Method for manufacturing flux, solder paste, and conjugate

Abstract

To provide a method for manufacturing flux, solder paste, and a conjugate which can suppress the generation of flux residue cracks due to temperature changes even in the case of ambient air reflow soldering.SOLUTION: A flux related to the present invention is characterized by containing an epoxy resin having an oxyalkylene group, at least one kind of acid anhydride selected from the group consisting of a succinic anhydride and its derivative, rosin, a solvent, a thixotropic agent, and an activator. A method for manufacturing a conjugate related to the present invention includes a process of obtaining a conjugate by soldering components with a circuit board, and is characterized by reflowing under an ambient air atmosphere with a solder paste containing a solder alloy powder and the flux related to the present invention.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a flux, a solder paste, and a method for manufacturing a joint. [Background technology]

[0002] When manufacturing electronic components, soldering is used to fix components to a substrate and electrically connect the components to the substrate, using flux, solder powder, and a solder paste made by mixing the flux and solder powder. Flux chemically removes metal oxides present in the solder and the metal surfaces of the objects being soldered, allowing the movement of metal elements at the interface between the two. Therefore, when soldering is performed using flux, an intermetallic compound is formed between the two, resulting in a strong bond.

[0003] In soldering using solder paste, the solder paste is first printed on a board, components are then mounted, and the board with the components mounted is heated in a heating furnace called a reflow furnace, which melts the solder powder contained in the solder paste and bonds the components to the board, resulting in a bonded assembly. During soldering, reflow soldering is sometimes performed in an atmosphere in which the oxygen concentration in the furnace is reduced by using nitrogen to prevent oxidation of parts, etc. due to oxygen in the furnace.

[0004] The flux used in this reflow soldering generally contains a resin component, a solvent, a thixotropic agent, an activator, and the like. Resin components contained in the flux applied to the board may remain as flux residue on the bonded body after reflow. The flux residue may cause cracks due to temperature rise caused by operation of the device equipped with the bonded body, or due to an increase or decrease in the ambient temperature. In response to this, for example, Patent Document 1 proposes a flux that combines rosin and polybutadiene with a high iodine value, and a solder paste that uses this flux. The solder paste described in Patent Document 1 is said to prevent cracks from occurring in the flux residue even when the temperature of the external environment changes, and also makes the flux residue less likely to become sticky. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-94781 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, the solder industry has also been developing flow soldering manufacturing methods and related products to contribute to achieving carbon neutrality. Among these, there is a demand for reducing the amount of nitrogen used. However, when atmospheric reflow soldering using only air in a heating furnace is attempted, it is difficult to prevent the occurrence of flux residue cracking due to temperature changes with conventional solder paste.

[0007] The present invention has been made in view of the above circumstances, and provides a flux and solder paste that can suppress the occurrence of flux residue cracking due to temperature changes even in the case of air reflow soldering, and a method for manufacturing a bonded body using the flux and solder paste. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention employs the following configuration.

[0009] [1] A flux comprising an epoxy resin having an oxyalkylene group, at least one acid anhydride selected from the group consisting of succinic anhydride and its derivatives, rosin, a solvent, a thixotropic agent, and an activator.

[0010] [2] The flux according to [1], wherein the oxyalkylene group is at least one selected from the group consisting of an oxyethylene group and an oxypropylene group. [3] The flux according to [1] or [2], wherein the epoxy equivalent of the epoxy resin is 120 g / eq or more. [4] The flux according to any one of [1] to [3], wherein the epoxy resin contains a propylene oxide-modified bisphenol-type epoxy resin.

[0011] [5] The flux according to any one of [1] to [4], wherein the acid anhydride is a compound represented by the following general formula (AA-1):

[0012] [ka] [In the formula, R 01 and R 02 are each independently a hydrocarbon group which may have a substituent, or a hydrogen atom. 01 The bond between the carbon atoms constituting the five-membered ring and R is a double bond or a single bond. 02 The bond to is a double bond or a single bond.

[0013] [6] R in the formula (AA-1) 01 or R 02 is a chain-like unsaturated aliphatic hydrocarbon group having 3 to 18 carbon atoms. [7] The flux according to any one of [1] to [6], wherein the acid anhydride includes 2-octenyl succinic anhydride.

[0014] [8] The flux according to any one of [1] to [7], wherein the rosin comprises at least one selected from the group consisting of acrylic acid-modified hydrogenated rosin, polymerized rosin, and hydrogenated rosin.

[0015] [9] The flux according to any one of [1] to [8], wherein the mixing ratio of the acid anhydride to the rosin is greater than 5 and less than 25 as a mass ratio expressed as rosin / acid anhydride.

[0016]

[10] The flux according to any one of [1] to [9], wherein a mixing ratio of the epoxy resin to the rosin is 4.0 or less as a mass ratio expressed as rosin / epoxy resin.

[0017]

[11] A flux comprising a reaction product of at least one selected from the group consisting of succinic anhydride, a succinic anhydride derivative, and rosin with an epoxy resin having an oxyalkylene group, as well as a solvent, a thixotropic agent, and an activator.

[0018]

[12] The flux according to

[11] , further comprising at least one acid selected from the group consisting of succinic acid and its derivatives, or an acid anhydride thereof.

[13] The flux according to

[11] or

[12] , further containing rosin.

[14] The flux according to any one of

[11] to

[13] , wherein the activator contains an imidazole compound.

[0019]

[15] A solder paste containing a solder alloy powder and the flux according to any one of [1] to

[14] .

[0020]

[16] A method for producing a bonded body, comprising the step of obtaining a bonded body by soldering a component and a substrate, wherein the soldering is performed by reflow in an atmospheric environment using the solder paste according to

[15] . [Effects of the Invention]

[0021] According to the present invention, it is possible to provide a flux and a solder paste that can suppress the occurrence of flux residue cracking due to temperature changes even in the case of air reflow soldering, and a method for manufacturing a bonded body using the flux and the solder paste. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 10 is a diagram showing a reflow profile in the evaluation of the examples. DETAILED DESCRIPTION OF THE INVENTION

[0023] (Flux) One embodiment of the flux according to the first aspect contains an epoxy resin having an oxyalkylene group, at least one acid anhydride selected from the group consisting of succinic anhydride and its derivatives, rosin, a solvent, a thixotropic agent, and an activator. The flux of this embodiment is suitable for use in reflow soldering, and in particular, is capable of suppressing the occurrence of flux residue cracking due to temperature changes at solder joints reflowed in the air. The flux of this embodiment is characterized by the use of a combination of an epoxy resin having an oxyalkylene group and at least one acid anhydride selected from the group consisting of succinic anhydride and its derivatives.

[0024] <Epoxy resin having an oxyalkylene group> The flux of this embodiment contains an epoxy resin having an oxyalkylene group (hereinafter also referred to as "component (P)"). The component (P) is a compound having an oxyalkylene group and an epoxy group, and may be any polymer that hardens by forming a crosslinked structure with the epoxy group.

[0025] Examples of the oxyalkylene group in component (P) include an oxyethylene group, an oxypropylene group, and an oxybutylene group. Of these, at least one selected from the group consisting of an oxyethylene group and an oxypropylene group is preferred from the viewpoint of the balance between hydrophilicity and hydrophobicity.

[0026] The epoxy equivalent of the component (P) is preferably 120 g / eq or more, more preferably 150 g / eq or more and 600 g / eq or less, and even more preferably 200 g / eq or more and 450 g / eq or less. By using component (P) whose epoxy equivalent is within the above-mentioned preferred range, the occurrence of flux residue cracking due to temperature changes can be more easily suppressed in the case of air reflow soldering.

[0027] The epoxy equivalent of the epoxy resin can be measured by potentiometric titration standardized in JIS K 7236:2001.

[0028] Examples of the component (P) include polyalkylene glycol type epoxy resins and alkylene oxide-modified bisphenol type epoxy resins. Preferred examples of the component (P) include a polyalkylene glycol-type epoxy resin represented by the following general formula (P1) (hereinafter also referred to as "component (P1)") and an alkylene oxide-modified bisphenol-type epoxy resin represented by the following general formula (P2) (hereinafter also referred to as "component (P2)"):

[0029] [ka] [In the formula, R 10 is an epoxy group-containing group. 10 may be the same or different. 11 is an alkylene group having 2 to 4 carbon atoms. n1 represents the number of repetitions of the structure in the parentheses.

[0030] [ka] [In the formula, R 20 is an epoxy group-containing group. 20 R may be the same or different. 21 and R 22 are each independently a hydrocarbon group having 1 to 6 carbon atoms or a hydrogen atom. 23 is an alkylene group having 2 to 4 carbon atoms. 23 may be the same or different. n21 and n22 each independently represent the number of repetitions of the structure in parentheses.]

[0031] <(P1) component> The component (P1) is a polyalkylene glycol-type epoxy resin represented by the general formula (P1) above. In the formula (P1), R 10 is an epoxy group-containing group. 10 may be the same as or different from each other. R 10 Examples of the epoxy group-containing group in the formula (I) include a group consisting of only epoxy groups; a group consisting of only alicyclic epoxy groups; and a group having an epoxy group or alicyclic epoxy group and a divalent linking group. The alicyclic group that forms the basic skeleton of the alicyclic epoxy group may be monocyclic or polycyclic. Examples of monocyclic alicyclic groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. Examples of polycyclic alicyclic groups include norbornyl, isobornyl, tricyclononyl, tricyclodecyl, and tetracyclododecyl groups. The hydrogen atoms of these alicyclic groups may be substituted with alkyl, alkoxy, or hydroxyl groups. In the case of a group having an epoxy group or an alicyclic epoxy group and a divalent linking group, it is preferable that the epoxy group or the alicyclic epoxy group is linked via the divalent linking group bonded to an oxygen atom (—O—) in the formula. R 10 The epoxy group-containing group in is preferably a glycidyl group.

[0032] In the formula (P1), R 11 is an alkylene group having 2 to 4 carbon atoms, preferably an alkylene group having 2 or 3 carbon atoms, and more preferably an ethylene group (-CH2CH2-) or a propylene group (-CH(CH3)-CH2-). In the formula (P1), n1 represents the number of repetitions of the structure in the parentheses, and is preferably 2 to 25.

[0033] As the component (P1), commercially available products such as the Denacol series manufactured by Nagase ChemteX Corporation can be used. Specifically, special epoxy compounds in which alcoholic hydroxyl groups are glycidyl etherified (polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether) can be used.

[0034] ≪(P2) component≫ The component (P2) is an alkylene oxide-modified bisphenol-type epoxy resin represented by the general formula (P2) above. In the formula (P2), R 20 is an epoxy group-containing group. 20 may be the same as or different from each other. R 20 The epoxy group-containing group in 10 The epoxy group-containing groups in R 20 The epoxy group-containing group in is preferably a glycidyl group.

[0035] In the formula (P2), R 21 and R 22 are each independently a hydrocarbon group having 1 to 6 carbon atoms or a hydrogen atom. R 21 and R 22 The hydrocarbon groups in R may be chain hydrocarbon groups, alicyclic groups, or aromatic hydrocarbon groups. 21 and R 22are each preferably a chain hydrocarbon group, more preferably an alkyl group having 1 to 5 carbon atoms, and more preferably a methyl group, an ethyl group, a propyl group, or an isopropyl group. 21 and R 22 As each of the groups, a linear alkyl group or a hydrogen atom is preferred, and a methyl group or a hydrogen atom is particularly preferred. In the formula (P2), a plurality of R 21 may be the same or different. 22 may be the same or different. 21 and R 22 are preferably the same as each other.

[0036] In the formula (P2), R 23 is an alkylene group having 2 to 4 carbon atoms, preferably an alkylene group having 2 or 3 carbon atoms, and more preferably a propylene group (-CH2-CH(CH3)-, -CH(CH3)-CH2-). 23 may be the same as or different from each other. In the formula (P2), n21 represents the number of repetitions of the structure in the parentheses, and is preferably 1 to 12. n22 represents the number of repetitions of the structure in the parentheses, and is preferably 1 to 12.

[0037] As the component (P2), commercially available products such as "EP-4000S" manufactured by ADEKA Corporation and "AER9000" manufactured by Asahi Kasei Corporation can be used.

[0038] In the flux of this embodiment, the component (P) may be used alone or in combination of two or more types. The component (P) is preferably at least one selected from the group consisting of polyalkylene glycol-type epoxy resins and alkylene oxide-modified bisphenol-type epoxy resins, more preferably at least one selected from the group consisting of the component (P1) and the component (P2), still more preferably contains at least the component (P2), and particularly preferably contains a propylene oxide-modified bisphenol-type epoxy resin. Examples of propylene oxide-modified bisphenol epoxy resins include propylene oxide-modified bisphenol A epoxy resins, propylene oxide-modified bisphenol F epoxy resins, etc. Among these, it is most preferable that the component (P) contains a propylene oxide-modified bisphenol A epoxy resin. The above-mentioned products manufactured by ADEKA CORPORATION under the trade name "EP-4000S" and manufactured by Asahi Kasei Corporation under the trade name "AER9000" each correspond to propylene oxide-modified bisphenol A-type epoxy resins.

[0039] The content of the (P) component in the flux of this embodiment is preferably 3 mass % or more and 17 mass % or less, and more preferably 8 mass % or more and 12 mass % or less, relative to the total mass (100 mass %) of the flux. When the content of component (P) is at least as large as the lower limit of the above-mentioned preferred range, the occurrence of flux residue cracking due to temperature changes during air reflow soldering is more likely to be suppressed, whereas when the content is at most the upper limit of the above-mentioned preferred range, the stickiness of the flux residue is more likely to be reduced.

[0040] <At least one acid anhydride selected from the group consisting of succinic anhydride and its derivatives> The flux of this embodiment contains at least one acid anhydride selected from the group consisting of succinic anhydride and its derivatives (hereinafter also referred to as "component (AA)"). Component (AA) may be any component as long as it acts as a curing agent for component (P).

[0041] The term "succinic anhydride derivative" as used herein refers to a compound in which the hydrogen atoms in one or both of the two methylene groups (-CH2-) that constitute the five-membered ring of succinic anhydride are substituted.

[0042] A preferred example of the component (AA) is a compound represented by the following general formula (AA-1).

[0043] [ka] [In the formula, R 01 and R 02 are each independently a hydrocarbon group which may have a substituent, or a hydrogen atom. 01 The bond between the carbon atoms constituting the five-membered ring and R is a double bond or a single bond. 02 The bond to is a double bond or a single bond.

[0044] In the formula (AA-1), R 01 and R 02 are each independently a hydrocarbon group which may have a substituent, or a hydrogen atom. R 01 and R 02 The hydrocarbon groups in each of the above preferably have 1 to 20 carbon atoms. R 01 and R 02 The hydrocarbon groups in may be chain hydrocarbon groups, alicyclic groups, or aromatic hydrocarbon groups.

[0045] R 01 and R 02 The chain hydrocarbon group and the alicyclic group in R may each be a saturated hydrocarbon group or an unsaturated hydrocarbon group. 01 and R 02 The chain hydrocarbon group in may be linear or branched.

[0046] Among the above, in the case of air reflow soldering, the occurrence of flux residue cracking due to temperature changes is easily suppressed, so R 01 and R 02 The hydrocarbon groups in each of the above are preferably chain hydrocarbon groups, and among these, chain unsaturated aliphatic hydrocarbon groups are more preferred. Furthermore, R 01 and R 02The hydrocarbon groups in each of the above are preferably chain-like unsaturated aliphatic hydrocarbon groups having 3 to 18 carbon atoms, more preferably chain-like unsaturated aliphatic hydrocarbon groups having 3 to 12 carbon atoms, and particularly preferably chain-like unsaturated aliphatic hydrocarbon groups having 8 carbon atoms.

[0047] In the formula (AA-1), the carbon atoms constituting the five-membered ring and R 01 The bond between the carbon atoms constituting the five-membered ring and R is a double bond or a single bond. 02 The bond between the carbon atom constituting the five-membered ring and R is a double bond or a single bond. 01 For example, a vinylidene group is formed. When the bond is a double bond, the carbon atoms constituting the five-membered ring and R 02 is, for example, a vinylidene group.

[0048] Specific examples of the component (AA) are shown below.

[0049] [ka]

[0050] [ka]

[0051] [ka]

[0052] In the flux of this embodiment, the component (AA) may be used alone or in combination of two or more types. The component (AA) preferably contains at least one compound selected from the group consisting of the compounds represented by the aforementioned chemical formulas (AA-1-1) to (AA-1-9), (AA-1-10), (AA-1-11), and (AA-1-12) to (AA-1-17), more preferably at least one compound selected from the group consisting of the compounds represented by the aforementioned chemical formulas (AA-1-1) to (AA-1-9), even more preferably at least one compound selected from the group consisting of the compounds represented by the aforementioned chemical formulas (AA-1-1) to (AA-1-7), and particularly preferably the compound represented by the aforementioned chemical formula (AA-1-5), i.e., 2-octenylsuccinic anhydride.

[0053] The content of the (AA) component in the flux of this embodiment is preferably 0.5% by mass or more and 5% by mass or less, and more preferably 1% by mass or more and 3% by mass or less, relative to the total mass (100% by mass) of the flux. When the content of component (AA) is at least as large as the lower limit of the aforementioned preferred range, the occurrence of flux residue cracking due to temperature changes during air reflow soldering is more likely to be suppressed, whereas when the content is at most the upper limit of the aforementioned preferred range, the stickiness of the flux residue is more likely to be reduced.

[0054] <Rosin> The flux of the present embodiment contains rosin. In the present invention, "rosin" includes natural resins containing abietic acid as the main component, mixtures of abietic acid and its isomers, and chemically modified natural resins (sometimes referred to as rosin derivatives).

[0055] The content of abietic acid in the natural resin is, for example, 40% by mass or more and 80% by mass or less relative to the natural resin. In this specification, the term "main component" refers to a component that is contained in a compound in an amount of 40 mass % or more.

[0056] Representative isomers of abietic acid include neoabietic acid, parastric acid, and levopimaric acid. Examples of the "natural resin" include gum rosin, wood rosin, tall oil rosin, and the like.

[0057] 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.

[0058] Examples of rosin derivatives include purified rosin and modified rosin. Examples of modified rosins include hydrogenated rosin, polymerized rosin, polymerized hydrogenated rosin, disproportionated rosin, acid-modified rosin, rosin ester, acid-modified hydrogenated rosin, acid anhydride-modified hydrogenated rosin, acid-modified disproportionated rosin, acid anhydride-modified disproportionated rosin, phenol-modified rosin, and α,β-unsaturated carboxylic acid-modified products (acrylated rosin, maleated rosin, fumarated rosin, etc.), as well as purified products, hydrogenated products, and disproportionated products of the polymerized rosins, and purified products, hydrogenated products, and disproportionated products of the α,β-unsaturated carboxylic acid-modified products, rosin alcohol, rosin amine, hydrogenated rosin alcohol, rosin ester, hydrogenated rosin ester, rosin soap, hydrogenated rosin soap, and acid-modified rosin soap.

[0059] Examples of rosin amines include dehydroabietylamine, dihydroabietylamine, etc. The rosin amine refers to a so-called disproportionated rosin amine.

[0060] In the flux of this embodiment, one type of rosin may be used alone, or two or more types may be used in combination. The rosin preferably contains a rosin derivative, more preferably contains at least one selected from the group consisting of acid-modified rosin, hydrogenated rosin, polymerized rosin, and acid-modified hydrogenated rosin, further preferably contains at least one selected from the group consisting of acid-modified hydrogenated rosin, hydrogenated rosin, and polymerized rosin, particularly preferably contains at least one selected from the group consisting of acid-modified hydrogenated rosin and polymerized rosin, and most preferably contains at least acid-modified hydrogenated rosin. From the viewpoint of solderability, the acid-modified hydrogenated rosin is preferably acrylic acid-modified hydrogenated rosin, that is, the rosin preferably contains at least one selected from the group consisting of acrylic acid-modified hydrogenated rosin, polymerized rosin, and hydrogenated rosin. The rosin used in the flux of the present embodiment may be acid-modified hydrogenated rosin alone, a combination of acid-modified hydrogenated rosin and polymerized rosin, a combination of acid-modified hydrogenated rosin and hydrogenated rosin, or polymerized rosin alone.

[0061] The rosin content in the flux of this embodiment is preferably 10 mass% or more, more preferably 10 mass% or more and 32.5 mass% or less, and even more preferably 15 mass% or more and 25 mass% or less, relative to the total mass (100 mass%) of the flux. When the rosin content is equal to or greater than the lower limit of the preferred range, the solder alloy powder melts more easily, and solderability is more likely to be improved. When the rosin content is equal to or less than the upper limit of the preferred range, flux residue is more likely to be reduced.

[0062] In the flux of this embodiment, the mixing ratio of the acid anhydride to the rosin, expressed as a mass ratio of rosin / acid anhydride, is preferably more than 5 and less than 25, more preferably 6 or more and 20 or less, even more preferably 6.5 or more and 17.5 or less, and particularly preferably 12.5 or more and 15 or less. If the mass ratio of rosin to acid anhydride exceeds the lower limit of the above-mentioned preferred range, the stickiness of the flux residue is likely to be reduced, whereas if it is less than the upper limit of the above-mentioned preferred range, the occurrence of flux residue cracking due to temperature changes is likely to be suppressed in the case of air reflow soldering.

[0063] In the flux of this embodiment, the mixing ratio of the epoxy resin to the rosin, expressed as a mass ratio of rosin / epoxy resin, is preferably 4.0 or less, more preferably 1.25 to 3.75, even more preferably 1.33 to 3.33, and particularly preferably 1.5 to 3.0. When the mass ratio of rosin / epoxy resin is equal to or less than the upper limit of the above-mentioned preferred range, the occurrence of flux residue cracking due to temperature changes in air reflow soldering is likely to be suppressed, whereas when the mass ratio is equal to or greater than the lower limit of the above-mentioned preferred range, the stickiness of the flux residue is likely to be reduced.

[0064] <Solvent> The flux of this embodiment contains a solvent. Examples of the solvent include water, alcohol-based solvents, glycol ether-based solvents, and terpineols.

[0065] Examples of alcohol-based solvents include isopropyl alcohol, 1,2-butanediol, 1,3-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, 1,1,1-tris(hydroxymethyl)propane, 2-ethylhexylmethyl ... ethyl-2-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, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 2-hexyl-1-decanol, octanediol, and the like.

[0066] Examples of glycol ether solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, diethylene glycol monohexyl ether (hexyl diglycol: HeDG), diethylene glycol dibutyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, triethylene glycol butyl methyl ether, tetraethylene glycol, tetraethylene glycol dimethyl ether; monoalkyl propylene glycols, and the like.

[0067] Examples of terpineols include α-terpineol, β-terpineol, γ-terpineol, and terpineol mixtures (that is, mixtures whose main component is α-terpineol and contain β-terpineol or γ-terpineol). Other solvents include, for example, dioctyl sebacate and liquid paraffin.

[0068] In the flux of this embodiment, one type of solvent may be used alone, or two or more types may be used in combination. Among the above, glycol ether-based solvents are preferred, and it is particularly preferred to use diethylene glycol monohexyl ether and triethylene glycol monomethyl ether in combination from the viewpoints of viscosity stability when made into a solder paste and the melting property of the solder alloy powder.

[0069] The content of the solvent in the flux of this embodiment is the balance in the flux, and is determined depending on the contents of the other components. For example, the content of the solvent in the flux of the present embodiment may be 20% by mass or more and 70% by mass or less, 25% by mass or more and 60% by mass or less, or 30% by mass or more and 50% by mass or less, relative to the total mass (100% by mass) of the flux.

[0070] <Thixotropic agent> The flux of this embodiment contains a thixotropic agent. Examples of the thixotropic agent include amide-based thixotropic agents, ester-based thixotropic agents, and sorbitol-based thixotropic agents.

[0071] Examples of the amide-based thixotropic agent include monoamides, bisamides, 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), aromatic amide, hexamethylenehydroxystearic acid amide, substituted amides, methylolstearic acid amide, methylolamide, and fatty acid ester amide. Examples of bisamides include ethylene bis fatty acid (fatty acid having from 6 to 24 carbon atoms) amides, ethylene bis hydroxy fatty acid (fatty acid having from 6 to 24 carbon atoms) amides, hexamethylene bis fatty acid (fatty acid having from 6 to 24 carbon atoms) amides, hexamethylene bis hydroxy fatty acid (fatty acid having from 6 to 24 carbon atoms) amides, aromatic bisamides, etc. Examples of fatty acids that are raw materials for the bisamides include stearic acid (having from 18 carbon atoms), oleic acid (having from 18 carbon atoms), and lauric acid (having from 12 carbon atoms). 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.

[0072] Examples of the cyclic amide oligomer include an amide oligomer obtained by cyclic polycondensation of a dicarboxylic acid and a diamine, an amide oligomer obtained by cyclic polycondensation of a tricarboxylic acid and a diamine, an amide oligomer obtained by cyclic polycondensation of a dicarboxylic acid and a triamine, an amide oligomer obtained by cyclic polycondensation of a tricarboxylic acid and a triamine, an amide oligomer obtained by cyclic polycondensation of a dicarboxylic acid, a tricarboxylic acid, and a diamine, an amide oligomer obtained by cyclic polycondensation of a dicarboxylic acid, a tricarboxylic acid, and a triamine, an amide oligomer obtained by cyclic polycondensation of a dicarboxylic acid, a diamine, and a triamine, an amide oligomer obtained by cyclic polycondensation of a tricarboxylic acid, a diamine, and a triamine, and an amide oligomer obtained by cyclic polycondensation of a dicarboxylic acid, a tricarboxylic acid, a diamine, and a triamine.

[0073] 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.

[0074] Examples of the ester-based thixotropic agent include ester compounds, and specific examples thereof include hydrogenated castor oil and ethyl myristate.

[0075] 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.

[0076] In the flux of this embodiment, one type of thixotropic agent may be used alone, or two or more types may be used in combination. Among the above, the thixotropic agent preferably includes at least one selected from the group consisting of amide-based thixotropic agents and ester-based thixotropic agents, and it is more preferable to use an amide-based thixotropic agent and an ester-based thixotropic agent in combination, for example, a combination of polyamide and hydrogenated castor oil.

[0077] The content of the thixotropic agent in the flux of this embodiment is preferably 2 mass% or more and 15 mass% or less, more preferably 4 mass% or more and 12 mass% or less, and even more preferably 5 mass% or more and 9 mass% or less, relative to the total mass (100 mass%) of the flux. When the content of the thixotropic agent is equal to or greater than the lower limit of the above-mentioned preferred range, the stability over time (suppression of flux separation over time) is likely to be improved, while when the content is equal to or less than the upper limit of the above-mentioned preferred range, the initial viscosity of the solder paste is likely to be prevented from becoming too high.

[0078] <Activator> The flux of this embodiment contains an activator, such as an organic acid, a halogen compound, or an amine. The total content of the activator in the flux of this embodiment is preferably 25 mass % or less, more preferably 2.5 mass % or more and 20 mass % or less, and even more preferably 6 mass % or more and 15 mass % or less, relative to the total mass (100 mass %) of the flux.

[0079] ≪Organic acid≫ Examples of the organic acid include carboxylic acids and organic sulfonic acids, including aliphatic carboxylic acids and aromatic carboxylic acids.

[0080] Examples of aliphatic monocarboxylic acids include caproic acid, enanthic acid, caprylic acid, pelargonic acid, isopelargonic acid, capric acid, caproleic acid, lauric acid (dodecanoic acid), undecanoic acid, linderic acid, tridecanoic acid, myristoleic acid, pentadecanoic acid, isopalmitic acid, palmitoleic acid, hiragonic acid, hydnocarpic acid, margaric acid, isostearic acid, elaidic acid, petroselinic acid, moroctic acid, eleostearic acid, talic acid, vaccenic acid, riminoleic acid, vernolic acid, sterculic acid, nonadecanoic acid, eicosanoic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, myristic acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butanoic acid, and the like. Examples of aromatic monocarboxylic acids include salicylic acid, parahydroxyphenylacetic acid, benzoic acid, 2,3-dihydroxybenzoic acid, 2-quinolinecarboxylic acid, 3-hydroxybenzoic acid, p-anisic acid; picolinic acid, and 3-hydroxypicolinic acid. Examples of dicarboxylic acids include oxalic acid, citraconic acid, malonic acid, succinic acid, maleic acid, glutaric acid, diglycolic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, eicosanedioic acid, o-phthalic acid, m-phthalic acid (isophthalic acid), and p-phthalic acid (terephthalic acid).

[0081] Examples of organic sulfonic acids include aliphatic sulfonic acids, aromatic sulfonic acids, etc. Examples of aliphatic sulfonic acids include alkanesulfonic acids, alkanolsulfonic acids, etc.

[0082] Examples of alkanesulfonic acids include methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, 2-propanesulfonic acid, 1-butanesulfonic acid, 2-butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid, decanesulfonic acid, and dodecanesulfonic acid. Examples of alkanol sulfonic acids include 2-hydroxyethane-1-sulfonic acid, 2-hydroxypropane-1-sulfonic acid, 2-hydroxybutane-1-sulfonic acid, 2-hydroxypentane-1-sulfonic acid, 1-hydroxypropane-2-sulfonic acid, 3-hydroxypropane-1-sulfonic acid, 4-hydroxybutane-1-sulfonic acid, 2-hydroxyhexane-1-sulfonic acid, 2-hydroxydecane-1-sulfonic acid, and 2-hydroxydodecane-1-sulfonic acid. Examples of aromatic sulfonic acids include 1-naphthalenesulfonic acid, 2-naphthalenesulfonic acid, p-toluenesulfonic acid, xylenesulfonic acid, p-phenolsulfonic acid, cresolsulfonic acid, sulfosalicylic acid, nitrobenzenesulfonic acid, sulfobenzoic acid, and diphenylamine-4-sulfonic acid.

[0083] When an organic acid is used as an activator, one type may be used alone or two or more types may be used in combination. Among the organic acids, it is preferable to use a dicarboxylic acid, more preferably an aliphatic dicarboxylic acid, and even more preferably at least one selected from the group consisting of oxalic acid, adipic acid, sebacic acid, and eicosanedioic acid. The content of the organic acid in the flux of this embodiment is preferably 15 mass % or less, more preferably 2 mass % or more and 12 mass % or less, and even more preferably 5 mass % or more and 10 mass % or less, relative to the total mass (100 mass %) of the flux.

[0084] <Halogen compounds> Examples of halogen compounds include amine hydrohalides and organic halogen compounds other than amine hydrohalides.

[0085] Amine hydrohalides are compounds obtained by reacting amines with hydrogen halides. Examples of amines include aliphatic amines, azoles, and guanidines. Examples of hydrogen halides include chlorine, bromine, and iodine hydrides. Examples of the aliphatic amine include ethylamine, diethylamine, triethylamine, and ethylenediamine. Examples of the guanidines and azoles include those exemplified in the description of amines below.

[0086] Examples of organic halogen compounds other than amine hydrohalides include halogenated aliphatic compounds, which are compounds 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.

[0087] When a halogen compound is used as an activator, one type may be used alone, or two or more types may be used in combination. Among the halogen compounds, a halogenated aliphatic compound may be used, and a halogenated aliphatic alcohol is preferably used. 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. The content of the halogen compound in the flux of this embodiment is preferably 5 mass % or less, more preferably 0.5 mass % or more and 4 mass % or less, and even more preferably 1 mass % or more and 2.5 mass % or less, relative to the total mass (100 mass %) of the flux.

[0088] Amine Examples of the amine include rosin amine, azoles, guanidines, alkylamine compounds, and aminoalcohol compounds. Examples of rosin amines include those exemplified above in the section on <Rosin>.

[0089] Examples of azoles include 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzophenone ... 1-Benzyl-2-phenylimidazole, 1-Cyanoethyl-2-phenylimidazole, 1-Cyanoethyl-2-undecylimidazolium trimellitate, 1-Cyanoethyl-2-phenylimidazolium trimellitate, 1-Dodecyl-2-methyl-3-benzylimidazolium chloride, 2-Methylimidazoline, 2-Phenylimidazoline, 2,4-Diamino-6-[2'-methylimidazolyl-(1')]-ethoxy]-2,4-di ... 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-dihydroxymethylimidazo imidazole compounds such as 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, epoxy-imidazole adduct, 2-methylbenzimidazole, 2-octylbenzimidazole, 2-pentylbenzimidazole, 2-(1-ethylpentyl)benzimidazole, 2-nonylbenzimidazole, 2-(4-thiazolyl)benzimidazole, and benzimidazole;1,2,4-Triazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol], 6-(2-benzotriazolyl)-4-tert-octyl-6'-tert-butyl-4'-methyl-2,2'-methylenebisphenol, 1,2,3-benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, carboxybenzotriazole, 1-[N Examples of suitable triazole compounds include 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, and 5-methylbenzotriazole; triazine compounds such as 2,4-diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct, and 2,4-diamino-6-methacryloyloxyethyl-s-triazine; and tetrazole compounds such as 5-phenyltetrazole.

[0090] 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.

[0091] Examples of alkylamine compounds include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, and stearylamine.

[0092] Examples of the amino alcohol compound include alkanolamines such as 1-amino-2-propanol and N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine.

[0093] When an amine is used as the activator, one type may be used alone, or two or more types may be used in combination. Among the above, it is preferable to use azoles as the amine. Among azoles, it is particularly preferable to use imidazole compounds from the viewpoint of being effective as accelerators for the curing reaction between the (P) component and at least one of the (AA) component and rosin, and it is more preferable to use alkyl group-substituted imidazole compounds such as 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, and 1-cyanoethyl-2-ethyl-4-methylimidazole, and among these, it is particularly preferable to use 2-ethylimidazole. The content of amine in the flux of this embodiment is preferably 5 mass % or less, more preferably 0.1 mass % or more and 2 mass % or less, and even more preferably 0.2 mass % or more and 1 mass % or less, relative to the total mass (100 mass %) of the flux.

[0094] <Other ingredients> The flux of this embodiment may contain other components as needed in addition to the above-mentioned component (P), component (AA), rosin, solvent, thixotropic agent, and activator. Examples of other components include resin components other than component (P) and rosin, metal deactivators, surfactants, silane coupling agents, antioxidants, and colorants.

[0095] <Resin components other than component (P) and rosin> Examples of resin components other than rosin-based resins 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, and acrylic-polyethylene copolymer 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.

[0096] ≪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. 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. 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.

[0097] <Surfactants> Examples of surfactants include nonionic surfactants and cationic surfactants. Examples of nonionic surfactants include aliphatic alcohol polyoxyethylene adducts, aromatic alcohol polyoxyethylene adducts, polyhydric alcohol polyoxyethylene adducts, aliphatic alcohol polyoxypropylene adducts, aromatic alcohol polyoxypropylene adducts, and polyhydric alcohol polyoxypropylene adducts. Examples of cationic surfactants include diamine-terminated polyethylene glycol, diamine-terminated polyethylene glycol-polypropylene glycol copolymers, aliphatic amine polyoxyethylene adducts, aromatic amine polyoxyethylene adducts, polyvalent amine polyoxyethylene adducts, and polyvalent amine polyoxypropylene adducts.

[0098] [Flux preparation method] The flux of this embodiment can be prepared by mixing an epoxy resin having an oxyalkylene group (component (P)), at least one acid anhydride selected from the group consisting of succinic anhydride and its derivatives (component (AA)), rosin, a solvent, a thixotropic agent, and an activator.

[0099] Among these components, component (P), component (AA), and rosin can be heated to generate reaction product (X) by reacting the epoxy group of component (P) with at least one of the carboxy groups of component (AA) generated by hydrolysis and the carboxy groups of the rosin. This reaction product (X) has a structural unit (P') derived from the component (P) and at least one structural unit selected from the group consisting of a structural unit (AA') derived from the component (AA) and a structural unit (rosin') derived from rosin. That is, another embodiment of the flux according to the first aspect contains a reaction product (X) of at least one selected from the group consisting of succinic anhydride, derivatives of succinic anhydride, and rosin with an epoxy resin having an oxyalkylene group, as well as a solvent, a thixotropic agent, and an activator.

[0100] The reactant (X) may be one produced during the process of preparing the flux (for example, when all of the ingredients are mixed together), or may be one obtained by previously reacting the component (P) with at least one of the component (AA) and rosin. However, even in the latter case where the reactant (X) is prepared by pre-reaction, unreacted component (P), unreacted component (AA), or unreacted rosin may remain in the reaction solution, and usually does remain. For example, another embodiment of the flux includes a flux that further contains, in addition to the reactant (X), solvent, thixotropic agent, and activator, at least one acid selected from the group consisting of succinic acid and its derivatives, or an acid anhydride thereof. Alternatively, another embodiment of the flux includes a flux that further contains, in addition to the reactant (X), solvent, thixotropic agent, and activator, rosin. Alternatively, another embodiment of the flux includes a flux that further contains, in addition to the reactant (X), solvent, thixotropic agent, and activator, at least one acid selected from the group consisting of succinic acid and its derivatives, or an acid anhydride thereof, and rosin.

[0101] There are no particular restrictions on the method for reacting component (P) with at least one of component (AA) and rosin. The reaction temperature is preferably 100 to 250° C., and the reaction time is preferably 5 to 30 minutes.

[0102] In the reaction of component (P) with at least one of component (AA) and rosin, the mixing ratio of component (P), component (AA), and rosin is preferably 0.25 or more and 0.8 or less in mass relative to rosin, from the viewpoints of solderability in the air and suppressing polymerization of component (P) and component (AA). Alternatively, the mass ratio of component (AA) relative to rosin is preferably more than 0.04 and less than 0.2. In this case, the amount of rosin to be blended is, for example, preferably 10 mass% or more, more preferably 10 mass% or more and 32.5 mass% or less, and even more preferably 15 mass% or more and 25 mass% or less, relative to the total mass (100 mass%) of all blended components that make up the flux.

[0103] The generation of the reactant (X) can be confirmed by the difference between the amount of each component mixed (charged amount) when preparing the flux and the amount of (unreacted) component quantified in the prepared flux. In preparing a flux, for example, the difference between the amount of component (P) mixed (charged amount) when preparing the flux and the content in the prepared flux is consumed in the production of reactant (X). As another example, the difference between the amount of component (AA) mixed (charged amount) when preparing the flux and the content in the prepared flux is consumed in the production of reactant (X). As another example, the difference between the amount of rosin mixed (charged amount) when preparing the flux and the content in the prepared flux is consumed in the production of reactant (X). For example, a flux containing reactant (X) may have a particularly large difference between the amount of component (P) added when preparing the flux and the amount of component (P) in the prepared flux, or may have a flux in which almost the entire amount of component (P) added is consumed in the production of reactant (X).

[0104] The content of the (P) component in the prepared flux can be quantified by subjecting a sample extracted from the flux to liquid chromatography / Fourier transform mass spectrometry (LC / FTMS). The contents of the (AA) component and rosin in the prepared flux can be quantified by subjecting a sample extracted from the flux to gas chromatography / mass spectrometry (GC / MS).

[0105] In another embodiment, in a flux containing reactant (X), the content of reactant (X) relative to the total mass (100 mass%) of the flux is, for example, 1 mass% to 20 mass%; the content of component (P) is, for example, 0 mass% to 5 mass%; the total content of at least one acid selected from the group consisting of succinic acid and its derivatives and its acid anhydride is, for example, 0.1 mass% to 4.5 mass%; the content of rosin is, for example, 7 mass% to 30 mass%; the content of solvent is the remainder and is, for example, 20 mass% to 70 mass%; the content of thixotropic agent is, for example, 2 mass% to 15 mass%; and the content of activator is, for example, 2.5 mass% to 25 mass%.

[0106] In the latter case of preparing reactant (X) by pre-reaction, after the reaction of component (P) with at least one of component (AA) and rosin is completed, reactant (X) can be prepared without purification by mixing the reaction solution with a solvent, a thixotropic agent, an activator, and, if necessary, other components, to prepare a flux containing reactant (X). Alternatively, when component (P) is reacted in advance with at least one of component (AA) and rosin, an imidazole compound (preferably an alkyl group-substituted imidazole compound, particularly preferably 2-ethylimidazole) can be used in combination as a curing reaction accelerator to prepare a flux containing reactant (X).

[0107] As explained above, the flux of this embodiment uses, in addition to rosin, solvent, thixotropic agent, and activator, an epoxy resin having an oxyalkylene group (component (P)) and at least one acid anhydride (component (AA)) selected from the group consisting of succinic anhydride and its derivatives. By adopting this combination of component (P) and component (AA), it is possible to provide a flux that can suppress the occurrence of flux residue cracking due to temperature changes, even in the case of air reflow soldering, although the reason is not clear.

[0108] In the flux of this embodiment, by controlling the mixing ratio of the (AA) component to the rosin or by controlling the mixing ratio of the (P) component to the rosin, it is possible to easily suppress the occurrence of flux residue cracking due to temperature changes and reduce the stickiness of the flux residue.

[0109] (solder paste) One embodiment of the solder paste according to the second aspect contains a solder alloy powder and the flux of the above-described embodiment, and can be prepared by mixing the solder alloy powder and the flux of the above-described embodiment using a known method. As the solder alloy constituting the solder alloy powder, a solder alloy having a known composition can be used. The solder alloy may be a solder containing only Sn, or may be a solder alloy such as Sn-Ag, Sn-Cu, Sn-Ag-Cu, Sn-Bi, or Sn-In, or an alloy of these with Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, or P added. The solder alloy may be a Sn-Pb based solder alloy or a Sn-Pb based solder alloy to which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. have been added. The solder alloy is preferably a solder alloy that does not contain Pb, and more preferably a solder alloy that contains Sn, Ag, and Cu.

[0110] The soldering conditions in the soldering step may be appropriately set depending on the melting point of the solder alloy. For example, when a Sn-Ag-Cu solder alloy is used, the molten solder temperature is preferably 230 to 280°C, and more preferably 240 to 260°C. Alternatively, when a Sn-Bi solder alloy (a solder alloy containing Sn and Bi) is used, the molten solder temperature is preferably 170 to 220°C, and more preferably 180 to 200°C.

[0111] Flux Content: The content of the flux in the solder paste of this embodiment is preferably 5 to 30 mass %, and more preferably 5 to 15 mass %, relative to the total mass of the solder paste.

[0112] The solder paste of the present embodiment described above uses the flux of the above-described embodiment, and therefore in the case of air reflow soldering, the occurrence of flux residue cracking due to temperature changes is suppressed, the durability of the solder joint is improved, and the operation of a device equipped with the joint is stabilized.

[0113] (Method of manufacturing a bonded body) One embodiment of the method for producing a bonded body according to the third aspect is a method including a step of obtaining a bonded body by soldering a component and a substrate, wherein the soldering is performed by reflow in an air atmosphere using the solder paste according to the second aspect. An embodiment of a method for producing such a bonded body will be described below. The method for manufacturing a bonded body according to this embodiment includes a solder paste application step, a component attachment step, and a reflow step in this order.

[0114] [Solder paste application process] In the solder paste application step, the solder paste according to the second aspect is applied to the surface of the substrate. Examples of the substrate include a printed wiring board and a wafer. Examples of methods for applying the solder paste include a method of printing and applying the solder paste using a mask with openings, a method of ejecting the solder paste using a dispenser or the like, and a method of transferring the solder paste using a probe pin or the like.

[0115] [Parts installation process] In the component mounting step, components are mounted on the substrate to which the solder paste has been applied. Components include, for example, chips, integrated circuits, transistors, diodes, resistors, and capacitors.

[0116] [Reflow process] The reflow process includes at least an operation of performing reflow in an atmospheric atmosphere (atmospheric reflow). Generally, "atmospheric reflow" refers to soldering in heated air (approximately 80 vol% nitrogen and approximately 20 vol% oxygen).

[0117] In the reflow process, the inside of a reflow furnace is heated in an atmospheric environment, and the board after component attachment is heated to a temperature (i.e., peak temperature) higher than the melting point of the solder powder contained in the solder paste (this is called the main heating process). The heating temperature may be, for example, a temperature higher than the melting point of the solder powder by 5 to 30° C. The heating time may be, for example, 30 seconds to 3 minutes.

[0118] The reflow process may include a preheating step before the main heating step. In the preheating step, the board after mounting the components is heated in a reflow furnace at a temperature lower than the melting point of the solder powder contained in the solder paste. The heating temperature may be, for example, 150 to 180° C. The heating time may be, for example, 1 to 5 minutes.

[0119] According to the manufacturing method of the bonded body of the present embodiment described above, the solder paste containing the flux of the present embodiment is used, and therefore, even in the case of air reflow soldering, the produced bonded body is prevented from generating flux residue cracks due to temperature changes. In addition, according to the method for manufacturing a bonded body according to this embodiment, reflow can be stably performed in the air atmosphere, which can contribute to reducing the amount of nitrogen used. [Example]

[0120] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0121] <Preparation of flux> (Examples 1 to 105, Comparative Examples 1 to 9) The fluxes of the examples and comparative examples were prepared with the compositions shown in Tables 1 to 13. Each flux was prepared as follows: All components were placed in a stainless steel can, heated to approximately 200°C with stirring, and heated for 5 minutes until uniformly dissolved. The mixture was then cooled for 24 hours to obtain the flux.

[0122] In the table, the content of each raw material indicates the ratio (mass %) to the total mass (100 mass %) of the flux. The raw materials used are shown below.

[0123] Epoxy resin Polyethylene glycol diglycidyl ether Nagase ChemteX Corporation's trade name "Denacol EX-850"; R in general formula (P1) 10 is a glycidyl group, R 11 is an ethylene group (-CH2CH2-), n1 is 2; epoxy equivalent 122 (g / eq) Nagase ChemteX Corporation's trade name "Denacol EX-841"; R in general formula (P1) 10 is a glycidyl group, R 11 is an ethylene group (-CH2CH2-), n1 is 13; epoxy equivalent 372 (g / eq) Nagase ChemteX Corporation's trade name "Denacol EX-861"; R in general formula (P1) 10 is a glycidyl group, R 11 is an ethylene group (-CH2CH2-), n1 is 22; epoxy equivalent weight 551 (g / eq)

[0124] Polypropylene glycol diglycidyl ether Nagase ChemteX Corporation's trade name "Denacol EX-920"; R in general formula (P1) 10 is a glycidyl group, R 11 is a propylene group (-CH(CH3)-CH2-), n1 is 3; epoxy equivalent 176 (g / eq) Nagase ChemteX Corporation's trade name "Denacol EX-931"; R in general formula (P1) 10 is a glycidyl group, R 11 is a propylene group (-CH(CH3)-CH2-), n1 is 11; epoxy equivalent weight 471 (g / eq)

[0125] Propylene oxide modified bisphenol A epoxy resin ADEKA Corporation's product name "EP-4000S", R in general formula (P2) 20 is a glycidyl group, R 21 and R 22 are methyl groups, R 23 is a propylene group (-CH2-CH(CH3)-, -CH(CH3)-CH2-); epoxy equivalent 260 (g / eq) Asahi Kasei Corporation's product name "AER9000"; R in general formula (P2) 20 is a glycidyl group, R 21 and R 22 are methyl groups, R 23 is a propylene group (-CH2-CH(CH3)-, -CH(CH3)-CH2-); epoxy equivalent 380 (g / eq)

[0126] 1,6-Hexanediol Diglycidyl Ether Nagase ChemteX Corporation's product name "Denacol EX-212", epoxy equivalent weight 151 (g / eq)

[0127] Bisphenol A epoxy resin DIC Corporation's product name "Epiclon 840", epoxy equivalent weight 180 (g / eq)

[0128] Fatty acid polycarboxylic acid glycidyl ester mixture Okamura Oil Mills' product name "IPU-22G", 8,13-dimethyl-8,12-eicosadienedioic acid bis(2,3-epoxypropyl) (70% or more), CAS number 78352-82-6; epoxy equivalent weight 240 (g / eq)

[0129] Polybutadiene Hydroxyl-terminated liquid polybutadiene Product name: "Poly bd R-15HT" manufactured by Idemitsu Kosan Co., Ltd.

[0130] ·Acid anhydride Succinic anhydride or its derivatives Allyl succinic anhydride R in general formula (AA-1) 01 is -CH2CH=CH2, R 02 is a hydrogen atom 2-Buten-1-yl succinic anhydride R in general formula (AA-1) 01 is -CH2CH=CHCH3, R 02 is a hydrogen atom 2-Octenylsuccinic Anhydride R in general formula (AA-1) 01 is -CH2CH=CH(CH2)4CH3, R 02 is a hydrogen atom Tetrapropenylsuccinic anhydride R in general formula (AA-1) 01 Ha-C 12 H 23 , R 02 is a hydrogen atom Isooctadecenyl succinic anhydride R in general formula (AA-1) 01 Ha-C 18 H 35 , R 02 is a hydrogen atom

[0131] Butylsuccinic anhydride (melting point 46°C) R in general formula (AA-1) 01 is -(CH2)3CH3, R 02 is a hydrogen atom n-Octyl succinic anhydride (melting point 65°C) R in general formula (AA-1) 01 is -(CH2)7CH3, R 02 is a hydrogen atom Succinic anhydride (melting point 120°C) R in general formula (AA-1) 01 is a hydrogen atom, R 02 is a hydrogen atom

[0132] Maleic anhydride (melting point 54°C) Phthalic anhydride (melting point 131°C)

[0133] Aliphatic polycarboxylic acid polyanhydride mixture Okamura Oil Mills, trade name "IPU-22AH", a polyanhydride of aliphatic polycarboxylic acid mixture (70% or more isodocosadienedioic acid), main substance: 8,12-eicosadienedioic acid, 8,13-dimethyl-, homopolymer; CAS number 86851-05-0

[0134] Rosin Acrylic acid modified hydrogenated rosin, polymerized rosin, and hydrogenated rosin were used.

[0135] ·solvent Diethylene glycol monohexyl ether (HeDG) and triethylene glycol monomethyl ether (methyl triglycol (MTG)) were used.

[0136] Thixotropic agents Polyamide (saturated fatty acid polyamide, melting point 200°C or less) and hydrogenated castor oil were used.

[0137] Activators organic acid The dicarboxylic acids used were oxalic acid, adipic acid, sebacic acid, and eicosanedioic acid, and the dimer acid used was hydrogenated dimer acid. Trans-2,3-dibromo-2-butene-1,4-diol was used as the halogen compound. 2-Ethylimidazole was used as the imidazole compound.

[0138] <Preparation of solder paste> Each of the fluxes of the above-described Examples and Comparative Examples was mixed with the following solder alloy powder to prepare a solder paste. Each of the prepared solder pastes contained 11 mass % of flux and 89 mass % of solder alloy powder.

[0139] Solder alloy powder: Powder consisting of a solder alloy containing 0.5 mass% Cu, 3.0 mass% Ag, and the remainder Sn. The solidus temperature of this solder alloy is 217°C and the liquidus temperature is 220°C. The size of the solder alloy powder (particle size distribution) satisfies symbol 4 in the powder size classification (Table 2) of JIS Z 3284-1:2014.

[0140] <Evaluation> The solderability, resistance to flux residue cracking, and resistance to flux residue stickiness were evaluated as follows. The results of these evaluations are shown in Tables 1 to 13.

[0141] [Evaluation of solderability] After printing solder paste on the Cu lands, reflow was performed in the air (air reflow). After reflow, the melted state of the solder on each of the 64 Cu lands was checked, and the number of Cu lands that were unmelted or partially unmelted was counted. Then, the solderability was evaluated based on the following criteria. In this evaluation, the opening diameter was set to 0.30 mm, and the mask thickness was set to 0.15 mm. The reflow conditions (reflow profile) were preheating at 150-180°C for 90 seconds, peak temperature at 240°C, and solder melting time for 40 seconds. This reflow profile is shown in Figure 1.

[0142] Judgment criteria ◎: The number of Cu lands that are unmelted or partially unmelted is 15 or less ○: The number of unmelted or partially unmelted Cu lands is 16 to 32 ×: The number of Cu lands that were unmelted or partially unmelted was 33 or more.

[0143] [Evaluation of flux residue crack prevention] A printed circuit board (material: FR-4, thickness: 1.0 mm, land dimensions: 1.5 mm × 0.25 mm, pitch: 0.5 mm, width between lands: 0.25 mm, number of lands: 64) was prepared. The prepared solder paste was printed on the printed circuit board using a metal mask with a thickness of 150 μm. Next, the printed circuit board was subjected to reflow soldering in an air atmosphere (air reflow) to obtain a test board. The reflow conditions (reflow profile) were the same as those described above in [Evaluation of solderability] (Figure 1).

[0144] Next, each test substrate was placed in a heat cycle tester and subjected to 1000 cycles, with one cycle consisting of exposure to a low temperature (-40°C) and a high temperature (85°C). Each exposure time was 30 minutes, with the total cycle time being 70 minutes. After 1000 cycles, the flux residue was observed for cracks, and the flux residue crack prevention properties were evaluated based on the following criteria:

[0145] Judgment criteria ◎: No cracks even after 1000 cycles 〇: No cracks after 500 cycles △: After 500 cycles, cracks of 0.125 mm or less were observed. ×: Transverse cracks after 500 cycles

[0146] [Evaluation of flux residue stickiness prevention] Flux was printed on the Cu lands of the substrate, and then reflow was performed in a nitrogen atmosphere (oxygen concentration 3000 ppm). After reflow, the substrate was stored at a temperature of 25°C and a relative humidity of 50%. After storage, the flux residue on the board was touched with a finger to check for stickiness, and the ability to prevent stickiness of the flux residue was evaluated based on the following criteria. In this evaluation, the opening diameter was set to 6.5 mm and the mask thickness was set to 0.15 mm. The reflow conditions (reflow profile) were the same as those in the above [Evaluation of solderability], except that the reflow was performed in a nitrogen atmosphere (Figure 1). The reflow conditions for evaluating the ability to prevent flux residue from sticking were set to a nitrogen atmosphere, since the flux residue tends to become more sticky when reflowed in a nitrogen atmosphere compared to when reflowed in the air.

[0147] Judgment criteria ◎: No sticky flux residue within one day after soldering ○: No sticky flux residue within 3 days after soldering △: No sticky flux residue within 7 days after soldering ×: Flux residue remains sticky even after 7 days from soldering

[0148] [Table 1]

[0149] [Table 2]

[0150] [Table 3]

[0151] [Table 4]

[0152] [Table 5]

[0153] [Table 6]

[0154] [Table 7]

[0155] [Table 8]

[0156] [Table 9]

[0157] [Table 10]

[0158] [Table 11]

[0159] [Table 12]

[0160] From the results shown in Tables 1 to 12, it was confirmed that when the fluxes of Examples 1 to 105 to which the present invention is applied are used, the occurrence of flux residue cracking due to temperature changes can be suppressed even in the case of air reflow soldering.

[0161] [Evaluation of differences in reflow conditions (atmosphere)] For the fluxes of Comparative Examples 7 to 9, the reflow conditions for the evaluation of the solderability, the resistance to flux residue cracking, and the resistance to flux residue stickiness were both air atmosphere (nitrogen approximately 80 vol%, oxygen approximately 20 vol%) and nitrogen atmosphere (oxygen concentration 3000 ppm). The evaluation results are shown in Table 13.

[0162] [Table 13]

[0163] From the results shown in Table 13, it was confirmed that when the fluxes of Comparative Examples 7 to 9 were used, the occurrence of flux residue cracking due to temperature changes could not be prevented in the case of air reflow soldering. In contrast, the flux according to Example 8 to which the present invention is applied suppresses the occurrence of flux residue cracking due to temperature changes in the case of air reflow soldering, and is therefore found to be particularly suitable for air reflow soldering.

[0164] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Addition, omission, substitution, and other modifications of the configuration are possible within the scope of the spirit of the present invention. The present invention is not limited by the above description, but is limited only by the scope of the appended claims.

Claims

1. an epoxy resin having an oxyalkylene group; at least one acid anhydride selected from the group consisting of succinic anhydride and derivatives thereof; Rosin and A solvent, Thixotropic agents and an activator; containing, flux.

2. 2. The flux according to claim 1, wherein the oxyalkylene group is at least one selected from the group consisting of an oxyethylene group and an oxypropylene group.

3. 2. The flux according to claim 1, wherein the epoxy resin has an epoxy equivalent of 120 g / eq or more.

4. 2. The flux according to claim 1, wherein the epoxy resin comprises a propylene oxide-modified bisphenol-type epoxy resin.

5. The flux according to claim 1, wherein the acid anhydride is a compound represented by the following general formula (AA-1): 【Chemical 1】 [In the formula, R ０１ and R ０２ are each independently a hydrocarbon group which may have a substituent, or a hydrogen atom. ０１ The bond between the carbon atoms constituting the five-membered ring and R is a double bond or a single bond. ０２ The bond to is a double bond or a single bond.

6. R in the formula (AA-1) ０１ or R ０２ The flux according to claim 5, wherein is a chain unsaturated aliphatic hydrocarbon group having 3 to 18 carbon atoms.

7. 2. The flux of claim 1, wherein the acid anhydride comprises 2-octenyl succinic anhydride.

8. 2. The flux according to claim 1, wherein the rosin comprises at least one selected from the group consisting of acrylic acid-modified hydrogenated rosin, polymerized rosin, and hydrogenated rosin.

9. The mixing ratio of the acid anhydride and the rosin is 2. The flux according to claim 1, wherein the mass ratio of rosin to acid anhydride is greater than 5 and less than 25.

10. The mixing ratio of the epoxy resin and the rosin is 2. The flux according to claim 1, wherein a mass ratio of rosin to epoxy resin is 4.0 or less.

11. a reaction product of at least one selected from the group consisting of succinic anhydride, a derivative of succinic anhydride, and rosin with an epoxy resin having an oxyalkylene group; and A flux containing a solvent, a thixotropic agent and an activator.

12. The flux according to claim 11, further comprising at least one acid selected from the group consisting of succinic acid and its derivatives, or an acid anhydride thereof.

13. The flux of claim 11 further comprising rosin.

14. The flux of claim 11 , wherein the activator comprises an imidazole compound.

15. A solder paste comprising a solder alloy powder and the flux according to any one of claims 1 to 14.

16. The method includes a step of obtaining a bonded assembly by soldering a component and a substrate, A method for producing a bonded body, wherein the soldering is performed by reflow in an air atmosphere using the solder paste according to claim 15.

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