Water-soluble flux and solder paste

Abstract

A water-soluble flux capable of further suppressing the occurrence of voids contains a keto acid with a melting point of 40°C or lower and a solvent with a boiling point of 240°C or lower.

Description

Technology Field

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

[0002] The present application claims priority based on Japanese Patent Application No. 2021-183673 filed on November 10, 2021, and incorporates the contents thereof herein. Background Technology

[0003] Fixing of components to a substrate and electrical connection of components to a substrate are generally performed by soldering. In soldering, flux, solder powder, and solder paste mixed with flux and solder powder are used.

[0004] Flux has the ability to chemically remove metal oxides present on the metal surface of the object to be soldered and on the solder, and to enable the movement of metal elements at the boundary between the two. For this reason, by performing soldering using flux, an intermetallic compound is formed between the two, thereby enabling a strong bond to be obtained.

[0005] In soldering using solder paste, first, solder paste is printed on a substrate, then a component is mounted, and the substrate with the component mounted on it is heated in a heating furnace called a reflow furnace. By doing so, the solder powder contained in the solder paste melts, and the component can be soldered to the substrate.

[0006] Generally, flux contains resin components, solvents, activators, thixotropic agents, etc. In order to increase the reliability of the bonding between the solder and the object to be joined, excess flux after soldering is removed by cleaning. Flux that remains even after cleaning is called flux residue.

[0007] Conventionally, rosin, which has excellent electrical insulation and moisture resistance, has been used as the resin component in flux. However, fluxes containing rosin have sometimes caused problems in terms of safety and the environment because they require organic solvents for cleaning after soldering. Therefore, there has been a demand for a water-soluble flux that can be easily cleaned with water after soldering.

[0008] In this regard, Patent Document 1 describes a flux containing an organic acid polyglycerol ester, a thixotropic agent, and a solvent having a specific SP value. According to the flux described in Patent Document 1, it is believed that the water-cleanability after soldering can be improved. Prior art literature

[0009] Patent Document 1: Japanese Patent Publication No. 2016-43398 The problem to be solved

[0010] Recently, miniaturized components such as QFNs (Quad Flat Non-Leaded Packages) are being used. Since QFNs do not have leads around the package and have the exposed surface of the lead frame and electrode terminals on the back of the package, when soldering a QFN, the back of the QFN and the surface of the substrate are bonded with solder paste.

[0011] When the exposed surface of the lead frame and the electrode terminals on the back of a package such as a QFN are soldered to a substrate, flux residue is likely to remain on the back of the package. Furthermore, the flux residue remaining on the back of the package causes the occurrence of voids. In this regard, it is difficult to suppress the occurrence of voids in the solder paste using the flux described in Patent Document 1.

[0012] Herein, the present invention aims to provide a flux and a solder paste capable of further suppressing the occurrence of voids. means of solving the problem

[0013] In order to solve the above problem, the present invention adopts the following configuration.

[0014] That is, the first aspect of the present invention is a water-soluble flux containing a keto acid having a melting point of 40°C or lower and a solvent having a boiling point of 240°C or lower.

[0015] In the water-soluble flux according to the first sun, the keto acid is additionally preferably at a boiling point of 250°C or lower.

[0016] In the water-soluble flux according to the first sun, the content of the keto acid is preferably 10 to 25 mass% with respect to the total mass (100 mass%) of the water-soluble flux.

[0017] In the water-soluble flux according to the first sun, it is preferable that the keto acid comprises an organic acid having one carboxyl group in its molecule.

[0018] In the water-soluble flux according to the first sun, it is preferable that the keto acid includes levulinic acid.

[0019] In the water-soluble flux according to the first sun, the ratio of the keto acid to the solvent is preferably 0.60 to 4.0 in mass ratio expressed as solvent / keto acid.

[0020] In the water-soluble flux according to the first sun, it is preferable to additionally contain a nonionic surfactant and an amine.

[0021] In the water-soluble flux according to the first sun, it is preferable not to contain one or more resin components selected from the group consisting of rosin and thermosetting resin.

[0022] In addition, a second aspect of the present invention is a solder paste containing solder alloy powder and a water-soluble flux according to the first aspect. Effects of the invention

[0023] According to the present invention, a flux and a solder paste capable of further suppressing the occurrence of voids can be provided. Brief explanation of the drawing

[0024] [Fig. 1] This is a drawing showing the reflow profile in the evaluation of the void area ratio. Specific details for implementing the invention

[0025] (Water-soluble flux)

[0026] The water-soluble flux according to the present embodiment contains a keto acid and a solvent.

[0027] In this specification, "water-soluble flux" refers to a flux whose flux residue can be removed by washing with water. Hereinafter, water-soluble flux may be simply referred to as "flux."

[0028] In this specification, the boiling point refers to the temperature of a liquid at which the saturated vapor pressure of the liquid in question becomes equal to 1 atmosphere (i.e., 1013 hPa).

[0029] In addition, in this specification, the term "melting point" refers to the temperature at which a solid melts and becomes a liquid. The melting point values ​​of compounds in this specification are mainly those listed in the "Chemical Handbook Basic Edition, 5th Revised Edition (Japan Chemical Society, Maruzen Publishing)."

[0030] Keto acid

[0031] Specific Keto Acids

[0032] The water-soluble flux according to the present embodiment contains a specific keto acid having a melting point of 40°C or lower. A keto acid is a compound containing a ketone group and a carboxyl group. In the present invention, the specific keto acid may be, for example, a compound represented by the following general formula (1).

[0033] It is preferable that the melting point of a specific keto acid be 38°C or lower. It is preferable that the melting point of a specific keto acid be 5°C or higher, more preferable that it be 10°C or higher, even more preferable that it be 15°C or higher, particularly preferable that it be 20°C or higher, and most preferable that it be 25°C or higher.

[0034] Since the melting point of a specific keto acid is below the upper limit mentioned above, it becomes easier to increase the fluidity of the flux residue even at lower temperatures. As a result, it becomes easier to discharge voids from the flux residue.

[0035]

[0036] [In the middle of the meal, R 1 It is a hydrocarbon group that may have substituents. R 2 is a hydrocarbon group or single bond that may have a substituent.

[0037] R 1 As hydrocarbon groups in the above, for example, chain hydrocarbon groups having 1 to 20 carbon atoms, alicyclic hydrocarbon groups having 3 to 20 carbon atoms, aromatic hydrocarbon groups, -OR 11 You can lift the back.

[0038] R 1 In the case of this chain hydrocarbon group, the chain hydrocarbon group may be a straight chain or a branched chain. The chain hydrocarbon group is a saturated hydrocarbon group or an unsaturated hydrocarbon group, and it is preferable that it be a saturated hydrocarbon group.

[0039] R 1 In the case of this alicyclic hydrocarbon group, the alicyclic hydrocarbon group may be a polycyclic group or a monocyclic group. As a monocyclic alicyclic hydrocarbon group, a group formed by removing one or more hydrogen atoms from a monocycloalkane is preferred. As a polycyclic alicyclic hydrocarbon group, a group formed by removing one or more hydrogen atoms from a polycycloalkane is preferred.

[0040] R 1Examples of substituents in include carbonyl groups, carboxyl groups, hydroxyl groups, amino groups, halogen atoms, etc. R 1 Examples of halogen atoms in this include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0041] R 1 In the case of this aromatic hydrocarbon group, the aromatic hydrocarbon group is a hydrocarbon group having at least one aromatic ring, and examples include aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene; aromatic heterocyclic rings in which some of the carbon atoms constituting the aromatic hydrocarbon ring are substituted with heterocyclic atoms; and condensed rings formed by the condensation of an aromatic hydrocarbon ring and an aromatic heterocyclic ring. 1 In the case where the aromatic hydrocarbon group has a substituent, the substituent may include a hydrocarbon group having 1 to 20 carbon atoms, a carboxyl group, a hydroxyl group, an amino group, a halogen atom, etc. When the substituent is a hydrocarbon group, the hydrocarbon group may be, for example, R 1 Examples of similar hydrocarbon groups in this regard can be cited.

[0042] -OR 11 R in 11 As for, the aforementioned, R 1 Examples of similar hydrocarbon groups in this regard can be cited.

[0043] R 1 As such, a chain hydrocarbon group is preferred. As for the number of carbon atoms in the chain hydrocarbon group, 1 to 10 is preferred, 1 to 5 is more preferred, 1 to 3 is even more preferred, and 1 is particularly preferred. Examples of hydrocarbon groups having 1 to 5 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, a neopentyl group, etc.

[0044] R 2Examples of hydrocarbon groups in this case include chain hydrocarbon groups having 1 to 20 carbon atoms, alicyclic hydrocarbon groups having 3 to 20 carbon atoms, aromatic hydrocarbon groups, etc. R 2 As a substituent in , R 1 The above-mentioned items can be cited in this regard.

[0045] R 2 In the case where the chain hydrocarbon group is a chain hydrocarbon group, the chain hydrocarbon group may be a straight chain or a branched chain. The chain hydrocarbon group is a saturated hydrocarbon group or an unsaturated hydrocarbon group, and it is preferable that it be a saturated hydrocarbon group.

[0046] R 2 As for the straight-chain hydrocarbon group in this case, a straight-chain alkylene group is preferred, and specifically, examples include a methylene group [-CH2-], an ethylene group [-(CH2)2-], a trimethylene group [-(CH2)3-], a tetramethylene group [-(CH2)4-], a pentamethylene group [-(CH2)5-], etc.

[0047] R 2 As for the branched-chain hydrocarbon group in the above, a branched-chain alkylene group is preferred, and specifically, alkyl methylene groups such as -CH(CH3)-, -CH(CH2CH3)-, -C(CH3) 2-, -C(CH3)(CH2CH3)-, -C(CH3)(CH2CH2CH3)-, -C(CH2CH3)2-; alkyl ethylene groups such as -CH(CH3)CH2-, -CH(CH3)CH(CH3)-, -C(CH3)2CH2-, -CH(CH2CH3)CH2-, -C(CH2CH3)2-CH2-; alkyl trimethylene groups such as -CH(CH3)CH2CH2-, -CH2CH(CH3)CH2-; Examples include alkyl alkylene groups such as alkyl tetramethylene groups such as -CH(CH3)CH2CH2CH2- and -CH2CH(CH3)CH2CH2-.

[0048] R 2 If is a cycloaliphatic hydrocarbon group, the cycloaliphatic hydrocarbon group is R 1In this regard, one hydrogen atom removed from the aforementioned alicyclic hydrocarbon group can be cited.

[0049] R 2 If is an aromatic hydrocarbon group, the aromatic hydrocarbon group is R 1 In this regard, one hydrogen atom removed from the aforementioned aromatic hydrocarbon group can be cited.

[0050] R 2 As such, chain hydrocarbon groups are preferred, and straight hydrocarbon groups are more preferred.

[0051] The number of carbon atoms in the above chain hydrocarbon group is preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3. As for the above chain hydrocarbon group, a methylene group, an ethylene group, or a trimethylene group is preferred.

[0052] Specific keto acids include, for example, pyruvate (melting point: 13.6°C, boiling point: 165°C), levulinic acid (melting point: 37.2°C, boiling point: 245°C), 3-oxobutanoic acid (melting point: 36.5°C), 5-oxohexanoic acid (melting point: 13°C, boiling point: 274°C), 6-oxoheptanoic acid (melting point: 36°C, boiling point: 335°C), 7-oxooctanic acid (melting point: 28°C, boiling point: 370°C), 2-oxobutanoic acid (melting point: 32°C, boiling point: 208°C), and 2-oxopentanic acid (melting point: 7°C, boiling point: 230°C).

[0053] Specific keto acids may be used as a single type or as a mixture of two or more types.

[0054] It is preferable that the specific keto acid contains an organic acid having one carboxyl group in its molecule. This makes it easier to suppress the occurrence of voids.

[0055] It is preferable that the specific keto acid includes one or more selected from the group consisting of pyruvate and levulinic acid, and it is more preferable that it includes levulinic acid.

[0056] The boiling point (Tk) of a specific keto acid is preferably 150°C or higher, more preferably 200°C or higher, particularly preferably 220°C or higher, and most preferably 230°C or higher. Since Tk is above the lower limit, it becomes easier to suppress the complete volatilization of the specific keto acid during reflow. Furthermore, the specific solvent is more likely to volatilize before the specific keto acid. Consequently, during reflow, the specific keto acid volatilizes together with the solvent that has already started to volatilize. As a result, during reflow, the bubbles (voids) formed by the volatilization of the solvent and the specific keto acid fuse together and grow larger, making it easier for the voids to be discharged from the solder paste. In other words, it becomes easier to suppress the occurrence of voids during reflow.

[0057] Tk is preferably 280°C or lower, more preferably 270°C or lower, even more preferably 260°C or lower, and particularly preferably 250°C or lower. As Tk is lower than the upper limit mentioned above, the specific keto acid becomes more likely to volatilize along with the solvent during reflow. Consequently, during reflow, the voids formed by the volatilization of the solvent and the specific keto acid fuse together and grow larger, making it easier for the voids to be discharged from the solder paste. In other words, it becomes easier to suppress the occurrence of voids during reflow.

[0058] Tk is preferably 150°C or higher and 280°C or lower, more preferably 200°C or higher and 270°C or lower, even more preferably 220°C or higher and 260°C or lower, and particularly preferably 230°C or higher and 250°C or lower.

[0059] Other Keto Acids

[0060] The water-soluble flux according to the present embodiment may contain, as other keto acids, a keto acid having a melting point greater than 40°C.

[0061] Other keto acids include, for example, oxaloacetate (melting point: 161°C), α-ketoglutaric acid (melting point: 113.5°C), acetone dicarboxylic acid (melting point: 138°C), α-ketoadipoic acid (melting point: 127°C), β-ketoadipoic acid (melting point: 124-126°C), etc.

[0062] Other keto acids may be used as a single type or as a mixture of two or more types.

[0063] The content of a specific keto acid in the above flux is preferably 5 mass% or more with respect to the total amount (100 mass%) of the above flux, more preferably 10 mass% or more, and even more preferably 15 mass% or more. In addition, the content is preferably 30 mass% or less, more preferably 25 mass% or less, and more preferably 20 mass% or less.

[0064] For example, the content of a specific keto acid in the above flux may be 10 mass% or more and 25 mass% or less with respect to the total amount (100 mass%) of the above flux, 15 mass% or more and 25 mass% or less, or 15 mass% or more and 20 mass% or less.

[0065] The content of a specific keto acid in the above flux is preferably 90 mass% or more with respect to the total mass (100 mass%) of the keto acid, and more preferably 100 mass%.

[0066] By ensuring that the content of a specific keto acid is above the above lower limit, it becomes easier to suppress the occurrence of voids. By ensuring that the content of a specific keto acid is below the above upper limit, it becomes easier to increase the stability of the flux over time during storage.

[0067] Solvent

[0068] Specific Solvents

[0069] The water-soluble flux according to the present embodiment contains a specific solvent (S1) having a boiling point of 240°C or lower. The lower limit of the boiling point of the specific solvent is not specifically limited, but, for example, it may be 150°C or higher.

[0070] Specific solvents include, for example, water, glycol ether-based solvents with a boiling point of 240°C or lower, terpineols with a boiling point of 240°C or lower, alcohol-based solvents with a boiling point of 240°C or lower, ester-based solvents with a boiling point of 240°C or lower.

[0071] Examples of glycol ether-based solvents with a boiling point of 240°C or lower include phenyl glycol (boiling point 237°C: ethylene glycol monophenyl ether), butyl galbitol (boiling point 231°C: diethylene glycol monobutyl ether), and hexylene glycol (boiling point 197°C: 2-methylpentane-2,4-diol).

[0072] boiling point Examples of terpineols with a boiling point of 240°C or lower include α-terpineol (boiling point 217°C).

[0073] Examples of alcohol-based solvents with a boiling point of 240°C or lower include ethanol (boiling point 78°C), 1-propanol (boiling point 97°C), 2-propanol (boiling point 82°C), 1,2-butanediol (boiling point 192°C), 2,2-dimethyl-1,3-propanediol (boiling point 210°C), 2,5-dimethyl-2,5-hexanediol (boiling point 215°C), 2,5-dimethyl-3-hexine-2,5-diol (boiling point 206°C), 2,3-dimethyl-2,3-butanediol (boiling point 174°C), 2-methylpentane-2,4-diol (boiling point 197°C), 1-ethynyl-1-cyclohexanol (boiling point 180°C), etc.

[0074] Specific solvents may be used as a single type or as a mixture of two or more types.

[0075] It is preferable that the specific solvent comprises one or more selected from the group consisting of glycol ether-based solvents with a boiling point of 240°C or lower, terpineols with a boiling point of 240°C or lower, alcohol-based solvents with a boiling point of 240°C or lower, and ester-based solvents with a boiling point of 240°C or lower, and it is more preferable that the specific solvent comprises one or more selected from the group consisting of glycol ether-based solvents with a boiling point of 240°C or lower and terpineols with a boiling point of 240°C or lower.

[0076] It is more preferable that the specific solvent comprises one or more selected from the group consisting of phenyl glycol, hexylene glycol, and α-terpineol, and it is even more preferable that it comprises α-terpineol.

[0077] The boiling point (Ts) of a specific solvent is preferably 150°C or higher, more preferably 180°C or higher, even more preferably 190°C or higher, particularly preferably 200°C or higher, and most preferably 210°C or higher. By having Ts above the lower limit, it becomes easier to suppress the occurrence of voids.

[0078] Ts is 240°C or lower, preferably 235°C or lower, more preferably 230°C or lower, and even more preferably 225°C or lower. By keeping Ts below the upper limit, it becomes easier to suppress the occurrence of voids.

[0079] Ts is preferably 150°C or higher and 240°C or lower, more preferably 180°C or higher and 235°C or lower, even more preferably 200°C or higher and 230°C or lower, and particularly preferably 210°C or higher and 225°C or lower.

[0080] The absolute value of the temperature difference (△T) between Tk and Ts is preferably 0°C or higher, more preferably 3°C or higher, and even more preferably 5°C or higher.

[0081] As △T is greater than the above lower limit, it becomes easier to suppress the occurrence of voids.

[0082] △T is preferably 70℃ or lower, more preferably 60℃ or lower, and even more preferably 55℃ or lower.

[0083] Since △T is below the upper limit mentioned above, it becomes easier to suppress the occurrence of voids.

[0084] Additionally, Tk and Ts are, Ts <Tk의 관계를 만족시키는 것이 바람직하다.

[0085] Ts <Tk인 경우, △T는, 5℃ 이상 50℃ 이하인 것이 바람직하고, 10℃ 이상 45℃ 이하인 것이 보다 바람직하고, 15℃ 이상 40℃ 이하인 것이 더욱 바람직하고, 20℃ 이상 35℃ 이하인 것이 특히 바람직하다.

[0086] By ensuring that △T is within the above range, it becomes easier to suppress the occurrence of voids.

[0087] Other Solvents

[0088] The water-soluble flux according to the present embodiment may contain other solvents (i.e., solvents other than specific solvents).

[0089] Other solvents include, for example, glycol ether-based solvents with a boiling point greater than 240°C, alcohol-based solvents with a boiling point greater than 240°C, ester-based solvents with a boiling point greater than 240°C, etc.

[0090] Examples of glycol ether-based solvents with a boiling point greater than 240°C include diethylene glycol monohexyl ether (boiling point 258°C), diethylene glycol mono-2-ethylhexyl ether (boiling point 272°C), diethylene glycol dibutyl ether (boiling point 256°C), triethylene glycol monobutyl ether (boiling point 278°C), triethylene glycol butyl methyl ether (boiling point 261°C), tetraethylene glycol dimethyl ether (boiling point 275°C), tripropylene glycol monomethyl ether (boiling point 243°C), etc.

[0091] As alcohol-based solvents with a boiling point exceeding 240°C, for example, 2,4-diethyl-1,5-pentanediol (boiling point 264°C), 2-ethyl-2-hydroxymethyl-1,3-propanediol (boiling point 292°C), 2,2'-oxybis(methylene)bis(2-ethyl-1,3-propanediol) (boiling point 448°C), 1,2,6-trihydroxyhexane (boiling point 386°C), 1,4-cyclohexanediol (boiling point 293°C), 1,4-cyclohexanedimethanol (boiling point 283°C), 2,4,7,9-tetramethyl-5-decine-4,7-diol (boiling point 255°C), 2,2-bis(hydroxymethyl)-1,3-propanediol (boiling point 437°C), Examples include isobornylcyclohexanol (boiling point 318°C).

[0092] Examples of ester-based solvents with a boiling point exceeding 240°C include bis(2-ethylhexyl) sebacate (boiling point 377°C).

[0093] Other solvents may be used as a single type or as a mixture of two or more types.

[0094] The content of a specific solvent in the above flux is preferably 10 mass% or more and 70 mass% or less with respect to the total amount (100 mass%) of the above flux, more preferably 15 mass% or more and 60 mass% or less, and even more preferably 15 mass% or more and 50 mass% or less.

[0095] The content of a specific solvent in the above flux is preferably 90 mass% or more with respect to the total mass (100 mass%) of the solvent, and more preferably 100 mass%.

[0096] By ensuring that the content of a specific solvent is above the above lower limit, it becomes easier to suppress the occurrence of voids.

[0097] The mixing ratio of a specific keto acid and a specific solvent is a mass ratio expressed as specific solvent / specific keto acid, that is, the ratio of the content of the specific solvent to the content of the specific keto acid, preferably 0.60 to 4.0, more preferably 0.60 to 3.0, and even more preferably 0.60 to 2.5.

[0098] If this mixing ratio is within the above-mentioned desirable range, it becomes easier to suppress the occurrence of voids.

[0099] Other ingredients

[0100] The flux in this embodiment may include other components as needed, in addition to the keto acid and solvent.

[0101] Other ingredients may include organic acids other than keto acids, other active agents such as amines and halogen compounds, surfactants, metal inactivators, silane coupling agents, antioxidants, coloring agents, etc.

[0102] [Organic acids other than keto acids]

[0103] Examples of organic acids other than keto acids include carboxylic acids and organic sulfonic acids.

[0104] Examples of carboxylic acids include aliphatic carboxylic acids and aromatic carboxylic acids.

[0105] As carboxylic acids, for example, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, eicosan-2 acid, salicylic acid, dipicoric acid, dibutyraniline diglycolic acid, suberic acid, sebacic acid, terephthalic acid, dodecane-2 acid, parahydroxyphenylacetic acid, picolinic acid, phenyl succinic acid, phthalic acid, lauric acid, benzoic acid, tartaric acid, isocyanurate tris(2-carboxyethyl), 1,3-cyclohexanedicarboxylic acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butanoic acid, 2,3-dihydroxybenzoic acid, 2,4-diethyl glutaric acid, 2-quinoline carboxylic acid, 3-hydroxybenzoic acid, p-anisic acid, Stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, myristic acid, palmitic acid, pimeric acid, caproic acid, enantic acid, caprylic acid, pelargonic acid, isoperargonic acid, capric acid, caproreinic acid, undecanic acid, lauric acid, linderic acid, tridecanoic acid, myristoleic acid, pentadecanic acid, isopalmitic acid, palmitoleic acid, hiragonic acid, hydronocapinic acid, margaric acid, isostearic acid, elaidic acid, petroseric acid, moroctic acid, eleostearic acid, tariric acid, vaxenic acid, liminooleic acid, bernoic acid, sterculic acid, nonadecanic acid, eicosanic acid, dimer acid, trimer acid, hydrogenated dimer acid which is a hydrogenated product of dimer acid, hydrogen added to trimer acid Examples of added hydrogenated products include hydrogenated trimeric acid.

[0106] As for dimer acid and trimer acid, for example, dimer acid that is the reactant of oleic acid and linoleic acid, trimer acid that is the reactant of oleic acid and linoleic acid, dimer acid that is the reactant of acrylic acid, trimer acid that is the reactant of acrylic acid, dimer acid that is the reactant of methacrylic acid, trimer acid that is the reactant of methacrylic acid, dimer acid that is the reactant of acrylic acid and methacrylic acid, trimer acid that is the reactant of acrylic acid and methacrylic acid, dimer acid that is the reactant of oleic acid, trimer acid that is the reactant of oleic acid, dimer acid that is the reactant of linoleic acid, trimer acid that is the reactant of linoleic acid, dimer acid that is the reactant of linolenic acid, trimer acid that is the reactant of linolenic acid, dimer acid that is the reactant of acrylic acid and oleic acid, trimer acid that is the reactant of acrylic acid and linoleic acid, dimer acid that is the reactant of acrylic acid and linoleic acid, trimer acid that is the reactant of acrylic acid and linoleic acid, acrylic acid and Examples include dimer acid that is a reaction product of linolenic acid, trimer acid that is a reaction product of acrylic acid and linolenic acid, dimer acid that is a reaction product of methacrylic acid and oleic acid, trimer acid that is a reaction product of methacrylic acid and oleic acid, dimer acid that is a reaction product of methacrylic acid and linoleic acid, trimer acid that is a reaction product of methacrylic acid and linolenic acid, trimer acid that is a reaction product of methacrylic acid and linolenic acid, dimer acid that is a reaction product of oleic acid and linolenic acid, trimer acid that is a reaction product of oleic acid and linolenic acid, dimer acid that is a reaction product of linoleic acid and linolenic acid, trimer acid that is a reaction product of linoleic acid and linolenic acid, hydrogenated dimer acid that is a hydrogenated product of each of the above-mentioned dimer acids, and hydrogenated trimer acid that is a hydrogenated product of each of the above-mentioned trimer acids.

[0107] For example, dimer acid, which is the reaction product of oleic acid and linoleic acid, is a dimer with 36 carbon atoms. Also, trimer acid, which is the reaction product of oleic acid and linoleic acid, is a trimer with 54 carbon atoms.

[0108] Examples of organic sulfonic acids include aliphatic sulfonic acids and aromatic sulfonic acids. Examples of aliphatic sulfonic acids include alkane sulfonic acids and alkanol sulfonic acids.

[0109] Examples of alkanes include methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, 2-propanesulfonic acid, 1-butanesulfonic acid, 2-butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid, decanesulfonic acid, dodecanesulfonic acid, etc.

[0110] Examples of alkanol sulfonic acids include, for instance, 2-hydroxyethane-1-sulfonic acid, 2-hydroxypropane-1-sulfonic acid, 2-hydroxybutane-1-sulfonic acid, 2-hydroxypentane-1-sulfonic acid, 1-hydroxypropane-2-sulfonic acid, 3-hydroxypropane-1-sulfonic acid, 4-hydroxybutane-1-sulfonic acid, 2-hydroxyhexane-1-sulfonic acid, 2-hydroxydecane-1-sulfonic acid, and 2-hydroxydodecane-1-sulfonic acid.

[0111] Examples of aromatic sulfonic acids include 1-naphthalene sulfonic acid, 2-naphthalene sulfonic acid, p-toluene sulfonic acid, xylene sulfonic acid, p-phenol sulfonic acid, cresol sulfonic acid, sulfosalicylic acid, nitrobenzene sulfonic acid, sulfobenzoic acid, and diphenylamine-4-sulfonic acid.

[0112] Organic acids other than keto acids may be used as a single type or as a mixture of two or more types.

[0113] It is preferable that organic acids other than keto acids include one or more selected from the group consisting of carboxylic acids and organic sulfonic acids. It is preferable that the carboxylic acid includes an aliphatic dicarboxylic acid, and more preferable that it includes glutaric acid. It is preferable that the organic sulfonic acid includes an aromatic sulfonic acid, and more preferable that it includes p-toluenesulfonic acid.

[0114] The content of organic acids other than keto acids in the above flux is preferably 1 mass% or more and 10 mass% or less with respect to the total mass (100 mass%) of the flux, and more preferably 2 mass% or more and 6 mass% or less.

[0115] The content of a specific keto acid in the above flux is preferably 75 mass% or more with respect to the total mass (100 mass%) of the organic acid, more preferably 80 mass% or more, and even more preferably 85 mass% or more. The upper limit of the content of the specific keto acid is not particularly limited, but it may be 100 mass%.

[0116] By ensuring that the content of specific keto acids is above the above lower limit, it becomes easier to suppress the occurrence of voids.

[0117] [Amine]

[0118] Examples of amines include azoles, guanidines, alkyl amine compounds, amino alcohol compounds, amine polyoxyalkylene adducts, etc.

[0119] As azoles, for example, 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-undecylimidazolium trimeritate, 1-cyanoethyl-2-phenylimidazolium trimeritate, 2,4-diamino-6-[2'-methylimidazoleyl(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazoleyl(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazoleyl(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazoleyl(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-methylimidazole, 2-phenylimidazole, 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'-methylene bis[6-(2H-benzotriazole-2-yl)-4-tert-octylphenol],6-(2-benzotriazoleyl)-4-tert-octyl-6´-tert-butyl-4'-methyl-2,2'-methylene bisphenol, 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-benzotriazole-1-yl)methyl]imino]bisethanol, 1-(1´,2'-dicarboxyethyl)benzotriazole, 1-(2,3-dicarboxypropyl)benzotriazole, 1-[(2-ethylhexylamino)methyl]benzotriazole, 2,6-bis[(1H-benzotriazole-1-yl) Examples include methyl]-4-methylphenol, 5-methylbenzotriazole, 5-phenyltetrazole, etc.

[0120] Examples of guanidines include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, 1,3-di-o-coumenylguanidine, 1,3-di-o-coumenyl 2-propionylguanidine, etc.

[0121] Examples of alkyl amine compounds include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, stearylamine, etc.

[0122] Examples of amino alcohol compounds include monoisopropanolamine.

[0123] Examples of amine polyoxyalkylene adducts include terminal diamine polyalkylene glycol, aliphatic amine polyoxyalkylene adduct, aromatic amine polyoxyalkylene adduct, polyvalent amine polyoxyalkylene adduct, etc.

[0124] Examples of alkylene oxides from which amine polyoxyalkylene adducts originate include ethylene oxide, propylene oxide, butylene oxide, etc.

[0125] Terminal diamine polyalkylene glycol is a compound in which both ends of polyalkylene glycol are aminated.

[0126] Examples of terminal diamine polyalkylene glycols include terminal diamine polyethylene glycol, terminal diamine polypropylene glycol, and terminal diamine polyethylene glycol-polypropylene glycol copolymer.

[0127] Examples of terminal diamine polyethylene glycol-polypropylene glycol copolymers include polyethylene glycol-polypropylene glycol copolymer bis(2-aminopropyl) ether and polyethylene glycol-polypropylene glycol copolymer bis(2-aminoethyl) ether.

[0128] Aliphatic amine polyoxyalkylene adducts, aromatic amine polyoxyalkylene adducts, and polyvalent amine polyoxyalkylene adducts are formed by a polyoxyalkylene group being bonded to the nitrogen atom of an amine. Examples of the above amines include ethylene diamine, 1,3-propane diamine, 1,4-butane diamine, hexamethylene diamine, lauryl amine, stearyl amine, oleyl amine, beef tallow amine, hydrogenated beef tallow amine, beef tallow propyl diamine, m-xylene diamine, diethylene triamine, metaxylene diamine, tolylene diamine, paraxylene diamine, phenylene diamine, isophorone diamine, 1,10-decane diamine, 1,12-dodecane diamine, 4,4-diamino dicyclohexyl methane, 4,4-diamino diphenyl methane, butane-1,1,4,4-tetraamine, pyrimidine-2,4,5,6-tetraamine, etc.

[0129] Examples of aliphatic amine polyoxyalkylene adducts include polyoxyalkylene alkylamines. Examples of polyoxyalkylene alkylamines include polyoxyalkylene ethylenediamine. Polyoxyalkylene ethylenediamine is one in which at least one polyoxyalkylene group is bonded to any one of the nitrogen atoms of ethylenediamine. Examples of polyoxyalkylene ethylenediamines include polyoxyethylene ethylenediamine, polyoxypropylene ethylenediamine, and polyoxyethylene polyoxypropylene ethylenediamine. Polyoxyethylene ethylenediamine is one in which one or more polyoxyethylene groups are bonded to any one of the nitrogen atoms of ethylenediamine, and polyoxypropylene ethylenediamine is one in which one or more polyoxypropylene groups are bonded to any one of the nitrogen atoms of ethylenediamine. Polyoxyethylene polyoxypropylene ethylenediamine is one in which at least one polyoxypropylene group or polyoxyethylene group is bonded to any one of the nitrogen atoms of ethylenediamine.

[0130] Examples of polyoxyalkylene ethylene diamines include N-polyoxypropylene ethylene diamine, N-polyoxyethylene ethylene diamine, N-polyoxyethylene polyoxypropylene ethylene diamine, N,N,N',N'-tetrakis(2-hydroxyethyl) ethylene diamine, N,N,N',N'-tetrakis(2-hydroxypropyl) ethylene diamine, etc.

[0131] One type of amine may be used alone, or two or more types may be used in combination.

[0132] It is preferable that the amine comprises one or more selected from the group consisting of azoles, alkyl amine compounds, and amine polyoxyalkylene adducts.

[0133] It is preferable that the azoles include 2-ethylimidazole.

[0134] The alkyl amine compound preferably includes triethylenetetramine.

[0135] It is preferable that the amine polyoxyalkylene adduct comprises a terminal diamine polyalkylene glycol and / or an aliphatic amine polyoxyalkylene adduct.

[0136] As an aliphatic amine polyoxyalkylene adduct, it is preferable to include polyoxyalkylene ethylenediamine, and more preferable to include N,N,N',N'-tetrakis(2-hydroxypropyl) ethylenediamine.

[0137] As for the terminal diamine polyalkylene glycol, it is preferable to include a terminal diamine polyethylene glycol-polypropylene glycol copolymer.

[0138] The total content of azoles and alkyl amine compounds is preferably 0.5 mass% or more and 6 mass% or less with respect to the total mass (100 mass%) of the flux, and more preferably 1 mass% or more and 4 mass% or less.

[0139] The content of the aliphatic amine polyoxyalkylene adduct is preferably 10 mass% or more and 40 mass% or less with respect to the total mass (100 mass%) of the flux, and more preferably 15 mass% or more and 30 mass% or less.

[0140] [Halogen Compounds]

[0141] Examples of halogen-based active agents include amine hydrohalides, organic halogen compounds other than amine hydrohalides, etc.

[0142] Amine hydrohalides are compounds formed by reacting an amine with a hydrogen halide.

[0143] Examples of amines here include aliphatic amines, azoles, guanidines, etc. Examples of hydrogen halides include hydrides of chlorine, bromine, and iodine.

[0144] Examples of aliphatic amines include ethylamine, diethylamine, triethylamine, ethylenediamine, etc. Examples of guanidines and azoles include the amines mentioned above.

[0145] More specifically, as amine hydrohalides, for example, 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, dimethylamine hydrochloride, rosinamine hydrobromide, 2-ethylhexylamine hydrochloride, isopropylamine hydrochloride, cyclohexylamine hydrochloride, 2-pipecholine hydrobromide, 1,3-diphenylguanidine hydrochloride, dimethylbenzylamine hydrochloride, hydrazine hydrochloride, dimethylcyclohexylamine Hydrochloride, Trinonylamine Hydrobromide, Diethylaniline Hydrobromide, 2-Diethylaminoethanol Hydrobromide, 2-Diethylaminoethanol Hydrochloride, Ammonium Chloride, Diallylamine Hydrochloride, Diallylamine 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-Phenimidazole Hydrobromide, 4-Benzylpyridine Hydrobromide, L-Glutamic Acid Examples include hydrochloride, N-methylmorpholine hydrochloride, betaine hydrochloride, 2-pipecholine hydroiodide, cyclohexylamine hydroiodide, 1,3-diphenylguanidine hydrofluoride, diethylamine hydrofluoride, 2-ethylhexylamine hydrofluoride, cyclohexylamine hydrofluoride, ethylamine hydrofluoride, rosinamine hydrofluoride, cyclohexylamine tetrafluoroborate, and dicyclohexylamine tetrafluoroborate.

[0146] In addition, as halogen compounds, for example, a salt formed by reacting an amine with tetrafluoroboric acid (HBF4) and a complex formed by reacting an amine with boron trifluoride (BF3) can also be used.

[0147] Examples of the above complexes include piperidine trifluoride.

[0148] Examples of organic halogen compounds other than amine hydrohalides include halogenated aliphatic compounds. A halogenated aliphatic hydrocarbon group refers to a hydrocarbon group in which some or all of the hydrogen atoms constituting the aliphatic hydrocarbon group are substituted with halogen atoms.

[0149] Examples of halogenated aliphatic compounds include halogenated aliphatic alcohols and halogenated heterocyclic compounds.

[0150] 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, trans-2,3-dibromo-2-butene-1,4-diol.

[0151] Examples of heterocyclic halogenated compounds include compounds represented by the following general formula (2).

[0152] R 21 -(R 22 ) n (2)

[0153] [In the middle of the meal, R 21 represents a complex expression of value n. R 22 represents a halogenated aliphatic hydrocarbon group.

[0154] R 21In the above, as the complex ring of the n-valent complex ring group, a ring structure in which some of the carbon atoms constituting an aliphatic hydrocarbon or aromatic hydrocarbon ring are substituted with heteroatoms can be cited. Examples of heteroatoms in this complex ring include oxygen atoms, sulfur atoms, nitrogen atoms, etc. This complex ring is preferably a 3 to 10-membered ring, and more preferably a 5 to 7-membered ring. Examples of this complex ring include an isocyanurate ring, etc.

[0155] R 22 In the above, the halogenated aliphatic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably 3 to 5 carbon atoms. In addition, R 22 Brominated aliphatic hydrocarbon groups and chlorinated aliphatic hydrocarbon groups are preferred, brominated aliphatic hydrocarbon groups are more preferred, and brominated saturated aliphatic hydrocarbon groups are even more preferred.

[0156] Examples of heterocyclic halogenated compounds include tris(2,3-dibromopropyl) isocyanurate.

[0157] In addition, organic halogen compounds other than amine hydrohalides include, for example, iodinated carboxyl compounds such as 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, 5-iodoanthranilic acid; chloride carboxyl compounds such as 2-chlorobenzoic acid, 3-chloropropionic acid; and brominated carboxyl compounds such as 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid, 2-bromobenzoic acid.

[0158] Halogen compounds may be used as a single type or as a mixture of two or more types.

[0159] Surfactants

[0160] Examples of surfactants include nonionic surfactants.

[0161] Examples of nonionic surfactants include polyalkylene glycols.

[0162] Examples of alkylene oxides from which polyalkylene glycols originate include ethylene oxide, propylene oxide, butylene oxide, etc.

[0163] Examples of polyalkylene glycols include polyethylene glycol, ethylene oxide-resorcinol copolymer, polyoxyalkylene acetylene glycols, polyoxyalkylene glyceryl ether, polyoxyalkylene alkyl ether, polyoxyalkylene ester, polyoxyalkylene alkyl amide, etc.

[0164] Alternatively, as a nonionic surfactant, polyoxyalkylene adducts of alcohols may be used. Examples of the above alcohols include aliphatic alcohols, aromatic alcohols, and polyhydric alcohols.

[0165] Surfactants may be used as a single type or as a mixture of two or more types.

[0166] The water-soluble flux according to the present embodiment preferably contains a surfactant.

[0167] It is preferable that the surfactant includes a nonionic surfactant, and it is more preferable that it includes one or more selected from the group consisting of ethylene oxide-resorcinol copolymers and aliphatic alcohol polyoxyalkylene adducts.

[0168] The content of the surfactant is preferably 5 mass% or more and 75 mass% or less with respect to the total mass (100 mass%) of the flux, more preferably 5 mass% or more and 65 mass% or less, and more preferably 5 mass% or more and 30 mass% or less.

[0169] Metal Inerts

[0170] Examples of metal inerts include hindered phenolic compounds and nitrogen compounds.

[0171] The term "metal inert" used here refers to a compound that has the ability to prevent metal from deteriorating upon contact with a certain type of compound.

[0172] Hindered phenolic compounds refer to phenolic compounds having a bulky substituent (e.g., a branched or cyclic alkyl group such as a t-butyl group) at least one side of the ortho-position of phenol.

[0173] Hindered phenolic compounds are not particularly limited, and examples include bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylene bis(oxyethylene)], N,N'-hexamethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionat], 2,2'-methylene bis[6-(1-methylcyclohexyl)-p-cresol], 2,2'-methylene bis(6-tert-butyl-p-cresol), and 2,2'-methylene bis(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-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, pentaerythrityl tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2-thio-diethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, Examples include N,N'-hexamethylene bis(3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 3,5-di-tert-butyl-4-hydroxybenzyl phosphonato-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 general formula (3).

[0174]

[0175] (In the formula, Z is an alkylene group that may be substituted. R 101 and R 102 is, each independently, an alkyl group, aralkyl group, aryl group, heteroaryl group, cycloalkyl group, or heterocycloalkyl group that may be substituted.103 and R 104 is an alkyl group that may be substituted, each independently.

[0176] Examples of nitrogen compounds in metal inerts include hydrazide-based nitrogen compounds, amide-based nitrogen compounds, triazole-based nitrogen compounds, melamine-based nitrogen compounds, etc.

[0177] As for the hydrazide nitrogen compounds, any nitrogen compound having a hydrazide skeleton is sufficient, such as dodecane dioxide bis[N2-(2-hydroxybenzoyl)hydrazide], N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, decanedicarboxylic acid disalisilyl hydrazide, N-salicylidene-N'-salicyl hydrazide, m-nitrobenz hydrazide, 3-aminophthal hydrazide, phthalate dihydrazide, adipic acid hydrazide, oxarobis(2-hydroxy-5-octylbenzylidene hydrazide), N'-benzoylpyrrolidone carboxylic acid hydrazide, Examples include N,N'-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl) hydrazine.

[0178] As for amide-type nitrogen compounds, any nitrogen compound having an amide skeleton can be used, such as N,N'-bis{2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxyl]ethyl}oxamide.

[0179] As for triazole nitrogen compounds, any nitrogen compound having a triazole skeleton can be used, such as N-(2H-1,2,4-triazole-5-yl) salicylamide, 3-amino-1,2,4-triazole, 3-(N-salisilyl)amino-1,2,4-triazole, etc.

[0180] Melamine-based nitrogen compounds can be nitrogen compounds having a melamine skeleton, such as melamine and melamine derivatives. More specifically, examples include trisaminotriazine, alkylated trisaminotriazine, alkoxyalkylated trisaminotriazine, melamine, alkylated melamine, alkoxyalkylated melamine, N2-butyl melamine, N2,N2-diethyl melamine, N,N,N',N',N'',N''-hexakis(methoxymethyl) melamine.

[0181] Metal inerts may be used as a single type or as a mixture of two or more types.

[0182] It is preferable that the flux according to the present embodiment does not contain a resin component. In the present specification, examples of resin components include rosin, resins other than rosin, etc.

[0183] In this specification, "rosin" includes a natural resin comprising a mixture of abietic acid and its isomers, with abietic acid as the main component, and a chemically modified natural resin (which may be referred to as a rosin derivative).

[0184] The abietic acid content in the natural resin is, for example, 40 mass% or more and 80 mass% or less with respect to the natural resin.

[0185] In this specification, "main component" refers to a component among the components constituting a compound that has a content of 40 mass% or more in the compound.

[0186] Representative isomers of abietic acid include neobietic acid, palustric acid, and levopimaric acid. The structure of abietic acid is shown below.

[0187]

[0188] Examples of the above “natural resins” include gum rosin, wood rosin, and tall oil rosin.

[0189] In the present invention, "a chemically modified natural resin (rosin derivative)" includes one or more treatments selected from the group consisting of hydrogenation, dehydrogenation, neutralization, alkylene oxide addition, amidation, dimerization and polymerization, esterification, and Diels-Alder cyclization addition to the "natural resin."

[0190] Examples of rosin derivatives include purified rosin and modified rosin.

[0191] Examples of modified rosin include, for instance, hydrogenated rosin, polymerized hydrogenated rosin, disproportionated rosin, acid-modified rosin, rosin ester, acid-modified hydrogenated rosin, hydrochloric acid-modified hydrogenated rosin, acid-modified disproportionated rosin, hydrochloric acid-modified disproportionated rosin, phenol-modified rosin and α,β-unsaturated carboxylic acid modified products (acrylic acid-modified rosin, maleic acid-modified rosin, fumaric acid-modified rosin, etc.), and purified products, hydrides, and disproportions of the above-mentioned polymerized rosin, and purified products, hydrides, and disproportions of the above-mentioned α,β-unsaturated carboxylic acid modified products, rosin alcohol, rosin amine, hydrogenated rosin alcohol, rosin ester, hydrogenated rosin ester, rosin soap, hydrogenated rosin soap, acid-modified rosin soap, etc.

[0192] Examples of rosin amines include dehydroabiethylamine and dihydroabiethylamine. Rosin amine refers to so-called disproportionate rosin amine. The respective structures of dehydroabiethylamine and dihydroabiethylamine are shown below.

[0193]

[0194] Examples of resins other than rosin include terpene resin, modified terpene resin, terpene phenol resin, modified terpene phenol resin, styrene resin, modified styrene resin, xylene resin, modified xylene resin, acrylic resin, polyethylene resin, acrylic-polyethylene copolymer resin, and other thermosetting resins.

[0195] Examples of modified terpene resins include aromatic modified terpene resins, hydrogenated terpene resins, and hydrogenated aromatic modified terpene resins. Examples of modified terpene phenol resins include hydrogenated terpene phenol resins. Examples of modified styrene resins include styrene acrylic resins and styrene maleic acid resins. Examples of modified xylene resins include phenol modified xylene resins, alkyl phenol modified xylene resins, phenol modified resor-type xylene resins, polyol modified xylene resins, and polyoxyethylene added xylene resins.

[0196] Other thermosetting resins include, for example, epoxy resin.

[0197] Examples of epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, glycidylamine type resin, alicyclic epoxy resin, aminopropane type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, anthracene type epoxy resin, triazine type epoxy resin, dicyclopentadiene type epoxy resin, triphenylmethane type epoxy resin, fluorene type epoxy resin, phenol aralkyl type epoxy resin, novolak type epoxy resin, etc.

[0198] The flux according to the present embodiment is more suitable as a water-soluble flux by not containing at least one resin component selected from the group consisting of rosin and thermosetting resin.

[0199] The water-soluble flux according to the present embodiment described above contains a combination of a keto acid having a melting point of 40°C or lower and a solvent having a boiling point of 240°C or lower, thereby making it possible to further suppress the occurrence of voids during reflow (reflow temperature, for example, 180 to 300°C). Although the reason for obtaining this effect is not certain, it is presumed as follows.

[0200] Organic acids, such as dicarboxylic acids commonly used as activators, typically have a melting point of around 100°C or higher. In contrast, the specific keto acid in the water-soluble flux according to the present embodiment has a melting point of 40°C or lower. By containing the specific keto acid in the water-soluble flux according to the present embodiment, the fluidity of the solder paste is increased during reflow. In addition, since the specific solvent in the water-soluble flux according to the present embodiment has a boiling point of 240°C or lower, it is prone to volatilizing during reflow and generating bubbles (voids). It is presumed that due to the synergistic effect of these, the voids generated in the solder paste fuse together and grow larger, making it easier for the voids to be discharged from the solder paste.

[0201] Additionally, it is speculated that if the boiling point of a specific keto acid is 250°C or lower, the specific keto acid can volatilize along with the solvent, making it easier for voids to be discharged from the solder paste.

[0202] (Solder paste)

[0203] The solder paste of the present embodiment contains solder alloy powder and the flux described above.

[0204] The solder alloy powder may be composed of a powder of solder of Sn as a single element, or a powder of a solder alloy such as Sn-Ag, Sn-Cu, Sn-Ag-Cu, Sn-Bi, Sn-In, etc., or a powder of a solder alloy to which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. are added.

[0205] The solder alloy powder may be composed of a Sn-Pb-based solder alloy, or a solder alloy powder to which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. are added.

[0206] It is preferable that the solder alloy powder be a solder that does not contain Pb.

[0207] As for the solder alloy powder, for example, one having a melting temperature of 150 to 250°C can be used.

[0208] Flux content:

[0209] In the solder paste, the flux content is preferably 5 to 30 mass% with respect to the total mass of the solder paste, and more preferably 5 to 15 mass%.

[0210] The solder paste according to the present embodiment can further suppress the occurrence of voids by containing a flux comprising a keto acid having a melting point of 40°C or lower and a solvent having a boiling point of 240°C or lower.

[0211] As described above, in the solder paste according to the present embodiment, it is presumed that voids are easily discharged from the solder paste by volatilizing a specific keto acid and a specific solvent during reflow. The following may be cited as the composition of the flux that facilitates the discharge of voids from the solder paste.

[0212] That is, the above flux contains a specific keto acid and a specific solvent, and it is preferable that the boiling point (Tk) of the specific keto acid and the boiling point (Ts) of the specific solvent satisfy the following conditions.

[0213] Tk is preferably 150°C or higher and 280°C or lower, more preferably 200°C or higher and 270°C or lower, even more preferably 220°C or higher and 260°C or lower, and particularly preferably 230°C or higher and 250°C or lower.

[0214] Ts is preferably 150°C or higher and 240°C or lower, more preferably 180°C or higher and 235°C or lower, even more preferably 200°C or higher and 230°C or lower, and particularly preferably 210°C or higher and 225°C or lower.

[0215] The absolute value of the temperature difference (△T) between Tk and Ts is preferably 0°C or higher, more preferably 3°C or higher, and even more preferably 5°C or higher.

[0216] As △T is greater than the above lower limit, it becomes easier to suppress the occurrence of voids.

[0217] △T is preferably 70℃ or lower, more preferably 60℃ or lower, and even more preferably 55℃ or lower.

[0218] Since △T is below the upper limit mentioned above, it becomes easier to suppress the occurrence of voids.

[0219] The content of a specific keto acid in the above flux may be 10 mass% or more and 25 mass% or less with respect to the total amount (100 mass%) of the above flux, 15 mass% or more and 25 mass% or less, or 15 mass% or more and 20 mass% or less.

[0220] The content of a specific solvent in the above flux is preferably 10 mass% or more and 70 mass% or less with respect to the total amount (100 mass%) of the above flux, and more preferably 15 mass% or more and 60 mass% or less.

[0221] Additionally, Tk and Ts are, Ts <Tk의 관계를 만족시키는 것이 바람직하다.

[0222] When this relationship is satisfied, when the reflow temperature reaches the solder melting temperature, a specific keto acid volatilizes along with a specific solvent that has already started to volatilize. As a result, voids are more easily discharged from the solder paste.

[0223] Ts <Tk인 경우, △T는, 5℃ 이상 50℃ 이하인 것이 바람직하고, 10℃ 이상 45℃ 이하인 것이 보다 바람직하고, 15℃ 이상 40℃ 이하인 것이 더욱 바람직하고, 20℃ 이상 35℃ 이하인 것이 특히 바람직하다.

[0224] By ensuring that △T is within the above range, it becomes easier to suppress the occurrence of voids.

[0225] [Example]

[0226] The present invention will be explained below by way of examples, but the present invention is not limited to the following examples.

[0227] Josee of Flux

[0228] (Examples 1–9, Comparative Examples 1–4)

[0229] Each flux of the examples and comparative examples was prepared with the compositions shown in Tables 1 and 2.

[0230] The raw materials used are shown below.

[0231] The melting point value of the compound used in the example is the value listed in the "Chemical Handbook Basic Volume, 5th Edition (Japan Chemical Society, Maruzen Publishing)." The boiling point value of the compound used in the example is the value obtained by measuring the temperature of the liquid when the saturated vapor pressure of the liquid becomes equal to 1 atmosphere (i.e., 1013 hPa).

[0232] Specific keto acids:

[0233] Levulinic acid (melting point: 37.2℃, boiling point: 245℃), pyruvate (melting point: 13.6℃, ​​boiling point: 165℃),

[0234] Other keto acids:

[0235] Acetone dicarboxylic acid (melting point: 138℃, boiling point: 408.4℃)

[0236] Other organic acids:

[0237] glutaric acid, p-toluenesulfonic acid

[0238] Amine:

[0239] 2-ethylimidazole, triethylenetetramine

[0240] N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine

[0241] Terminal diamine polyethylene glycol-polypropylene glycol copolymer (weight average molecular weight 600)

[0242] Specific solvent:

[0243] α-terpineol (boiling point: 217°C), ethylene glycol monophenyl ether (boiling point: 237°C), hexylene glycol (boiling point: 197°C)

[0244] Other solvents:

[0245] Diethylene glycol monohexyl ether (boiling point: 258°C), diethylene glycol mono-2-ethylhexyl ether (boiling point: 272°C)

[0246] Surfactant:

[0247] Polyoxyethylene-resorcinol (weight average molecular weight 1136)

[0248] Polyoxyethylene behenyl ether (average added moles of ethylene oxide: 30 mol)

[0249] Preparation of Solder Paste

[0250] Solder pastes were prepared by mixing the flux of each example with the solder alloy powder below. All prepared solder pastes contained 11 mass% flux and 89 mass% solder alloy powder.

[0251] The solder alloy powder in the solder paste is a powder composed of a solder alloy in which Ag is 3 mass%, Cu is 0.5 mass%, and the remainder is Sn.

[0252] The solidus temperature of this solder alloy is 217°C, and the liquidus temperature is 219°C.

[0253] The solder alloy powder is a size (particle size distribution) that satisfies symbol 4 in the classification of powder sizes in JIS Z 3284-1: 2014 (Table 2).

[0254] <Evaluation of Void Area Ratio>

[0255] Verification method:

[0256] A metal mask (the size of the opening is the same as the size of the electrode, mask thickness 80 μm) was used, and solder paste was printed on the Ni / Au-plated electrode. Then, a QFN (one side length 4 mm, one side length of the bottom electrode 1.7 mm) was mounted on the electrode on which the solder paste was printed. Then, reflow was performed and soldered.

[0257] Figure 1 is a diagram showing a reflow profile. The reflow profile was preheated by holding at 180°C from 150°C for 70 seconds, held at 220°C or higher for 60 seconds, and the peak was at 245°C.

[0258] For the soldered joint, the void area was measured by irradiating X-rays from the vertical direction of the substrate and analyzing the transmitted X-rays. For the measurement, the XD 7600NT Diamond X-ray inspection system (manufactured by Nordson DAGE) was used. In measuring the void area, if the X-rays passed through at least one void, the void was considered to be present and measured. Voids with a diameter of 0.1 μm or larger were detected. Then, the ratio of the total void area to the total area of ​​the bottom electrode was calculated and expressed as the void area percentage (%).

[0259]

[0260]

[0261] When the flux of Comparative Examples 1 and 2, which does not contain a specific solvent, was used, the occurrence of voids could not be sufficiently suppressed.

[0262] In addition, the fluxes of Comparative Examples 3 and 4, which do not contain specific keto acids, could not sufficiently suppress the occurrence of voids.

[0263] When using the flux of Examples 1 to 9 containing specific keto acids and specific solvents, the occurrence of voids could be suppressed more effectively compared to when using the flux of the Comparative Example.

[0264] The flux of Example 1 containing levulinic acid (boiling point 245°C) and α-terpineol (boiling point 217°C) was able to further suppress the occurrence of voids in the flux of Example 4 containing pyruvate (boiling point 165°C) and α-terpineol (boiling point 217°C).

[0265] In Example 1, when the reflow temperature reaches the solder melting temperature, levulinic acid (a specific keto acid) volatilizes along with α-terpineol, which has already begun to volatilize. On the other hand, in Example 4, volatilization of pyruvate (a specific keto acid) proceeds before the reflow temperature reaches the solder melting temperature, and then α-terpineol volatilizes. Due to this difference, it can be assumed that the flux of Example 1 makes it easier to discharge voids from the solder paste than the flux of Example 4. Industrial applicability

[0266] According to the present invention, a flux and a solder paste capable of further suppressing the occurrence of voids can be provided. This flux and solder paste are suitable for soldering QFNs, etc., which do not have leads around the package.

Claims

Claim 1 A water-soluble flux comprising a keto acid having a melting point of 40°C or lower, a solvent having a boiling point of 240°C or lower, a nonionic surfactant, and an amine, wherein the content of the keto acid is 10% or more and 25% or less with respect to 100% by weight of the total amount of the water-soluble flux, the content of the solvent having a boiling point of 240°C or lower is 10% or more and 70% or less with respect to 100% by weight of the total amount of the water-soluble flux, the ratio of the keto acid to the solvent having a boiling point of 240°C or lower is 0.60 to 4.0 as a mass ratio of the solvent having a boiling point of 240°C or lower to the keto acid, the solvent having a boiling point of 240°C or lower comprises one or more selected from the group consisting of phenyl glycol, hexylene glycol, and α-terpineol, and the amine is an azole, A water-soluble flux comprising one or more selected from the group consisting of triethylenetetramine, terminal diamine polyalkylene glycol, and aliphatic amine polyoxyalkylene adduct, wherein the content of the aliphatic amine polyoxyalkylene adduct is 10 mass% or more and 40 mass% or less with respect to the total mass of the flux. Claim 2 In claim 1, the keto acid is additionally a water-soluble flux having a boiling point of 250°C or lower. Claim 3 A water-soluble flux according to claim 1, wherein the keto acid comprises an organic acid having one carboxyl group in its molecule. Claim 4 In claim 3, the keto acid is a water-soluble flux comprising levulinic acid. Claim 5 A water-soluble flux according to claim 1, wherein the content of the nonionic surfactant is 5 mass% or more and 75 mass% or less with respect to the total amount of the water-soluble flux, 100 mass%. Claim 6 A water-soluble flux according to claim 1, wherein the total content of the azoles and the triethylenetetramine is 0.5 mass% or more and 6 mass% or less with respect to the total mass of the flux. Claim 7 A water-soluble flux according to claim 1, further comprising one or more organic acids selected from the group consisting of carboxylic acids and organic sulfonic acids, wherein the content of said organic acid is 1 mass% or more and 10 mass% or less with respect to the total mass of the flux. Claim 8 A water-soluble flux according to claim 1, which does not contain one or more resin components selected from the group consisting of rosin and thermosetting resins. Claim 9 A solder paste comprising solder alloy powder and a water-soluble flux according to any one of claims 1 to 8. Claim 10 delete Claim 11 delete Claim 12 delete

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