalic acid, fumaric acid, maleic acid, malonic acid, lauric acid, benzoic acid, tartaric acid, tris(2-carboxyethyl)isocyanurate, glycine, 1,3-cyclohexanedicarboxylic acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butyric acid, 2,3-dihydroxybenzoic acid, 2,4-diethylglutaric acid, 2-quinolinecarboxylic acid, 3-hydroxybenzoic acid, propionic acid, malic acid, p-anisic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, palmitic acid, pimelic acid, dimer acid, trimer acid, hydrogenated dimer acid which is a hydrogenated product of dimer acid, hydrogenated trimer acid which is a hydrogenated product of trimer acid, and the like.

[0093] The organic acid may be used alone or in combination of two or more.

[0094] As the organic acid, dicarboxylic acid is preferably used.

[0095] As dicarboxylic acid, glutaric acid is preferably used.

[0096] The total content of the organic acid in the soldering flux is preferably 1 mass % or more and 10 mass % or less, and more preferably 2 mass % or more and 6 mass % or less, relative to the total amount (100 mass %) of the soldering flux.

[0097] Halogen-based activators:

[0098] Examples of the halogen-based activating agent include halogenated aliphatic compounds and amine hydrohalides.

[0099] The halogen-based activators may be used alone or in combination of two or more.

[0100] Examples of the halogenated aliphatic compound 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, 2,3-dibromo-1,4-butanediol, and trans-2,3-dibromo-2-butene-1,4-diol.

[0101] Amine hydrohalides are compounds obtained by reacting amines with hydrogen halides. Examples of the amines include ethylamine, diethylamine, triethylamine, ethylenediamine, 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, and 1-o-tolylguanidine. Examples of the hydrogen halides include hydrides of chlorine, bromine, and iodine.

[0102] The soldering flux of the present embodiment preferably contains a halogen-based activator.

[0103] As the halogen-based activator, an amine hydrohalide is preferably used.

[0104] As the amine hydrohalide salt, it is preferred to use a hydrohalide salt of 1,3-diphenylguanidine.

[0105] As the hydrohalide salt of 1,3-diphenylguanidine, 1,3-diphenylguanidine·HBr is preferably used.

[0106] The total content of the halogen-based activators in the flux is preferably 0 mass % to 5 mass %, preferably 0.2 mass % to 3 mass %, and more preferably 0.4 mass % to 2 mass %, relative to the total amount of the flux (100 mass %).

[0107] amine:

[0108] Examples of the amine include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, diphenylguanidine, 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole trimellitate, 1-cyanoethyl-2-phenylimidazole trimellitate, 2,4-diamino-6-[2'- 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, 2,4-Diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazole chloride, 2-methylimidazoline, 2-phenylimidazoline, 2,4- Diamino-6-vinyl-s-triazine, 2,4-diamino-4,6-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, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-pentylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole , 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol], 6-(2-benzotriazolyl)-4-tert-octyl-6'-tert-butyl-4'-methyl-2,2'-methylenebisphenol, 1,2,3-benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, carboxybenzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, 2,2'-[[(methyl-1H-benzotriazol-1-yl)methyl]imino]bisethanol, 1-(1',2'-dicarboxyethyl)benzotriazole, 1-(2,3-dicarboxypropyl)benzotriazole, 1-[(2-ethylhexylamino)methyl]benzotriazole, 2,6-Bis[(1H-benzotriazol-1-yl]methyl]-4-methylphenol, 5-methylbenzotriazole, 5-phenyltetrazolyl, etc.

[0109] The amines may be used alone or in combination of two or more.

[0110] As the amine, it is preferred to use one or more selected from 2-ethylimidazole and diphenylguanidine.

[0111] The content of amine in the flux is preferably 0 mass % to 20 mass %, more preferably 0 mass % to 10 mass %, and further preferably 3 mass % to 10 mass %, relative to the total amount of the flux (100 mass %).

[0112] <Other ingredients>

[0113] Furthermore, the soldering flux of the present embodiment may contain other components in addition to the rosin, the solvent, the thixotropic agent, and the activator.

[0114] As other components, a surfactant, a silane coupling agent, and a coloring agent are mentioned, for example.

[0115] Examples of the surfactant include nonionic surfactants and weakly cationic surfactants.

[0116] Examples of the nonionic surfactant include polyethylene glycol, polyethylene glycol-polypropylene glycol copolymers, aliphatic alcohol polyoxyethylene adducts, aromatic alcohol polyoxyethylene adducts, and polyhydric alcohol polyoxyethylene adducts.

[0117] Examples of the weak cationic surfactant include terminal diamine polyethylene glycol, terminal diamine polyethylene glycol-polypropylene glycol copolymer, aliphatic amine polyoxyethylene adducts, aromatic amine polyoxyethylene adducts, and polyamine polyoxyethylene adducts.

[0118] Examples of surfactants other than the surfactants exemplified above include polyoxyethylene acetylene glycols, polyoxyethylene glycerol ethers, polyoxyethylene alkyl ethers, polyoxyethylene esters, polyoxyethylene alkylamines, and polyoxyethylene alkylamides.

[0119] In addition, in the soldering flux of the present embodiment, an antioxidant may be used for the purpose of suppressing oxidation of the solder alloy powder. As the antioxidant, a hindered phenol-based antioxidant may be used.

[0120] The soldering flux of the present embodiment exhibits sufficient wettability on electrodes subjected to Au plating, Cu-OSP treatment, or Sn plating.

[0121] Compared with Au-plated electrodes, Cu-OSP-plated electrodes and Sn-plated electrodes are difficult to wet because their surfaces are easily oxidized. In addition, among these three electrodes, Sn-plated electrodes are the most difficult to wet because their surfaces are most easily oxidized.

[0122] The flux of this embodiment contains rosin amine and a first solvent (S1) having a boiling point of 250°C or less, and the content of S1 is 50% by mass or more relative to the total mass of S. This increases the amount of solvent volatilization during reflow soldering, increases the concentration of rosin and activator, and as a result, it is estimated that the wettability of the flux is improved.

[0123] (Solder Paste)

[0124] The solder paste of the present embodiment contains solder alloy powder and the above-mentioned flux.

[0125] The solder alloy powder can be composed of powder of solder of Sn alone, or powder of solder alloy of Sn-Ag system, Sn-Cu system, Sn-Ag-Cu system, Sn-Bi system, Sn-In system, etc., or powder of solder alloy to which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. are added.

[0126] The solder alloy powder may be composed of powder of a solder alloy of Sn-Pb system or Sn-Pb system to which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. are added.

[0127] The solder alloy powder is preferably a solder that does not contain Pb.

[0128] Flux content:

[0129] In the solder paste, the content of the flux is preferably 5 to 30% by mass, more preferably 5 to 15% by mass, based on the total mass of the solder paste.

[0130] The solder paste of the present embodiment exhibits sufficient wettability on electrodes subjected to various surface treatments.

[0131] The solder paste of this embodiment contains rosin amine and a first solvent (S1) having a boiling point of 250°C or less, and the content of S1 is 50% by mass or more relative to the total mass of S, thereby increasing the volatilization amount of the solvent during reflow soldering, and increasing the concentration of rosin and activator. As a result, it is estimated that the wettability of the flux is improved.

[0132] The solder paste of the present embodiment exhibits sufficient wettability to any of the Au-plated electrode, the Cu-OSP-plated electrode, and the Sn-plated electrode.

[0133] The specific configuration of the embodiment of the present invention is not limited to the embodiment of the present disclosure, and changes, substitutions, etc. may be made without departing from the gist of the present disclosure.

[0134] Example

[0135] Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to the following examples.

[0136] <Preparation of flux>

[0137] (Examples 1 to 12, Comparative Examples 1 to 6)

[0138] The fluxes of Examples and Comparative Examples were prepared according to the compositions shown in Tables 1 and 2.

[0139] rosin:

[0140] Acrylic acid modified hydrogenated rosin

[0141] Polymerized rosin

[0142] Rosin Amine

[0143] A first solvent (S1) having a boiling point of 250°C or less:

[0144] Phenyl glycol (boiling point 237°C)

[0145] Butyl carbitol (boiling point 230.6℃)

[0146] α-Terpineol (boiling point 218℃)

[0147] Hexanediol (boiling point 197°C)

[0148] A second solvent (S2) having a boiling point exceeding 250°C:

[0149] Hexyldiethylene glycol (boiling point 255°C)

[0150] 2-Ethylhexyldiethylene glycol (boiling point 275°C)

[0151] Bis(2-ethylhexyl) sebacate (boiling point 377°C)

[0152] In addition, the composition ratios in Tables 1 and 2 are based on the mass % when the total mass of the flux is 100 mass %, and blank columns represent 0 mass %.

[0153] <Preparation of Solder Paste>

[0154] The flux of each example was mixed with the following solder alloy powder to prepare a solder paste. The prepared solder pastes all contained 10.5% by mass of the flux and 89.5% by mass of the solder alloy powder.

[0155] The solder alloy powder in the solder paste is a powder composed of a solder alloy containing 3 mass % of Ag, 0.5 mass % of Cu, and the remainder of Sn.

[0156] The solder alloy powder has a size (particle size distribution) that satisfies symbol 6 in the classification of powder size in JIS Z 3284-1:2014 (Table 2).

[0157] <Evaluation of Wettability>

[0158] (1) Verification method

[0159] Three types of substrates were prepared, namely, substrates subjected to Au plating, Cu-OSP treatment, and Sn plating.

[0160] The pad size was set to 8 mm×8 mm, the mask thickness was set to 80 μm, and the prepared solder paste was printed on each substrate.

[0161] Reflow soldering is performed on the printed board.

[0162] The reflow conditions are as follows: heating to 150°C at 2°C / sec, heating at 150°C to 180°C for 80 seconds, heating to 180°C to 240°C at 2°C / sec, and maintaining at 220°C or above for 40 seconds.

[0163] The reflow process was performed in a N2 atmosphere with an oxygen concentration of 80 to 150 ppm.

[0164] The surface condition of each substrate after reflow was evaluated based on the following criteria.

[0165] (2) Criteria for determination

[0166] A: The solder wets evenly to the printed surface.

[0167] B: Dehumidification occurred at the printed periphery.

[0168] C: Dewetting occurred on more than half of the printed surface.

[0169] The following are photos showing the wetting state of the substrates after reflow soldering and the criteria for determining the wetting after printing solder paste on substrates plated with Au, Cu-OSP, and Sn, respectively. Figure 1 . Figure 1 From the left, the substrates were plated with Au, Cu-OSP, and Sn. From the top, the evaluation of the wettability is A, B, and C.

[0170] The results of Examples 1 to 12 and Comparative Examples 1 to 6 are shown in Tables 1 and 2.

[0171] [Table 1]

[0172]

[0173] [Table 2]

[0174]

[0175] The soldering flux of Example 1 contains acrylic acid-modified hydrogenated rosin, polymerized rosin, and 3% by mass of rosin amine as rosin, contains α-terpineol as the first solvent (S1), contains glutaric acid and diphenylguanidine·HBr as the activator, and contains hydrogenated castor oil as the thixotropic agent, and the content of S1 is 100% by mass relative to the total mass of the solvent.

[0176] The soldering flux of Example 1 has a wettability of A for Au-plated substrates, a wettability of B for Cu-OSP-treated glass epoxy substrates, and a wettability of B for Sn-plated substrates.

[0177] The soldering flux of Example 2 has wettability of A on Au-plated substrates, A on Cu-OSP-treated glass epoxy substrates, and A on Sn-plated substrates even when the content of rosin amine is increased to 5 mass %.

[0178] The soldering flux of Example 3 has wettability A on the Au-plated substrate, A on the Cu-OSP-treated glass epoxy substrate, and A on the Sn-plated substrate even when the content of rosin amine is increased to 10 mass %.

[0179] The soldering flux of Example 4 has wettability of A on Au-plated substrates, A on Cu-OSP-treated glass epoxy substrates, and B on Sn-plated substrates even when the content of rosin amine is increased to 15 mass %.

[0180] The soldering flux of Example 5 has wettability of A for Au-plated substrate, A for Cu-OSP-treated glass epoxy substrate, and A for Sn-plated substrate even when the content of hydrogenated castor oil is reduced to 3 mass % and the contents of acrylic acid-modified hydrogenated rosin and polymerized rosin are increased to 20 %, respectively.

[0181] The soldering flux of Example 6, even if containing phenyl glycol as S1, had wettability of A on the Au-plated substrate, A on the Cu-OSP-treated glass epoxy substrate, and A on the Sn-plated substrate.

[0182] The soldering flux of Example 7, even though containing butyl carbitol as S1, had wettability of A on the Au-plated substrate, A on the Cu-OSP-treated glass epoxy substrate, and A on the Sn-plated substrate.

[0183] The soldering flux of Example 8, even if containing hexylene glycol as S1, had A wettability on the Au-plated substrate, A wettability on the Cu-OSP-treated glass epoxy substrate, and A wettability on the Sn-plated substrate.

[0184] The soldering flux of Example 9, which contains diphenylguanidine and 2-ethylimidazole instead of diphenylguanidine·HBr, has wettability A on Au-plated substrates, A on Cu-OSP-treated glass epoxy substrates, and A on Sn-plated substrates.

[0185] The soldering flux of Example 10 has a wettability of B for Au-plated substrates, B for Cu-OSP-treated glass epoxy substrates, and B for Sn-plated substrates, even if it contains hexylene glycol as S1 and hexyldiethylene glycol as the second solvent (S2) and the content of S1 is reduced to 62.8 mass % relative to the total mass of the solvent.

[0186] The soldering flux of Example 11 has wettability of B on the Au-plated substrate, B on the Cu-OSP-treated glass epoxy substrate, and B on the Sn-plated substrate even when the content of S1 is reduced to 50 mass % relative to the total mass of S.

[0187] The soldering flux of Example 12 has a wettability of B on an Au-plated substrate, B on a Cu-OSP-treated glass epoxy substrate, and B on a Sn-plated substrate even if it contains α-terpineol as S1 and bis(2-ethylhexyl) sebacate as S2 and the content of S1 is reduced to 61% by mass relative to the total mass of the solvent.

[0188] The soldering flux of Example 1 containing rosin amine has a wettability of A on the Au-plated substrate, a wettability of B on the Cu-OSP-treated glass epoxy substrate, and a wettability of B on the Sn-plated substrate.

[0189] On the other hand, the soldering flux of Comparative Example 1 which does not contain rosin amine has a wettability of C on the Au-plated substrate, the Cu-OSP-treated glass epoxy substrate, and the Sn-plated substrate.

[0190] The soldering flux of Example 2, in which the content of S1 was 50 mass % or more and 100 mass % or less based on the total mass of S, had wettability of A on the Au-plated substrate, the Cu-OSP-treated glass epoxy substrate, and the Sn-plated substrate.

[0191] On the other hand, the soldering fluxes of Comparative Examples 2 and 3, in which the content of S1 was less than 50 mass % based on the total mass of S, had wettability of C on the Au-plated substrate, the Cu-OSP-treated glass epoxy substrate, and the Sn-plated substrate.

[0192] The soldering fluxes of Examples 10 to 12, in which the content of S1 was 50 mass % or more and 100 mass % or less based on the total mass of S, had wettability of B on the Au-plated substrate, the Cu-OSP-treated glass epoxy substrate, and the Sn-plated substrate.

[0193] On the other hand, the soldering flux of Comparative Example 4, in which the content of S1 was less than 50 mass % based on the total mass of S, had wettability of C on the Au-plated substrate, the Cu-OSP-treated glass epoxy substrate, and the Sn-plated substrate.

[0194] The soldering flux of Example 4, in which the content of S1 is 50 mass % or more and 100 mass % or less relative to the total mass of S, has wettability A on Au-plated substrates, wettability A on Cu-OSP-treated glass epoxy substrates, and wettability B on Sn-plated substrates.

[0195] On the other hand, in the soldering flux of Comparative Example 5 in which the content of S1 was less than 50 mass % based on the total mass of S, the wettability of the Au-plated substrate, the Cu-OSP-treated glass epoxy substrate, and the Sn-plated substrate was C.

[0196] The soldering fluxes of Examples 10 to 12 in which the content of S1 was 50 mass % or more and 100 mass % or less based on the total mass of S, showed wetting of B on the Au-plated substrate, the Cu-OSP-treated glass epoxy substrate, and the Sn-plated substrate.

[0197] On the other hand, the flux of Comparative Example 6 in which the content of S1 is less than 50 mass % relative to the total mass of the solvent has a wettability of B to the Au-plated substrate and the Cu-OSP-treated glass epoxy substrate, but has a wettability of C to the Sn-plated substrate.

[0198] The flux and solder paste of Examples 1 to 12 of the present invention contain rosin amine and S1 with a boiling point of less than 250°C, and the content of S1 is more than 50% by mass relative to the total mass of S, thereby increasing the volatilization amount of the solvent during reflow soldering and increasing the concentration of rosin and activator. As a result, the wettability to Au-plated substrates, Cu-OSP-treated glass epoxy substrates and Sn-plated substrates can be sufficient.

[0199] In addition, in the flux of Examples 2 to 3 and 5 to 9 of the present invention, the content of rosin amine is 5 mass % or more and 10 mass % or less relative to the total mass of the flux, and the content of S1 is 70 mass % or more and 100 mass % or less relative to the total mass of S, which can achieve excellent wettability to Au-plated substrates, Cu-OSP-treated glass epoxy substrates and Sn-plated substrates.

[0200] Industrial Applicability

[0201] The present invention provides a soldering flux and a solder paste which improve wettability to electrodes subjected to various surface treatments such as Au plating, Cu-OSP treatment, and Sn plating. The soldering flux and the solder paste are suitable for joining electrodes subjected to various surface treatments.

Claims

1. A soldering flux comprising rosin, a solvent (S), a thixotropic agent and a halogen-based activator, The rosin contains rosin amine, The solvent (S) is composed of a first solvent (S1) having a boiling point of 150° C. or higher and 237° C. or lower, The content of the rosin amine is 5 mass % or more and 10 mass % or less relative to the total amount of the soldering flux.

2. The soldering flux according to claim 1, wherein The rosin amine contains dehydrorosin amine.

3. The soldering flux according to claim 2, wherein: The rosin amine further contains dihydrorosin amine.

4. A solder paste comprising a solder alloy powder and the flux according to any one of claims 1 to 3.

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