Flux and solder paste

Abstract

Provided are a flux and a solder paste having good reflow properties and flux residue cleaning properties, wherein changes in viscosity over time upon storage at 30°C are suppressed and coloring of flux residue can be suppressed.　A flux, containing rosin, a thixotropic agent, an activator and a solvent, is employed as such a flux. The rosin includes at least one selected from the group consisting of acid-modified rosin, hydrogenated rosin, and acid-modified hydrogenated rosin, and the thixotropic agent includes a compound represented by general formula (1).　In general formula (1), R11 and R12 each independently represent a C1-C3 hydrocarbon group that may have a substituent, or a single bond. R21 and R22 each independently represent a C7-C29 hydrocarbon group that may have a substituent. R13 is a substituent. n represents an integer of 0-4.

Description

[Technical Field]

[0001] The present invention relates to a flux and a solder paste. This application claims priority based on Japanese Patent Application No. 2021-104992, filed on June 24, 2021, the contents of which are incorporated herein by reference. [Background technology]

[0002] Fluxes used in soldering chemically remove metal oxides present on the metal surfaces of the objects being soldered and in the solder, allowing the migration of metal elements at the interface between the two. Therefore, soldering using a flux forms an intermetallic compound between the two, resulting in a strong bond. Such fluxes generally contain resin components, solvents, activators, thixotropic agents, etc.

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

[0004] After reflow, even if cleaning is performed, the remaining flux (flux residue) may cause leakage current, migration, etc. To address this, flux that has good cleaning properties for flux residue is used. Here, "good cleaning properties for flux residue" means that excess flux can be easily cleaned and removed using a cleaning agent. For example, a flux containing hardened castor oil, which has a relatively low melting point, as a thixotropic agent has been proposed (Patent Document 1). Furthermore, in the examples of Patent Document 2, a flux containing hardened castor oil and hydrogenated rosin is described. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-249577 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-117745 Summary of the Invention [Problem to be solved by the invention]

[0006] The solder paste described in Patent Document 1, which uses a flux containing hardened castor oil and polymerized rosin, may result in colored flux residue. Furthermore, the solder paste described in Patent Document 2, which uses a flux containing hardened castor oil and hydrogenated rosin, may experience an increase in viscosity over time when stored at 30°C.

[0007] Therefore, an object of the present invention is to provide a flux and a solder paste that have good reflow properties and good cleaning properties for flux residue, that are inhibited from changing in viscosity over time when stored at 30°C, and that are capable of inhibiting discoloration of flux residue. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present inventors have conducted extensive research into the components of the flux. The inventors first investigated the resin component. The inventors have found that a solder paste using a flux containing polymerized rosin in addition to hardened castor oil may result in colored flux residue. Furthermore, the inventors have found that a solder paste using a flux containing rosin ester in addition to hardened castor oil may not have sufficient reflowability.

[0009] Therefore, the inventors prepared a solder paste using a flux containing hydrogenated rosin or acid-modified rosin in addition to hardened castor oil. However, the inventors discovered that although this solder paste has sufficient reflow properties and sufficiently suppresses coloration of flux residue, it has the problem of a significant increase in viscosity when stored at 30°C.

[0010] The inventors have found that even when hydrogenated rosin or acid-modified rosin is used, by combining it with a compound (specific thixotropic agent) represented by the following general formula (1), the reflow property and cleaning property of flux residue are good, the change in viscosity over time when stored at 30°C is suppressed, and the coloring of flux residue can be suppressed, and thus the present invention has been completed.

[0011] The present invention includes the following aspects. [1] Contains rosin, a thixotropic agent, an activator, and a solvent, The rosin includes one or more specific rosins selected from the group consisting of acid-modified rosin, hydrogenated rosin, and acid-modified hydrogenated rosin, The thixotropic agent is a flux containing a compound represented by the following general formula (1):

[0012] [ka] [In the formula, R 11 and R 12 R each independently represents a hydrocarbon group having 1 to 3 carbon atoms which may have a substituent, or a single bond. 21 and R 22 R each independently represents a hydrocarbon group having 7 to 29 carbon atoms which may have a substituent. 13 is a substituent, and n represents an integer of 0 to 4.

[0013] [2] The flux according to [1], wherein the content of the compound represented by the general formula (1) is 0.5 mass % or more and 10 mass % or less with respect to the total mass of the flux.

[0014] [3] The thixotropic agent further includes an ester-based thixotropic agent, The flux according to [1] or [2], wherein the content of the ester-based thixotropic agent is more than 0 mass % and 4 mass % or less with respect to the total mass of the flux.

[0015] [4] The flux according to any one of [1] to [3], wherein the content of the activator is 1 mass % or more and 20 mass % or less with respect to the total mass of the flux. [5] The flux according to any one of [1] to [4], wherein the content of the specific rosin is 10% by mass or more and 70% by mass or less with respect to the total mass of the flux. [6] The flux according to any one of [1] to [5], wherein the activator includes at least one selected from the group consisting of organic acid-based activators and halogen-based activators.

[0016] [7] A solder paste containing a solder alloy powder and the flux according to any one of [1] to [6] above. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a flux and a solder paste that have good reflow properties and good cleaning properties for flux residue, that are inhibited from changing in viscosity over time when stored at 30°C, and that are capable of inhibiting discoloration of the flux residue. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a photograph showing the state of a copper plate after solder paste has been printed and reflowed, and a diagram showing the criteria for evaluating reflowability. DETAILED DESCRIPTION OF THE INVENTION

[0019] (Flux) The flux of this embodiment contains rosin, a thixotropic agent, an activator, and a solvent.

[0020] <Rosin> In the present invention, "rosin" includes natural resins containing abietic acid as the main component, including a mixture of abietic acid and its isomers, as well as chemically modified natural resins (sometimes referred to as rosin derivatives). The abietic acid content in natural resins is, for example, 40% by mass or more and 80% by mass or less. Representative isomers of abietic acid include neoabietic acid, palustric acid, and levopimaric acid. The structure of abietic acid is shown below. In this specification, the term "main component" refers to a component that is contained in a compound in an amount of 40 mass % or more.

[0021] [ka]

[0022] In the present invention, the term "chemically modified natural resin (rosin derivative)" includes the "natural resin" that has been subjected to one or more treatments selected from the group consisting of hydrogenation, dehydrogenation, neutralization, alkylene oxide addition, amidation, dimerization, oligomerization, esterification, and Diels-Alder cycloaddition.

[0023] 《Specific rosin》 The rosin contained in the flux of this embodiment includes one or more specific rosins selected from the group consisting of acid-modified rosin, hydrogenated rosin, and acid-modified hydrogenated rosin. Examples of acid-modified rosins include acid-modified disproportionated rosin, acid anhydride-modified disproportionated rosin, phenol-modified rosin, α,β-unsaturated carboxylic acid-modified products (acrylated rosin, maleated rosin, fumarated rosin, etc.), purified products and disproportionated products of the α,β-unsaturated carboxylic acid-modified products, and acid-modified rosin soap. Hydrogenated rosins include those obtained by hydrogenating natural resins containing a mixture of abietic acid and its isomers, such as rosins containing dihydroabietic acid and tetrahydroabietic acid as the main components. Examples of the acid-modified hydrogenated rosin include acrylic acid-modified hydrogenated rosin, acid anhydride-modified hydrogenated rosin, and hydrogenated products of the α,β-unsaturated carboxylic acid-modified products.

[0024] The specific rosin may be used alone or in combination of two or more. As the specific rosin, it is preferable to use one or more types selected from the group consisting of hydrogenated rosin and acid-modified hydrogenated rosin. As the acid-modified hydrogenated rosin, it is preferable to use acrylic acid-modified hydrogenated rosin, and as the hydrogenated rosin, it is preferable to use rosin containing dihydroabietic acid and tetrahydroabietic acid as main components.

[0025] The content of the specific rosin in the flux is preferably 10% by mass or more and 70% by mass or less, more preferably 15% by mass or more and 60% by mass or less, and even more preferably 20% by mass or more and 50% by mass or less, relative to the total amount of the flux (100% by mass).

[0026] Other rosins The rosin may contain other rosins in addition to the specific rosin. Examples of other rosins include raw rosins such as gum rosin, wood rosin, and tall oil rosin, distilled rosin, and rosin derivatives other than the specific rosin.

[0027] Examples of rosin derivatives other than the specific rosin include purified rosin and modified rosin other than the specific rosin. Examples of modified rosins other than the specific rosin include polymerized rosin, polymerized hydrogenated rosin, disproportionated rosin, rosin ester, purified products, hydrogenated products and disproportionated products of the polymerized rosin, rosin alcohol, rosin amine, hydrogenated rosin ester, and rosin soap.

[0028] Examples of rosin amines include dehydroabietylamine and dihydroabietylamine. The rosin amine means a so-called disproportionated rosin amine. The structures of dehydroabietylamine and dihydroabietylamine are shown below.

[0029] [ka]

[0030] The total content of the rosin in the flux is preferably 10% by mass or more and 70% by mass or less, and more preferably 20% by mass or more and 50% by mass or less, relative to the total amount of the flux (100% by mass). The content of the specific rosin in the flux is preferably 20% by mass or more and 100% by mass or less, more preferably 40% by mass or more and 100% by mass or less, even more preferably 50% by mass or more and 100% by mass or less, and particularly preferably 65% ​​by mass or more and 100% by mass or less, relative to the total content of the rosins (100% by mass). By ensuring that the content of the specific rosin is within the above range, it is possible to reduce coloration of the flux residue and improve reflowability.

[0031] <Thixotropic agent> The thixotropic agent contained in the flux of this embodiment includes a specific thixotropic agent.

[0032] <<Specific thixotropic agent>> The specific thixotropic agent is a compound represented by the following general formula (1).

[0033] [ka] [In the formula, R 11 and R 12 R each independently represents a hydrocarbon group having 1 to 3 carbon atoms which may have a substituent, or a single bond. 21 and R 22 R each independently represents a hydrocarbon group having 7 to 29 carbon atoms which may have a substituent. 13 is a substituent, and n represents an integer of 0 to 4.

[0034] R 11 and R 12 are each independently preferably a hydrocarbon group having one carbon atom which may have a substituent or a single bond, more preferably a hydrocarbon group having one carbon atom which may have a substituent, and even more preferably a methylene group (—CH—).

[0035] R 21 and R 22 are each independently preferably a hydrocarbon group having 9 to 25 carbon atoms which may have a substituent, more preferably a hydrocarbon group having 11 to 21 carbon atoms which may have a substituent, even more preferably a hydrocarbon group having 13 to 19 carbon atoms which may have a substituent, and particularly preferably a hydrocarbon group having 15 to 19 carbon atoms which may have a substituent. R 21 and R 22 When R has a substituent, examples of the substituent include a hydroxyl group, -CONH2, an amino group (-NH2), a carboxyl group, etc. 21 and R 22 The substituent that may be possessed by is preferably a hydroxyl group. R 11 -NHCO-R 21 The bonding position of R on the benzene ring 12 -NHCO-R 22 It is preferably in a meta or para position relative to the bonding position on the benzene ring, and more preferably in a meta position.

[0036] R 13 is preferably a hydrocarbon group having 1 to 5 carbon atoms, a hydroxyl group or a halogen atom, and more preferably a hydrocarbon group having 1 to 5 carbon atoms. Preferably, n is 0.

[0037] The compound represented by the general formula (1) is preferably at least one selected from the group consisting of m-xylylenebislauric acid amide, m-xylylenebisbehenic acid amide, m-xylylenebisdihydroxystearic acid amide, m-xylylenebisstearic acid amide, m-xylylenebishydroxystearic acid amide, p-xylylenebishydroxystearic acid amide, m-phenylenebishydroxystearic acid amide, and p-phenylenebishydroxystearic acid amide, and more preferably a compound represented by the following formula (2): The compound represented by the following formula (2) is m-xylylenebishydroxystearic acid amide. The specific thixotropic agent may be used alone or in combination of two or more.

[0038] [ka]

[0039] Other thixotropic agents The thixotropic agent contained in the flux of this embodiment may include, in addition to the specific thixotropic agent, other thixotropic agents such as an ester-based thixotropic agent, an amide-based thixotropic agent other than the compound represented by the general formula (1) above, and a sorbitol-based thixotropic agent.

[0040] Examples of the ester-based thixotropic agent include ester compounds, and specific examples thereof include hydrogenated castor oil and ethyl myristate.

[0041] Examples of the amide-based thixotropic agent include monoamides, bisamides other than the compounds represented by the general formula (1), and polyamides. Examples of monoamides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, saturated fatty acid amide, oleic acid amide, erucic acid amide, unsaturated fatty acid amide, 4-methylbenzamide (p-toluamide), p-toluenemethane amide, aromatic amide, hexamethylenehydroxystearic acid amide, substituted amides, methylolstearic acid amide, methylol amide, fatty acid ester amide, and other monoamides. Examples of bisamides include methylene bisstearic acid amide, ethylene bislauric acid amide, ethylene bishydroxy fatty acid (fatty acid carbon number: C6 to C24) amide, ethylene bishydroxystearic acid amide, saturated fatty acid bisamide, methylene bisoleic acid amide, unsaturated fatty acid bisamide, and aromatic bisamides other than the compounds represented by the general formula (1). Examples of polyamides include saturated fatty acid polyamides, unsaturated fatty acid polyamides, aromatic polyamides, 1,2,3-propanetricarboxylic acid tris(2-methylcyclohexylamide), cyclic amide oligomers, and non-cyclic amide oligomers.

[0042] Examples of the cyclic amide oligomer include amide oligomers obtained by cyclic polycondensation of dicarboxylic acid and diamine, amide oligomers obtained by cyclic polycondensation of tricarboxylic acid and diamine, amide oligomers obtained by cyclic polycondensation of dicarboxylic acid and triamine, amide oligomers obtained by cyclic polycondensation of tricarboxylic acid and triamine, amide oligomers obtained by cyclic polycondensation of dicarboxylic acid, tricarboxylic acid, and diamine, amide oligomers obtained by cyclic polycondensation of dicarboxylic acid, tricarboxylic acid, and triamine, amide oligomers obtained by cyclic polycondensation of dicarboxylic acid, diamine, and triamine, amide oligomers obtained by cyclic polycondensation of tricarboxylic acid, diamine, and triamine, amide oligomers obtained by cyclic polycondensation of dicarboxylic acid, tricarboxylic acid, diamine, and triamine, and amide oligomers obtained by cyclic polycondensation of dicarboxylic acid, tricarboxylic acid, diamine, and triamine.

[0043] The acyclic amide oligomer may be an amide oligomer obtained by acyclic polycondensation of a monocarboxylic acid with a diamine and / or triamine, or an amide oligomer obtained by acyclic polycondensation of a dicarboxylic acid and / or tricarboxylic acid with a monoamine. In the case of an amide oligomer containing a monocarboxylic acid or a monoamine, the monocarboxylic acid or monoamine functions as terminal molecules, resulting in an acyclic amide oligomer with a reduced molecular weight. Furthermore, when the acyclic amide oligomer is an amide compound obtained by acyclic polycondensation of a dicarboxylic acid and / or tricarboxylic acid with a diamine and / or triamine, it becomes an acyclic high-molecular-weight amide polymer. Furthermore, the acyclic amide oligomer also includes an amide oligomer obtained by acyclic condensation of a monocarboxylic acid with a monoamine.

[0044] Examples of sorbitol-based thixotropic agents include dibenzylidene-D-sorbitol, bis(4-methylbenzylidene)-D-sorbitol, (D-)sorbitol, monobenzylidene(-D-)sorbitol, and mono(4-methylbenzylidene)-(D-)sorbitol.

[0045] The other thixotropic agents may be used singly or in combination of two or more.

[0046] The total content of the thixotropic agent in the flux is preferably 0.5% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 20% by mass or less, and even more preferably 4.5% by mass or more and 10% by mass or less, relative to the total amount of the flux (100% by mass). The content of the compound represented by the general formula (1) in the flux is preferably 0.1 mass % or more and 20 mass % or less, more preferably 0.2 mass % or more and 15 mass % or less, even more preferably 0.4 mass % or more and 15 mass % or less, and particularly preferably 0.5 mass % or more and 10 mass % or less, relative to the total amount (100 mass %) of the flux.

[0047] The content of the specific thixotropic agent in the flux is preferably 5% by mass or more and 100% by mass or less, more preferably 11% by mass or more and 100% by mass or less, even more preferably 30% by mass or more and 100% by mass or less, particularly preferably 50% by mass or more and 100% by mass or less, and most preferably 60% by mass or more and 100% by mass or less, relative to the total content (100% by mass) of the thixotropic agents. By ensuring that the content ratio of the specific thixotropic agent is within the above range, it is possible to suppress an increase in viscosity when stored at 30°C and also to reduce a decrease in viscosity when stored at 30°C.

[0048] When the flux contains the ester-based thixotropic agent, the content of the ester-based thixotropic agent is preferably more than 0 mass% and not more than 10 mass%, more preferably more than 0 mass% and not more than 5 mass%, and even more preferably more than 0 mass% and not more than 4 mass%, relative to the total amount (100 mass%) of the flux.

[0049] <Activator> Examples of the activator contained in the flux of this embodiment include organic acid-based activators, halogen-based activators, and amine-based activators. The flux of this embodiment preferably contains one or more selected from the group consisting of organic acid-based activators and halogen-based activators.

[0050] <Organic acid surfactant> Examples of organic acid surfactants include glutaric acid, adipic acid, azelaic acid, eicosane diacid, citric acid, glycolic acid, succinic acid, salicylic acid, diglycolic acid, dipicolinic acid, dibutylaniline diglycolic acid, suberic acid, sebacic acid, thioglycolic acid, dithioglycolic acid, terephthalic acid, dodecanedioic acid, parahydroxyphenylacetic 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, methylparaben ... Examples of the carboxylic acid include carboxylic acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butanoic 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 obtained by adding hydrogen to dimer acid, and hydrogenated trimer acid, which is a hydrogenated product obtained by adding hydrogen to trimer acid.

[0051] Examples of dimer acids and trimer acids include dimer acids which are reaction products of oleic acid and linoleic acid, trimer acids which are reaction products of oleic acid and linoleic acid, dimer acids which are reaction products of acrylic acid, trimer acids which are reaction products of acrylic acid, dimer acids which are reaction products of methacrylic acid, trimer acids which are reaction products of methacrylic acid, dimer acids which are reaction products of acrylic acid and methacrylic acid, trimer acids which are reaction products of acrylic acid and methacrylic acid, dimer acids which are reaction products of oleic acid, trimer acids which are reaction products of oleic acid, dimer acids which are reaction products of linoleic acid, trimer acids which are reaction products of linolenic acid, trimer acids which are reaction products of linolenic acid, dimer acids which are reaction products of acrylic acid and oleic acid, trimer acids which are reaction products of acrylic acid and oleic acid, dimer acids which are reaction products of acrylic acid and linoleic acid, acrylic Examples of the dimer acid include a trimer acid which is a reaction product of acrylic acid and linoleic acid, a dimer acid which is a reaction product of acrylic acid and linoleic acid, a dimer acid which is a reaction product of methacrylic acid and oleic acid, a trimer acid which is a reaction product of methacrylic acid and linoleic acid, a dimer acid which is a reaction product of methacrylic acid and linoleic acid, a dimer acid which is a reaction product of methacrylic acid and linoleic acid, a dimer acid which is a reaction product of methacrylic acid and linoleic acid, a dimer acid which is a reaction product of methacrylic acid and linoleic acid, a dimer acid which is a reaction product of oleic acid and linolenic acid, a dimer acid which is a reaction product of linoleic acid and linolenic acid, a trimer acid which is a reaction product of linoleic acid and linolenic acid, a hydrogenated dimer acid which is a hydrogenated product of each of the above dimer acids, and a hydrogenated trimer acid which is a hydrogenated product of each of the above trimer acids. For example, dimer acid, the reaction product of oleic acid and linoleic acid, is a dimer with 36 carbon atoms. Also, trimer acid, the reaction product of oleic acid and linoleic acid, is a trimer with 54 carbon atoms.

[0052] The organic acid surfactants may be used alone or in combination of two or more. As the organic acid activator, it is preferable to use a carboxylic acid. The carboxylic acid is preferably an aliphatic carboxylic acid. The carboxylic acid is preferably an aliphatic dicarboxylic acid. As the aliphatic dicarboxylic acid, it is preferable to use one or more selected from the group consisting of glutaric acid and azelaic acid.

[0053] <Halogen-based activators> Examples of halogen-based activators include amine hydrohalides and organic halogen compounds other than amine hydrohalides.

[0054] Amine hydrohalides are compounds obtained by reacting an amine with a hydrogen halide. Examples of the amine include those exemplified in the "Amine Activators" section below. Examples of the hydrogen halide include chlorine, bromine, and iodine hydrides.

[0055] More specifically, examples of amine hydrohalides include cyclohexylamine hydrobromide, hexadecylamine hydrobromide, stearylamine hydrobromide, ethylamine hydrobromide, diphenylguanidine hydrobromide, ethylamine hydrochloride, stearylamine hydrochloride, diethylaniline hydrochloride, diethanolamine hydrochloride, 2-ethylhexylamine hydrobromide, pyridine hydrobromide, isopropylamine hydrobromide, diethylamine hydrobromide, dimethylamine hydrobromide, and dimethylamine hydrobromide. Hydrochloride, Rosinamine Hydrobromide, 2-Ethylhexylamine Hydrochloride, Isopropylamine Hydrochloride, Cyclohexylamine Hydrochloride, 2-Pipecoline Hydrobromide, 1,3-Diphenylguanidine Hydrochloride, Dimethylbenzylamine Hydrochloride, Hydrazine Hydrate Hydrobromide, Dimethylcyclohexylamine Hydrochloride, Trinonylamine Hydrobromide, Diethylaniline Hydrobromide, 2-Diethylaminoethanol Hydrobromide, 2-Diethylaminoethanol Hydrochloride, Ammonium Chloride, Diallylamine Hydrochloride, Diallylamine Aminomethylamine hydrobromide, diethylamine hydrochloride, triethylamine hydrobromide, triethylamine hydrochloride, hydrazine monohydrochloride, hydrazine dihydrochloride, hydrazine monohydrobromide, hydrazine dihydrobromide, pyridine hydrochloride, aniline hydrobromide, butylamine hydrochloride, hexylamine hydrochloride, n-octylamine hydrochloride, dodecylamine hydrochloride, dimethylcyclohexylamine hydrobromide, ethylenediamine dihydrobromide, rosinamine hydrobromide, 2-phenylimidazole hydrobromide, 4-benzyl Examples of the fluoride include pyridine hydrobromide, L-glutamic acid hydrochloride, N-methylmorpholine hydrochloride, betaine hydrochloride, 2-pipecoline hydroiodide, cyclohexylamine hydroiodide, 1,3-diphenylguanidine hydrofluoride, diethylamine hydrofluoride, 2-ethylhexylamine hydrofluoride, cyclohexylamine hydrofluoride, ethylamine hydrofluoride, rosinamine hydrofluoride, cyclohexylamine tetrafluoroborate, and dicyclohexylamine tetrafluoroborate.

[0056] Furthermore, examples of halogen-based activators that can be used include salts obtained by reacting amines with tetrafluoroboric acid (HBF4) and complexes obtained by reacting amines with boron trifluoride (BF3). Examples of the complex include boron trifluoride piperidine.

[0057] Examples of organic halogen compounds other than amine hydrohalides include halogenated aliphatic compounds having halogenated aliphatic hydrocarbon groups, which are aliphatic hydrocarbon groups in which some or all of the hydrogen atoms constituting the aliphatic hydrocarbon group have been substituted with halogen atoms. Examples of the halogenated aliphatic compounds include halogenated aliphatic alcohols and halogenated heterocyclic compounds.

[0058] 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.

[0059] Examples of the halogenated heterocyclic compound include compounds represented by the following general formula (3).

[0060] R 5 -(R 6 ) m (3) [In the formula, R 5 represents an m-valent heterocyclic group. 6 represents a halogenated aliphatic hydrocarbon group.

[0061] R 5In the above, the heterocyclic ring of the m-valent heterocyclic group may be a ring structure in which some of the carbon atoms constituting an aliphatic hydrocarbon ring or an aromatic hydrocarbon ring are substituted with heteroatoms. Examples of heteroatoms in this heterocyclic ring include oxygen atoms, sulfur atoms, and nitrogen atoms. This heterocyclic ring is preferably a 3- to 10-membered ring, and more preferably a 5- to 7-membered ring. Examples of this heterocyclic ring include an isocyanurate ring. R 6 The halogenated aliphatic hydrocarbon group in R preferably has 1 to 10 carbon atoms, more preferably has 2 to 6 carbon atoms, and even more preferably has 3 to 5 carbon atoms. 6 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.

[0062] Examples of halogenated heterocyclic compounds include tris-(2,3-dibromopropyl)isocyanurate.

[0063] Furthermore, examples of organic halogen compounds other than amine hydrohalides include halogenated carboxyl compounds such as iodinated carboxyl compounds, such as 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, and 5-iodoanthranilic acid; chlorinated carboxyl compounds, such as 2-chlorobenzoic acid and 3-chloropropionic acid; and brominated carboxyl compounds, such as 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid, and 2-bromobenzoic acid.

[0064] The halogen-based activators may be used alone or in combination of two or more. As the halogen-based activator, it is preferable to use an organic halogen compound, it is more preferable to use a halogenated aliphatic compound, and it is even more preferable to use a halogenated aliphatic alcohol. As the halogenated aliphatic alcohol, trans-2,3-dibromo-2-butene-1,4-diol is preferably used.

[0065] Amine surfactants Examples of the amine-based surfactant include rosin amine, azoles, guanidines, alkylamine compounds, and aminoalcohol compounds.

[0066] Examples of rosin amines include those exemplified above in "Other rosins."

[0067] Examples of azoles include 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, and 1-cyanoethyl-2-ethylimidazole. 1-cyanoethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl- s-Triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazo Phosphorus, 2,4-diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyl-s-triazine, epoxy-imidazole adduct, 2-methylbenzimidazole, 2-octylbenzimidazole, 2-pentylbenzimidazole, 2-(1-ethylpentyl)benzimidazole, 2-nonylbenzimidazole, 2-(4-thiazolyl)benzimidazole, benzimidazole, 1,2,4-Triazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol], 6-(2-benzotriazolyl)-4-tert-octyl-6'-tert-butyl-4'-methyl-2,2'-methylenebisphenol, 1,2,3-benzotriazolyl Examples of the benzotriazole include 1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, carboxybenzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, 2,2'-[[(methyl-1H-benzotriazol-1-yl)methyl]imino]bisethanol, 1-(1',2'-dicarboxyethyl)benzotriazole, 1-(2,3-dicarboxypropyl)benzotriazole, 1-[(2-ethylhexylamino)methyl]benzotriazole, 2,6-bis[(1H-benzotriazol-1-yl)methyl]-4-methylphenol, 5-methylbenzotriazole, and 5-phenyltetrazole.

[0068] 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.

[0069] Examples of alkylamine compounds include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, and stearylamine.

[0070] Examples of amino alcohol compounds include N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine.

[0071] The amine-based surfactants may be used alone or in combination of two or more.

[0072] The total content of the activator in the flux is preferably 0.2% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less, and even more preferably 1% by mass or more and 10% by mass or less, relative to the total amount of the flux (100% by mass). Alternatively, the total content of the activator in the flux may be 1% by mass or more and 20% by mass or less with respect to the total amount (100% by mass) of the flux.

[0073] The content of the organic acid-based activator in the flux is preferably 0% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 15% by mass or less, even more preferably 2% by mass or more and 10% by mass or less, and particularly preferably 5% by mass or more and 10% by mass or less, relative to the total amount (100% by mass) of the flux.

[0074] The content of the halogen-based activator in the flux is preferably 0% by mass or more and 5% by mass or less, more preferably 0% by mass or more and 3% by mass or less, even more preferably 0.5% by mass or more and 3% by mass or less, and particularly preferably 1% by mass or more and 3% by mass or less, relative to the total amount (100% by mass) of the flux.

[0075] <Solvent> Examples of the solvent include water, alcohol-based solvents, glycol ether-based solvents, and terpineols. Examples of alcohol-based solvents include isopropyl alcohol, 1,2-butanediol, isobornylcyclohexanol, 2,4-diethyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyne-2,5-diol, 2,3-dimethyl-2,3-butanediol, 2-methylpentane-2,4-diol, and 1,1,1-tris(hydroxymethyl)propanediol. Examples of suitable hydroxypropyl methyl ethers include 2,2'-bis(hydroxymethyl)-1,3-propanediol, 2,2'-oxybis(methylene)bis(2-ethyl-1,3-propanediol), 2,2-bis(hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and 2,4,7,9-tetramethyl-5-decyne-4,7-diol. Examples of glycol ether solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, diethylene glycol monohexyl ether (hexyl diglycol), diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, methyl propylene triglycol, butyl propylene triglycol, triethylene glycol butyl methyl ether, and tetraethylene glycol dimethyl ether.

[0076] The solvent may be used alone or in combination of two or more. As the solvent, it is preferable to use a glycol ether solvent. As the glycol ether solvent, hexyl diglycol is preferably used.

[0077] The total content of the solvents in the flux is preferably 20% by mass or more and 80% by mass or less, more preferably 30% by mass or more and 75% by mass or less, and even more preferably 37% by mass or more and 67% by mass or less, relative to the total amount of the flux (100% by mass).

[0078] <Other ingredients> The flux in this embodiment may contain other components as needed in addition to the rosin, the thixotropic agent, the activator, and the solvent. Examples of other components include resin components other than rosin, metal deactivators, surfactants, silane coupling agents, antioxidants, and the like.

[0079] Resin components other than rosin: Examples of resin components 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 epoxy resins. Examples of modified terpene resins include aromatic modified terpene resins, hydrogenated terpene resins, and hydrogenated aromatic modified terpene resins. Examples of modified terpene phenolic resins include hydrogenated terpene phenolic resins. Examples of modified styrene resins include styrene acrylic resins and styrene maleic acid resins. Examples of modified xylene resins include phenol-modified xylene resins, alkylphenol-modified xylene resins, phenol-modified resol-type xylene resins, polyol-modified xylene resins, and polyoxyethylene-added xylene resins.

[0080] Metal deactivator: Examples of metal deactivators include hindered phenol compounds and nitrogen compounds. The term "metal deactivator" as used herein refers to a compound that has the ability to prevent metals from deteriorating when in contact with certain compounds.

[0081] The hindered phenol compound refers to a phenol compound having a bulky substituent (for example, a branched or cyclic alkyl group such as a t-butyl group) at least on one of the ortho positions of the phenol. The hindered phenol compound is not particularly limited, and examples thereof include bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylenebis(oxyethylene)], N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2'-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-octanol) (ethylthio)-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 (3,5-di-tert-butyl-4-hydroxy-hydrocinnamamide), 3,5-di-tert-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxamide, and compounds represented by the following chemical formula.

[0082] [ka] [wherein Z is an optionally substituted alkylene group. R 1 and R2 R is each independently an optionally substituted alkyl group, aralkyl group, aryl group, heteroaryl group, cycloalkyl group, or heterocycloalkyl group. 3 and R 4 are each independently an optionally substituted alkyl group.

[0083] Examples of the nitrogen compound in the metal deactivator include hydrazide-based nitrogen compounds, amide-based nitrogen compounds, triazole-based nitrogen compounds, and melamine-based nitrogen compounds.

[0084] The hydrazide nitrogen compound may be any nitrogen compound having a hydrazide skeleton, and examples thereof include dodecanedioic acid bis[N2-(2-hydroxybenzoyl)hydrazide], N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, decanedicarboxylic acid disalicyloylhydrazide, N-salicylidene-N'-salicylhydrazide, m-nitrobenzhydrazide, 3-aminophthalhydrazide, phthalic acid dihydrazide, adipic acid hydrazide, oxalobis(2-hydroxy-5-octylbenzylidenehydrazide), N'-benzoylpyrrolidonecarboxylic acid hydrazide, and N,N'-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hydrazine.

[0085] The amide nitrogen compound may be any nitrogen compound having an amide skeleton, and examples thereof include N,N'-bis{2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxyl]ethyl}oxamide.

[0086] The triazole-based nitrogen compound may be any nitrogen compound having a triazole skeleton, and examples thereof include N-(2H-1,2,4-triazol-5-yl)salicylamide, 3-amino-1,2,4-triazole, and 3-(N-salicyloyl)amino-1,2,4-triazole.

[0087] The melamine-based nitrogen compound may be any nitrogen compound having a melamine skeleton, such as melamine, melamine derivatives, etc. More specific examples include trisaminotriazine, alkylated trisaminotriazine, alkoxyalkylated trisaminotriazine, melamine, alkylated melamine, alkoxyalkylated melamine, N2-butylmelamine, N2,N2-diethylmelamine, N,N,N',N',N'',N''-hexakis(methoxymethyl)melamine, etc.

[0088] Examples of the surfactant include nonionic surfactants and weak cationic surfactants. Examples of nonionic surfactants include polyethylene glycol, polyethylene glycol-polypropylene glycol copolymers, aliphatic alcohol polyoxyethylene adducts, aromatic alcohol polyoxyethylene adducts, and polyhydric alcohol polyoxyethylene adducts. Examples of weakly cationic surfactants include diamine-terminated polyethylene glycol, diamine-terminated polyethylene glycol-polypropylene glycol copolymer, aliphatic amine polyoxyethylene adduct, aromatic amine polyoxyethylene adduct, and polyvalent amine polyoxyethylene adduct.

[0089] Examples of surfactants other than those mentioned above include polyoxyalkylene acetylene glycols, polyoxyalkylene glyceryl ethers, polyoxyalkylene alkyl ethers, polyoxyalkylene esters, polyoxyalkylene alkylamines, and polyoxyalkylene alkylamides.

[0090] The flux of the present embodiment described above contains one or more selected from the group consisting of acid-modified rosin, hydrogenated rosin, and acid-modified hydrogenated rosin, and a specific thixotropic agent, and thereby can suppress an increase in viscosity when stored at 30°C. The flux of this embodiment contains the specific thixotropic agent, which improves the cleaning properties of flux residue and also sufficiently suppresses a decrease in viscosity when stored at 30°C. The flux of the present embodiment contains one or more selected from the group consisting of acid-modified rosin, hydrogenated rosin, and acid-modified hydrogenated rosin, thereby making it possible to ensure sufficient reflowability and sufficiently suppress coloration of flux residue. The flux of this embodiment has a synergistic effect of combining one or more selected from the group consisting of acid-modified rosin, hydrogenated rosin, and acid-modified hydrogenated rosin with a specific thixotropic agent, which results in good reflowability and good cleaning properties for flux residue, as well as suppressing changes in viscosity over time when stored at 30°C and suppressing discoloration of flux residue.

[0091] (solder paste) The solder paste of this embodiment contains a solder alloy powder and the above-described flux.

[0092] The solder alloy powder may be composed of a powder of solder containing only Sn, or a powder of a solder alloy such as Sn-Ag, Sn-Cu, Sn-Ag-Cu, Sn-Bi, or Sn-In, or an alloy of these to which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, or P has been added. The solder alloy powder may be composed of a powder of a solder alloy of Sn-Pb system or a Sn-Pb system to which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. have been added. The solder alloy powder is preferably a Pb-free solder.

[0093] Flux Content: The content of the flux in the solder paste is preferably 5 to 30 mass % relative to the total mass of the solder paste, and more preferably 5 to 15 mass %.

[0094] The solder paste of this embodiment uses a flux containing one or more selected from the group consisting of acid-modified rosin, hydrogenated rosin, and acid-modified hydrogenated rosin, and a specific thixotropic agent, thereby making it possible to suppress changes in viscosity over time when stored at 30°C. The solder paste of this embodiment contains the above-mentioned flux, and thus can fully exhibit the effects of the present invention. [Example]

[0095] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0096] <Preparation of flux> (Examples 1 to 10, Comparative Examples 1 to 10) Each flux of the examples and comparative examples was prepared according to the compositions shown in Tables 1 to 5. The raw materials used are listed below. Examples 1 to 6, 9, and 10 are treated as reference examples.

[0097] Specific rosin: acrylic acid modified hydrogenated rosin, hydrogenated rosin The hydrogenated rosin used was a rosin containing dihydroabietic acid and tetrahydroabietic acid as main components. Other rosins: rosin ester, polymerized rosin

[0098] Specific thixotropic agent: m-xylylene bishydroxystearic acid amide Amide-based thixotropic agents: polyamide, N,N'-bis(2-stearamidoethyl)-azelaicamide, ethylene bishydroxystearic acid amide Ester thixotropic agent: hydrogenated castor oil

[0099] Activators: glutaric acid, azelaic acid, trans-2,3-dibromo-2-butene-1,4-diol

[0100] Solvent: Hexyldiglycol

[0101] <Preparation of solder paste> The flux of each example was mixed with the solder alloy powder shown below to prepare a solder paste. Each of the prepared solder pastes contained 13 mass % of flux and 87 mass % of solder alloy powder.

[0102] The solder alloy powder is a powder made of a solder alloy containing 3 mass % Ag, 0.5 mass % Cu, and the remainder Sn. The solder alloy powder has a size (particle size distribution) that satisfies symbol 6 in the powder size classification (Table 2) of JIS Z 3284-1:2014.

[0103] The solder paste prepared above was evaluated according to the evaluation methods described in the <Evaluation> below for the following: <Evaluation of viscosity increase when stored at 30°C>, <Evaluation of viscosity decrease when stored at 30°C>, <Evaluation of reflowability>, <Evaluation of flux residue cleanability>, and <Evaluation of flux residue color>. The results of these evaluations are shown in Tables 1 to 5.

[0104] <Evaluation> <Evaluation of viscosity increase when stored at 30°C> How to verify: First, the viscosity of each prepared solder paste was measured using a rotational viscometer (PCU-205, manufactured by Malcom Co., Ltd.) at a rotation speed of 10 rpm and a measurement temperature of 25°C. Each solder paste was then stored at 30°C for 24 hours. The viscosity of the solder paste after storage was then measured using the same method as that used to measure the viscosity of the solder paste before storage. The viscosity before storage was compared with the viscosity after storage, and evaluation was performed based on the following criteria. Judgment criteria: A: Viscosity after storage < Viscosity before storage x 1.25 Viscosity increase is small and viscosity stability over time is good B: Viscosity after storage ≧ Viscosity before storage × 1.25 Viscosity increase is large and stability of viscosity over time is poor

[0105] <Evaluation of viscosity decrease when stored at 30°C> How to verify: The viscosity was measured in the same manner as in the above <<Evaluation of viscosity increase upon storage at 30°C>>. Judgment criteria: A: Viscosity after storage > initial viscosity x 0.85. Viscosity decrease over time is small, and viscosity stability is good. B: Viscosity after storage ≦ Initial viscosity × 0.85 The viscosity decreased significantly over time, and the viscosity stability was poor.

[0106] <Evaluation of reflowability> How to verify: Using a metal mask (0.2 mm thick, opening φ6.5 mm), solder paste was printed on a copper plate. The copper plate on which the solder paste was printed was reflowed in a nitrogen atmosphere to melt the solder paste. Judgment criteria: A: The solder paste is molten and shiny. B: The solder paste is not melted sufficiently and is lackluster. The criteria for evaluating reflowability after reflowing a copper plate with printed solder paste is shown in Figure 1. In Figure 1, A indicates that the reflowability was evaluated according to criterion A, and B indicates that the reflowability was evaluated according to criterion B.

[0107] <Evaluation of cleaning ability of flux residue> How to verify: Solder paste was printed on a copper plate using a metal mask (0.2 mm thick, opening φ6.5 mm). The copper plate with the printed solder paste was reflowed in a nitrogen atmosphere to melt the solder paste. After reflow, the copper plate was immersed in a cleaning solution at 30°C and subjected to ultrasonic waves for 5 minutes. Toho Clean W-312 was used as the cleaning solution. Next, the presence or absence of flux residue on the copper plate after cleaning was confirmed and evaluated based on the following criteria.

[0108] Judgment criteria: A: No flux residue was observed on the copper plate. B: Flux residue was observed on the copper plate.

[0109] <Evaluation of flux residue color> How to verify: Solder paste was printed on a copper plate using a metal mask (0.2 mm thick, opening φ6.5 mm). The copper plate with the printed solder paste was reflowed in a nitrogen atmosphere to melt the solder paste. The color of the flux residue was then evaluated based on the following criteria.

[0110] Judgment criteria: A: The flux residue was colorless. B: The flux residue was discolored.

[0111] [Table 1]

[0112] As shown in Table 1, the flux of Example 1 containing the specific rosin and the specific thixotropic agent was evaluated as A in the following areas: viscosity increase when stored at 30°C, viscosity decrease when stored at 30°C, reflowability, cleaning ability of flux residue, and color of flux residue. In contrast, the flux of Comparative Example 1, which did not contain the specific thixotropic agent but contained hardened castor oil, was evaluated as B for the increase in viscosity when stored at 30°C. The flux of Comparative Example 2, which did not contain the specific thixotropic agent but contained polyamide, was evaluated as B in terms of cleaning ability of flux residue. The flux of Comparative Example 3, which did not contain the specific thixotropic agent but contained N,N'-bis(2-stearamidoethyl)-azelicamide, was evaluated as B in terms of cleaning ability of flux residue. The flux of Comparative Example 4, which did not contain the specific thixotropic agent but contained ethylene bishydroxystearic acid amide, was evaluated as B in terms of viscosity reduction when stored at 30°C and in terms of cleaning ability of flux residue.

[0113] [Table 2]

[0114] As shown in Table 2, the fluxes of Examples 7 and 8, which contained a specific thixotropic agent and hardened castor oil, were evaluated as A in terms of the increase in viscosity when stored at 30°C. In contrast, as shown in Table 2, the fluxes of Comparative Examples 5 and 6, which did not contain a specific thixotropic agent but contained hardened castor oil, were evaluated as B in terms of the increase in viscosity when stored at 30°C.

[0115] As shown in Table 2, the fluxes of Examples 7 and 8, which contained the specific rosin, were rated A in terms of reflowability and color of flux residue. In contrast, as shown in Table 2, the flux of Comparative Example 7 containing rosin ester was evaluated as B in terms of reflowability. The flux of Comparative Example 8 containing polymerized rosin was rated B for the color of the flux residue.

[0116] [Table 3]

[0117] As shown in Table 3, the flux of Example 1 containing the specific rosin was rated A in terms of reflowability and color of flux residue. In contrast, as shown in Table 3, the flux of Comparative Example 9 containing rosin ester was evaluated as B in terms of reflowability. The flux of Comparative Example 10 containing polymerized rosin was rated B for the color of the flux residue.

[0118] [Table 4]

[0119] As shown in Table 4, the fluxes of Examples 2 to 6 and Examples 9 to 10 were evaluated as A in terms of the increase in viscosity when stored at 30°C, the decrease in viscosity when stored at 30°C, the reflow property, the cleanability of flux residue, and the color of flux residue.

[0120] [Table 5]

[0121] Table 5 shows the viscosity increase rate (%) of the fluxes of Examples 1, 6, 8 and Comparative Example 5 when stored at 30°C. The viscosity increase rate means the rate of increase in viscosity after storage relative to the viscosity before storage when stored at 30°C as described in "Evaluation of viscosity increase when stored at 30°C."

[0122] As shown in Table 5, the flux of Comparative Example 5, which did not contain a specific thixotropic agent but contained acrylic acid-modified hydrogenated rosin and castor hardened oil, showed a change in viscosity over time (viscosity increase rate) of 40.0% when stored at 30°C. In contrast, the flux of Example 8, which contained 0.5 mass % of the specific thixotropic agent, acrylic acid-modified hydrogenated rosin, and castor hardened oil, showed a change in viscosity over time of 21.3% when stored at 30°C. Furthermore, the flux of Example 1, which contained 8 mass % of the specific thixotropic agent and acrylic acid-modified hydrogenated rosin, showed a change in viscosity over time of 16.0% when stored at 30°C. Furthermore, the flux of Example 6, which contained 8 mass % of the specific thixotropic agent and hydrogenated rosin, showed a change in viscosity over time of 19.3% when stored at 30°C. It has been revealed that the flux of the present invention, even if it contains acrylic acid-modified hydrogenated rosin or hydrogenated rosin, can suppress the change in viscosity over time when stored at 30°C by containing a specific thixotropic agent. [Industrial Applicability]

[0123] The present invention can provide a flux and a solder paste that have good reflow properties and good cleaning properties for flux residue, and that are inhibited from changing in viscosity over time when stored at 30°C, and that can inhibit coloration of the flux residue. This flux and solder paste can be suitably used for soldering that involves reflow.

Claims

1. Contains rosin, a thixotropic agent, an activator, and a solvent, The rosin includes at least one selected from the group consisting of acid-modified rosin, hydrogenated rosin, and acid-modified hydrogenated rosin, The thixotropic agent includes a compound represented by the following general formula (1): The thixotropic agent further includes an ester-based thixotropic agent, the content of the ester-based thixotropic agent is more than 0 mass % and 4 mass % or less with respect to the total mass of the flux, A flux in which the content of the compound represented by the following general formula (1) is 11 mass % or more relative to the total content (100 mass %) of the thixotropic agent: 【Chemical 1】 [In the formula, R １１ and R １２ R each independently represents a hydrocarbon group having 1 to 3 carbon atoms which may have a substituent, or a single bond. ２１ and R ２２ R each independently represents a hydrocarbon group having 7 to 29 carbon atoms and a hydroxyl group. １３ is a substituent, and n represents an integer of 0 to 4.

2. 2. The flux according to claim 1, wherein the content of the compound represented by the general formula (1) is 0.5 mass % or more and 10 mass % or less with respect to the total mass of the flux.

3. 3. The flux according to claim 1, wherein the content of the activator is 1 mass % or more and 20 mass % or less with respect to the total mass of the flux.

4. A solder paste comprising a solder alloy powder and the flux according to claim 1 or 2.

5. A solder paste comprising a solder alloy powder and the flux according to claim 3.

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