Flux, solder paste, and method for producing bonded body

Abstract

A flux according to the present invention is characterized by containing: a compound having an oxyalkylene group and an epoxy group; at least one acid anhydride selected from the group consisting of succinic anhydride and derivatives thereof; a rosin; a solvent; a thixotropic agent; and an activator. A method for producing a bonded body according to the present invention is characterized by including a step for obtaining a bonded body by soldering a component and a substrate, wherein when soldering, reflow is carried out in an atmospheric environment using a solder paste that contains a solder alloy powder and the flux according to the present invention. The adoption of such a flux and a solder paste containing the flux can suppress the occurrence of flux residue cracking due to temperature changes, even in the case of atmospheric reflow soldering.

Description

Flux, solder paste, and method for manufacturing joint body

[0001] This application claims priority to Japanese Patent Application No. 2024-15212, filed February 2, 2024, the contents of which are incorporated herein by reference.

[0002] When manufacturing electronic components, soldering is used to secure components to a substrate and electrically connect the components to the substrate. Soldering uses flux, solder powder, and a solder paste made by mixing flux and solder powder. Flux chemically removes metal oxides present on the metal surfaces of the objects to be soldered and in the solder, allowing the migration of metal elements at the interface between the two. Therefore, soldering using flux forms an intermetallic compound 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 mounted components is heated in a heating furnace called a reflow furnace. This melts the solder powder contained in the solder paste, bonding the components to the board and resulting in a bonded assembly. To prevent oxidation of components and other parts due to oxygen in the furnace, reflow soldering is sometimes performed in an atmosphere with a reduced oxygen concentration using nitrogen.

[0004] The flux used in this reflow soldering generally contains resin components, solvents, thixotropic agents, activators, etc. The resin components contained in the flux applied to the substrate may remain as flux residue on the bonded body after reflow. The flux residue may crack due to temperature increases caused by operation of a device equipped with the bonded body, or increases or decreases in 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 using the same. The solder paste described in Patent Document 1 is said to suppress cracking in the flux residue even when the temperature of the external environment changes, and also to reduce stickiness of the flux residue.

[0005] JP 2013-94781 A

[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 efforts, there is a demand for reducing the amount of nitrogen used. However, when attempting air reflow soldering using only air in a heating furnace, it is difficult to prevent 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.

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

[0009] [1] Component (P): A flux containing a compound having an oxyalkylene group and an epoxy 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 component (P) is 120 g / eq or more. [4] The flux according to any one of [1] to [3], wherein the component (P) 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] [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-octenylsuccinic anhydride.

[0014] [8] The flux according to any one of [1] to [7], wherein the rosin contains 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, as a mass ratio expressed as rosin / acid anhydride, more than 5 and less than 25.

[0016]

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

[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 component (P): a compound having an oxyalkylene group and an epoxy 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 comprising rosin.

[0019]

[14] A flux containing a reaction product of at least one selected from the group consisting of succinic anhydride, a succinic anhydride derivative, and rosin with component (P): a compound having an oxyalkylene group and an epoxy group, a solvent, a thixotropic agent, an activator, rosin, and at least one acid selected from the group consisting of succinic acid and its derivatives, or an acid anhydride thereof.

[0020]

[15] The flux according to any one of

[11] to

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

[0021]

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

[15] .

[0022]

[17] A method for producing a bonded body, comprising 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

[16] .

[0023] 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.

[0024] FIG. 10 is a diagram showing a reflow profile in the evaluation of the examples.

[0025] In this specification, the terms "comprise" and "contain" are concepts that encompass all of "comprise," "consist essentially of," and "consist of," respectively.

[0026] (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. This flux is suitable for use in reflow soldering, and is particularly effective in suppressing flux residue cracking due to temperature changes in solder joints reflowed in the air. This flux 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.

[0027] <Epoxy Resin Having 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.

[0028] 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.

[0029] The epoxy equivalent of component (P) is preferably 120 g / eq or more, more preferably 150 g / eq to 600 g / eq, and even more preferably 200 g / eq to 450 g / eq. 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.

[0030] The epoxy equivalent of the epoxy resin can be measured by potentiometric titration standardized in JIS K 7236:2001.

[0031] Examples of the component (P) include polyalkylene glycol-type epoxy resins, alkylene oxide-modified bisphenol-type epoxy resins, etc. Preferred examples of the component (P) include polyalkylene glycol-type epoxy resins represented by the following general formula (P1) (hereinafter also referred to as "component (P1)") and alkylene oxide-modified bisphenol-type epoxy resins represented by the following general formula (P2) (hereinafter also referred to as "component (P2)").

[0032] [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 parentheses.

[0033] [In the formula, R ２０ is an epoxy group-containing group. ２０ 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 from each other. n21 and n22 each independently represent the number of repetitions of the structure in parentheses.]

[0034] <Component (P1)> 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 or different. １０Examples of the epoxy group-containing group in (R) include a group consisting of only epoxy groups; a group consisting of only alicyclic epoxy groups; and a group having an epoxy group or an 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 a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group. Examples of polycyclic alicyclic groups include a norbornyl group, an isobornyl group, a tricyclononyl group, a tricyclodecyl group, and a tetracyclododecyl group. The hydrogen atoms of these alicyclic groups may be substituted with an alkyl group, an alkoxy group, a hydroxyl group, or the like. 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 a 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.

[0035] 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 is an ethylene group (—CH ２ CH ２ -), propylene group (-CH(CH ３ )-CH ２ In the formula (P1), n1 represents the number of repetitions of the structure in the parentheses, and is preferably 2 to 25.

[0036] 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.

[0037] <Component (P2)> The component (P2) is an alkylene oxide-modified bisphenol-type epoxy resin represented by the general formula (P2). In the formula (P2), R ２０ is an epoxy group-containing group. ２０may be the same or different. 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.

[0038] 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. ２１ and R ２２ The hydrocarbon groups in R may be chain hydrocarbon groups, alicyclic groups, or aromatic hydrocarbon groups. ２１ and R ２２ are 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 Each of R is preferably a linear alkyl group or a hydrogen atom, and particularly preferably a methyl group or a hydrogen atom. 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.

[0039] 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 is preferably a propylene group (—CH ２ -CH(CH ３ ) -, -CH(CH ３ )-CH ２ -) is more preferred. ２３ may be the same or different. In formula (P2), n21 represents the number of repetitions of the structure in parentheses and is preferably 1 to 12. n22 represents the number of repetitions of the structure in parentheses and is preferably 1 to 12.

[0040] 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.

[0041] In the flux of this embodiment, the component (P) may be used alone or in combination of two or more. 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 components (P1) and (P2), even more preferably containing at least component (P2), and particularly preferably containing a propylene oxide-modified bisphenol-type epoxy resin. Examples of propylene oxide-modified bisphenol-type epoxy resins include propylene oxide-modified bisphenol A-type epoxy resins and propylene oxide-modified bisphenol F-type epoxy resins. Of these, it is most preferable that the component (P) contains a propylene oxide-modified bisphenol A-type epoxy resin. The aforementioned products manufactured by ADEKA Corporation under the trade name "EP-4000S" and manufactured by Asahi Kasei Corporation under the trade name "AER9000" are examples of propylene oxide-modified bisphenol A-type epoxy resins.

[0042] The content of the (P) component in the flux of this embodiment is preferably 3% by mass or more and 17% by mass or less, and more preferably 8% by mass or more and 12% by mass or less, relative to the total mass (100% by mass) of the flux. When the content of the (P) component is equal to or more than the lower limit of the above-mentioned preferred range, the occurrence of flux residue cracking due to temperature changes in the case of air reflow soldering is easily suppressed, and when the content is equal to or less than the upper limit of the above-mentioned preferred range, the stickiness of the flux residue is easily reduced.

[0043] <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 acid anhydride as long as it acts as a curing agent for component (P).

[0044] The succinic anhydride derivatives referred to here are those derived from succinic anhydride by removing the two methylene groups (-CH ２ -) or both hydrogen atoms are replaced.

[0045] Preferred examples of the component (AA) include compounds represented by the following general formula (AA-1).

[0046] [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.

[0047] In the formula (AA-1), R ０１ and R ０２ R are each independently a hydrocarbon group which may have a substituent, or a hydrogen atom. ０１ and R ０２ The number of carbon atoms in each hydrocarbon group in R is preferably 1 to 20. ０１ and R ０２ The hydrocarbon groups in may be chain hydrocarbon groups, alicyclic groups, or aromatic hydrocarbon groups.

[0048] 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.

[0049] 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 R are preferably chain hydrocarbon groups, and among these, chain unsaturated aliphatic hydrocarbon groups are more preferred. ０１ and R ０２ The 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.

[0050] 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 When the bond is a double bond, the bond between the carbon atom constituting the five-membered ring and R ０１ In the case of a double bond, the carbon atom constituting the five-membered ring and R ０２ is, for example, a vinylidene group.

[0051] Specific examples of the component (AA) are shown below.

[0052]

[0053]

[0054]

[0055] In the flux of this embodiment, the (AA) component may be used alone or in combination of two or more. The (AA) component preferably contains at least one selected from the group consisting of compounds represented by the above 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 selected from the group consisting of compounds represented by the above chemical formulas (AA-1-1) to (AA-1-9), and even more preferably at least one selected from the group consisting of compounds represented by the above chemical formulas (AA-1-1) to (AA-1-7), and particularly preferably contains the compound represented by the above chemical formula (AA-1-5), i.e., 2-octenylsuccinic anhydride.

[0056] The content of component (AA) in the flux of this embodiment is preferably 0.5% by mass to 5% by mass, and more preferably 1% by mass to 3% by mass, relative to the total mass (100% by mass) of the flux. When the content of component (AA) is equal to or greater than the lower limit of the preferred range, the occurrence of flux residue cracking due to temperature changes in air reflow soldering is easily suppressed, and when the content is equal to or less than the upper limit of the preferred range, the stickiness of the flux residue is easily reduced.

[0057] <Rosin> The flux of the present embodiment contains rosin. In the present invention, the term "rosin" encompasses natural resins containing abietic acid as a main component, including a mixture of abietic acid and its isomers, and chemically modified natural resins (sometimes referred to as rosin derivatives).

[0058] 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, among components constituting a compound, is contained in the compound at a content of 40% by mass or more.

[0059] Representative isomers of abietic acid include neoabietic acid, palustric acid, levopimaric acid, etc. Examples of the "natural resins" include gum rosin, wood rosin, tall oil rosin, etc.

[0060] 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.

[0061] Examples of rosin derivatives include purified rosin, modified rosin, etc. 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 rosin, 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.

[0062] Examples of rosin amines include dehydroabietylamine, dihydroabietylamine, etc. The rosin amine refers to a so-called disproportionated rosin amine.

[0063] 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 at least one selected from the group consisting of acid-modified rosin, hydrogenated rosin, polymerized rosin, and acid-modified hydrogenated rosin, even more preferably at least one selected from the group consisting of acid-modified hydrogenated rosin, hydrogenated rosin, and polymerized rosin, particularly preferably at least one selected from the group consisting of acid-modified hydrogenated rosin and polymerized rosin, and most preferably at least acid-modified hydrogenated rosin. From the viewpoint of solderability, acrylic acid-modified hydrogenated rosin is preferred as the 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.

[0064] The rosin content in the flux of this embodiment is preferably 10% by mass or more, more preferably 10% by mass or more and 32.5% by mass or less, and even more preferably 15% by mass or more and 25% by mass or less, relative to the total mass (100% by 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 is more easily melted, and solderability is more easily improved. When the rosin content is equal to or less than the upper limit of the preferred range, flux residue is more easily reduced.

[0065] 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 to 20, even more preferably 6.5 to 17.5, and particularly preferably 12.5 to 15. If the mass ratio expressed as rosin / 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.

[0066] 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 expressed as 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 the case of air reflow soldering is easily suppressed, and when it is equal to or greater than the lower limit of the above-mentioned preferred range, the stickiness of the flux residue is easily reduced.

[0067] <Solvent> The flux of this embodiment contains a solvent, such as water, alcohol-based solvents, glycol ether-based solvents, and terpineols.

[0068] 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-ethylhexylmethylpropane, 2,4 ...ethylhexylmethylpropane, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyne-2,5-diol, 2,3-dimethyl-2,3-butanediol, 2-ethylhexylmethylpropane, 2,4-ethylhexylmethylpropane, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyne-2,5-diol, 2,3-dimethyl-2,3-butanediol, 2-ethylhexylmethylpropane, 2,4-ethylhexylmethylpropane, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyne-2,5-diol, 2,3-dimethyl-2,3-butanediol, 2-ethylhexylmethylpropane, 2,4-ethylhexylmethylpropane, 2,5-dimethyl- 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.

[0069] 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.

[0070] Examples of terpineols include α-terpineol, β-terpineol, γ-terpineol, terpineol mixtures (i.e., mixtures whose main component is α-terpineol and contain β-terpineol or γ-terpineol), etc. Other examples of solvents include dioctyl sebacate, liquid paraffin, etc.

[0071] In the flux of this embodiment, the solvent may be used alone or in combination of two or more. Among the above, glycol ether solvents are preferred, and in particular, from the viewpoints of viscosity stability when made into a solder paste and the melting property of the solder alloy powder, it is more preferred to use diethylene glycol monohexyl ether and triethylene glycol monomethyl ether in combination.

[0072] The content of the solvent in the flux of this embodiment is the remainder of the flux and is determined depending on the contents of the other components. For example, the content of the solvent in the flux of this 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.

[0073] <Thixotropic Agent> The flux of this embodiment contains a thixotropic agent. Examples of the thixotropic agent include an amide-based thixotropic agent, an ester-based thixotropic agent, and a sorbitol-based thixotropic agent.

[0074] Examples of amide-based thixotropic agents 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 amides, hexamethylene hydroxystearic acid amide, substituted amides, methylol stearic acid amide, methylol amide, and fatty acid ester amide. Examples of bisamides include ethylene bisfatty acid (fatty acid having 6 to 24 carbon atoms) amide, ethylene bishydroxyfatty acid (fatty acid having 6 to 24 carbon atoms) amide, hexamethylene bisfatty acid (fatty acid having 6 to 24 carbon atoms) amide, hexamethylene bishydroxyfatty acid (fatty acid having 6 to 24 carbon atoms) amide, and aromatic bisamides. Examples of fatty acids that are raw materials for the bisamides include stearic acid (number of carbon atoms: C18), oleic acid (number of carbon atoms: C18), lauric acid (number of carbon atoms: C12), etc. 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 acyclic amide oligomers.

[0075] 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.

[0076] 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 a terminal molecule, 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.

[0077] Examples of the ester-based thixotropic agent include ester compounds, and specific examples thereof include hydrogenated castor oil and ethyl myristate.

[0078] 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.

[0079] In the flux of this embodiment, the thixotropic agent may be used alone or in combination of two or more. 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 more preferably, an amide-based thixotropic agent and an ester-based thixotropic agent are used in combination, for example, a combination of polyamide and hydrogenated castor oil.

[0080] The content of the thixotropic agent in the flux of this embodiment is preferably 2% by mass or more and 15% by mass or less, more preferably 4% by mass or more and 12% by mass or less, and even more preferably 5% by mass or more and 9% by mass or less, relative to the total mass (100% by mass) of the flux. When the content of the thixotropic agent is equal to or more than the lower limit of the above-mentioned preferred range, the stability over time (suppression of flux separation over time) is easily 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 easily prevented from becoming too high.

[0081] <Activator> The flux of this embodiment contains an activator. Examples of the activator include organic acids, halogen compounds, and amines. The total content of the activator in the flux of this embodiment is preferably 25% by mass or less, more preferably 2.5% by mass or more and 20% by mass or less, and even more preferably 6% by mass or more and 15% by mass or less, relative to the total mass (100% by mass) of the flux.

[0082] Organic Acids Examples of organic acids include carboxylic acids and organic sulfonic acids. Examples of the carboxylic acids include aliphatic carboxylic acids and aromatic carboxylic acids.

[0083] 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, 3-hydroxypicolinic acid, etc. 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), p-phthalic acid (terephthalic acid), etc.

[0084] Examples of organic sulfonic acids include aliphatic sulfonic acids, aromatic sulfonic acids, etc. Examples of aliphatic sulfonic acids include alkanesulfonic acids, alkanolsulfonic acids, etc.

[0085] Examples of alkane sulfonic acids 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. 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.

[0086] 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, dicarboxylic acids are preferred, aliphatic dicarboxylic acids are more preferred, and at least one selected from the group consisting of oxalic acid, adipic acid, sebacic acid, and eicosanedioic acid is even more preferred. The content of the organic acid in the flux of this embodiment is preferably 15% by mass or less, more preferably 2% by mass or more and 12% by mass or less, and even more preferably 5% by mass or more and 10% by mass or less, relative to the total mass (100% by mass) of the flux.

[0087] <Halogen Compound> Examples of the halogen compound include amine hydrohalides and organic halogen compounds other than amine hydrohalides.

[0088] Amine hydrohalides are compounds obtained by reacting an amine with a hydrogen halide. Examples of the amine include aliphatic amines, azoles, and guanidines. Examples of the hydrogen halide 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.

[0089] Examples of organic halogen compounds other than amine hydrohalides include halogenated aliphatic compounds. Halogenated aliphatic compounds are compounds in which some or all of the hydrogen atoms constituting the aliphatic hydrocarbon group are substituted with halogen atoms. Examples of halogenated aliphatic compounds include halogenated aliphatic alcohols and halogenated heterocyclic compounds.

[0090] 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, halogenated aliphatic compounds may be used, and halogenated aliphatic alcohols are preferred. 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% by mass or less, more preferably 0.5% by mass or more and 4% by mass or less, and even more preferably 1% by mass or more and 2.5% by mass or less, based on the total mass (100% by mass) of the flux.

[0091] <Amine> Examples of the amine include rosin amine, azoles, guanidines, alkylamine compounds, amino alcohol compounds, etc. Examples of the rosin amine include those exemplified in the above <Rosin>.

[0092] 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]- ... 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 triazole compounds such as 2,6-bis[(1H-benzotriazol-1-yl)methyl]-4-methylphenol, 5-methylbenzotriazole, 1-(1',2'-dicarboxyethyl)benzotriazole, 1-(2,3-dicarboxypropyl)benzotriazole, 1-[(2-ethylhexylamino)methyl]benzotriazole, 2,6-bis[(1H-benzotriazol-1-yl)methyl]-4-methylphenol, 5-methylbenzotriazole; triazine compounds such as 2,4-diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyl-s-triazine; and tetrazole compounds such as 5-phenyltetrazole.

[0093] 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.

[0094] Examples of alkylamine compounds include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, and stearylamine.

[0095] Examples of the amino alcohol compound include alkanolamines such as 1-amino-2-propanol and N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine.

[0096] 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 preferable to use an imidazole compound, particularly from the viewpoint of being effective as an accelerator of the curing reaction between the component (P) and at least one of the component (AA) and rosin. It is more preferable to use an alkyl group-substituted imidazole compound 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, or 1-cyanoethyl-2-ethyl-4-methylimidazole, and among these, it is particularly preferable to use 2-ethylimidazole. The content of the amine in the flux of the present 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.

[0097] <Other Components> The flux of the present embodiment may contain other components as needed in addition to the above-described 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.

[0098] <<Resin Components Other Than Component (P) and Rosin>> Examples of resin components other than rosin-based resins include terpene resins, modified terpene resins, terpene phenolic resins, modified terpene phenolic 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.

[0099] <<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 due to contact with certain compounds. A hindered phenol compound refers to a phenol compound having a bulky substituent (e.g., a branched or cyclic alkyl group such as a t-butyl group) on at least one of the ortho positions of the phenol. Examples of nitrogen compounds in metal deactivators include hydrazide nitrogen compounds, amide nitrogen compounds, triazole nitrogen compounds, and melamine nitrogen compounds.

[0100] <<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.

[0101] [Method for Preparing Flux] 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.

[0102] Among these components, component (P), component (AA), and rosin can be heated such that the epoxy groups in component (P) react with at least one of the carboxy groups in component (AA) generated by hydrolysis and the carboxy groups in rosin to produce reaction product (X). This reaction product (X) has a structural unit (P') derived from component (P) and at least one of the structural units (AA') derived from component (AA) and the structural unit (rosin') derived from rosin. That is, another embodiment of the flux according to the first aspect contains reaction product (X) 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.

[0103] The reactant (X) may be produced during the flux preparation process (e.g., when all ingredients are mixed together), or it may be obtained by pre-reacting the (P) component with at least one of the (AA) component and rosin. However, even in the latter case of pre-reacting the reactant (X), unreacted (P), unreacted (AA), or unreacted rosin may remain in the reaction solution, and typically does. For example, another embodiment of the flux includes one 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 its acid anhydride. Alternatively, another embodiment of the flux includes one that further contains rosin in addition to the reactant (X), solvent, thixotropic agent, and activator. Alternatively, the flux of another embodiment includes a flux containing, in addition to the reactant (X), solvent, thixotropic agent, and activator, at least one acid or acid anhydride selected from the group consisting of succinic acid and its derivatives, and rosin.

[0104] 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.

[0105] In the reaction of the (P) component with at least one of the (AA) component and the rosin, the mixing ratio of the (P) component, the (AA) component, and the rosin is preferably 0.25 or more and 0.8 or less in mass relative to the rosin, from the viewpoints of solderability in the air and suppressing polymerization of the (P) component and the (AA) component. Alternatively, the mass ratio of the (AA) component relative to the rosin is preferably more than 0.04 and less than 0.2. In this case, the amount of rosin is, for example, preferably 10% by mass or more, more preferably 10% by mass or more and 32.5% by mass or less, and even more preferably 15% by mass or more and 25% by mass or less, relative to the total mass (100% by mass) of all the components constituting the flux.

[0106] The generation of reactant (X) can be confirmed by the difference between the amount (charge amount) of each component when preparing the flux and the amount of (unreacted) component quantified in the prepared flux. In preparing the flux, for example, the difference between the amount (charge amount) of the (P) component when preparing the flux and its content in the prepared flux is consumed in the generation of reactant (X). As another example, the difference between the amount (charge amount) of the (AA) component when preparing the flux and its content in the prepared flux is consumed in the generation of reactant (X). As another example, the difference between the amount (charge amount) of the rosin when preparing the flux and its content in the prepared flux is consumed in the generation of reactant (X). For example, a flux containing reactant (X) may have a particularly large difference between the amount (charge amount) of the (P) component when preparing the flux and its content in the prepared flux. Also included is a flux in which almost the entire amount of the component (P) blended (charged) is consumed in the production of the reactant (X).

[0107] 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).

[0108] 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%.

[0109] 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, the reactant (X) is not purified, and the resulting reaction solution is mixed with a solvent, a thixotropic agent, an activator, and, if necessary, other components to prepare a flux containing reactant (X). Alternatively, when pre-reacting component (P) with at least one of component (AA) and rosin, an imidazole compound (preferably an alkyl group-substituted imidazole compound, particularly preferably 2-ethylimidazole) as a curing reaction accelerator can also be used in combination to prepare a flux containing reactant (X).

[0110] 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.

[0111] In the flux of this embodiment, by controlling the mixing ratio of the (AA) component and the rosin, or by controlling the mixing ratio of the (P) component and the rosin, it is possible to easily achieve both the suppression of the occurrence of flux residue cracking due to temperature changes and the reduction of the stickiness of the flux residue.

[0112] (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. This solder paste can be prepared by mixing the solder alloy powder and the flux of the above-described embodiment using a known method. The solder alloy constituting the solder alloy powder can be a solder alloy of a known composition. The solder alloy may be a solder containing only Sn, or a solder alloy such as Sn—Ag, Sn—Cu, Sn—Ag—Cu, Sn—Bi, or Sn—In, or an alloy of these to which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, or P has been added. The solder alloy 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. are added. The solder alloy is preferably a solder alloy that does not contain Pb, and more preferably a solder alloy containing Sn, Ag, and Cu.

[0113] 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.

[0114] Flux Content: The flux content in the solder paste of this embodiment is preferably 5 to 30 mass % relative to the total mass of the solder paste, and more preferably 5 to 15 mass %.

[0115] 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.

[0116] (Method for manufacturing a bonded body) One embodiment of the method for manufacturing 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. In the method for manufacturing such a bonded body, reflow is performed in an air atmosphere using the solder paste according to the second aspect described above. One embodiment of the method for manufacturing such a bonded body will be described below. The method for manufacturing a bonded body according to this embodiment is a method including, in this order, a solder paste application step, a component attachment step, and a reflow step.

[0117] [Solder Paste Application Step] In the solder paste application step, the solder paste according to the second aspect is applied to the surface of a substrate. Examples of the substrate include a printed wiring board, a wafer, etc. Methods for applying the solder paste include, for example, a method of printing and applying the solder paste using a mask having an opening, a method of discharging the solder paste using a dispenser, etc., and a method of transferring the solder paste using a probe pin, etc.

[0118] [Component Mounting Step] In the component mounting step, components such as chips, integrated circuits, transistors, diodes, resistors, and capacitors are mounted on the substrate to which the solder paste has been applied.

[0119] [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, approximately 20 vol% oxygen).

[0120] In the reflow process, the interior of a reflow furnace is heated in an atmospheric environment, and the substrate after component mounting 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, 5 to 30°C higher than the melting point of the solder powder. The heating time may be, for example, 30 seconds to 3 minutes.

[0121] The reflow process may include a preheating process before the main heating process. In the preheating process, the board after component mounting 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.

[0122] According to the method for manufacturing a bonded body of this embodiment described above, by using a solder paste containing the flux of this embodiment, the occurrence of flux residue cracking due to temperature changes in the manufactured bonded body is suppressed even in the case of air reflow soldering. In addition, according to the method for manufacturing a bonded body of this embodiment, since reflow can be performed stably in the air, it can contribute to reducing the amount of nitrogen used, etc.

[0123] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0124] <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 to dissolve uniformly. The mixture was then cooled for 24 hours to obtain the flux.

[0125] 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.

[0126] Epoxy resin: polyethylene glycol diglycidyl ether (trade name: "Denacol EX-850" manufactured by Nagase ChemteX Corporation), R in general formula (P1) １０ is a glycidyl group, R １１ is an ethylene group (-CH ２ CH ２ -), n1 is 2; epoxy equivalent is 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 (-CH ２ CH ２ -), 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 (-CH ２ CH ２ -), n1 is 22; epoxy equivalent 551 (g / eq)

[0127] Polypropylene glycol diglycidyl ether: Trade name "Denacol EX-920" manufactured by Nagase ChemteX Corporation; R in general formula (P1) １０ is a glycidyl group, R １１ is a propylene group (-CH(CH ３ )-CH ２ -), n1 is 3; epoxy equivalent is 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(CH ３ )-CH ２ -), n1 is 11; epoxy equivalent 471 (g / eq)

[0128] Propylene oxide-modified bisphenol A epoxy resin: ADEKA Corporation, trade 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 (-CH ２-CH(CH ３ ) -, -CH(CH ３ )-CH ２ -); epoxy equivalent 260 (g / eq) Asahi Kasei Corporation 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 (-CH ２ -CH(CH ３ ) -, -CH(CH ３ )-CH ２ -); epoxy equivalent 380 (g / eq)

[0129] 1,6-Hexanediol diglycidyl ether: trade name "Denacol EX-212" manufactured by Nagase ChemteX Corporation, epoxy equivalent: 151 (g / eq)

[0130] Bisphenol A epoxy resin: trade name "Epiclon 840" manufactured by DIC Corporation, epoxy equivalent weight 180 (g / eq)

[0131] Fatty acid polycarboxylic acid glycidyl ester mixture: trade name "IPU-22G" manufactured by Okamura Oil Mills, Ltd., 8,13-dimethyl-8,12-eicosadienedioic acid bis(2,3-epoxypropyl) (70% or more), CAS number 78352-82-6; epoxy equivalent 240 (g / eq)

[0132] - Polybutadiene Hydroxyl-terminated liquid polybutadiene "Poly bd R-15HT" manufactured by Idemitsu Kosan Co., Ltd.

[0133] Acid anhydride Succinic anhydride or its derivatives Allyl succinic anhydride R in general formula (AA-1) ０１ Ha-CH ２ CH=CH ２ , R ０２ is a hydrogen atom 2-buten-1-yl succinic anhydride R in general formula (AA-1) ０１ Ha-CH ２ CH=CHCH ３ , R ０２ is a hydrogen atom 2-octenylsuccinic anhydride R in general formula (AA-1)０１ Ha-CH ２ CH=CH(CH ２ ) ４ CH ３ , R ０２ is a hydrogen atom Tetrapropenyl succinic 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

[0134] Butylsuccinic anhydride (melting point: 46°C) R in formula (AA-1) ０１ Ha-(CH ２ ) ３ CH ３ , R ０２ is a hydrogen atom n-octylsuccinic anhydride (melting point 65°C) R in formula (AA-1) ０１ Ha-(CH ２ ) ７ CH ３ , 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

[0135] Maleic anhydride (melting point 54°C) Phthalic anhydride (melting point 131°C)

[0136] Aliphatic polycarboxylic acid polyanhydride mixture: Trade name "IPU-22AH" manufactured by Okamura Oil Mills, Ltd., a polyanhydride of aliphatic polycarboxylic acid mixture (70% or more isodocosadienedioic acid), main substance name: 8,12-eicosadienedioic acid, 8,13-dimethyl-, homopolymer; CAS number 86851-05-0

[0137] Rosin: Acrylic acid modified hydrogenated rosin, polymerized rosin, and hydrogenated rosin were used.

[0138] Solvent: Diethylene glycol monohexyl ether (HeDG) and triethylene glycol monomethyl ether (methyl triglycol (MTG)) were used.

[0139] Thixotropic agent Polyamide (saturated fatty acid polyamide, melting point 200°C or less) and hydrogenated castor oil were used.

[0140] ・Activator Organic acid Oxalic acid, adipic acid, sebacic acid, and eicosanedioic acid were used as dicarboxylic acids. Hydrogenated dimer acid was used as dimer acid. Trans-2,3-dibromo-2-butene-1,4-diol was used as halogen compound. 2-Ethylimidazole was used as imidazole compound.

[0141] <Preparation of Solder Paste> Each of the fluxes of the above-described Examples and Comparative Examples was mixed with the solder alloy powder shown below to prepare a solder paste. Each of the prepared solder pastes contained 11 mass % of flux and 89 mass % of solder alloy powder.

[0142] Solder alloy powder: A 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.

[0143] <Evaluation> Evaluation of solderability, resistance to flux residue cracking, and resistance to flux residue stickiness were carried out as follows. The results of these evaluations are shown in Tables 1 to 13.

[0144] [Evaluation of Solderability] After printing solder paste on the Cu lands, reflow (air reflow) was performed in an atmospheric environment. 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. Solderability was then 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.

[0145] Criteria for evaluation: A: The number of Cu lands where unmelted or partially unmelted occurred is 15 or less. B: The number of Cu lands where unmelted or partially unmelted occurred is 16 to 32. C: The number of Cu lands where unmelted or partially unmelted occurred is 33 or more.

[0146] [Evaluation of flux residue crack prevention properties] A printed circuit board (material: FR-4, thickness 1.0 mm, land dimensions 1.5 mm x 0.25 mm, pitch 0.5 mm, land spacing 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, using the printed circuit board after printing, reflow soldering was performed in the air (air reflow) to obtain a test board. The reflow conditions (reflow profile) were the same as those in [Evaluation of solderability] above (FIG. 1).

[0147] Next, each test substrate obtained was placed in a heat cycle tester, and 1000 cycles were performed, with one cycle consisting of leaving the substrate stationary at a low temperature (-40°C) and a high temperature (85°C). In this cycle, the time for leaving the substrate stationary at both the low and high temperatures was 30 minutes, and the total time for one cycle was set to 70 minutes. After 1000 cycles, the flux residue was observed for cracks, and the flux residue crack prevention property was evaluated based on the following criteria.

[0148] Evaluation criteria: A: No cracks even after 1000 cycles. B: No cracks even after 500 cycles. C: Cracks of 0.125 mm or less appear after 500 cycles. D: Cross-sectional cracks appear after 500 cycles.

[0149] [Evaluation of Flux Residue Anti-stickiness] Flux was printed on the Cu lands of the substrate and then reflowed 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%. The flux residue on the stored substrate was touched with a finger to confirm stickiness. The anti-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 for the nitrogen atmosphere (Figure 1). Note that the reflow conditions for evaluating the anti-stickiness of the flux residue were set to a nitrogen atmosphere because the flux residue is more sticky when reflowed in a nitrogen atmosphere than when reflowed in an air atmosphere.

[0150] Judgment criteria A: No sticky flux residue within 1 day after soldering B: No sticky flux residue within 3 days after soldering C: No sticky flux residue within 7 days after soldering D: Sticky flux residue even after 7 days after soldering

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[0152]

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[0162]

[0163] 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.

[0164] [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 evaluated in air (nitrogen approximately 80 vol%, oxygen approximately 20 vol%) and nitrogen (oxygen concentration 3000 ppm). The evaluation results are shown in Table 13.

[0165]

[0166] The results shown in Table 13 confirm that the occurrence of flux residue cracking due to temperature changes cannot be suppressed in air reflow soldering when the fluxes of Comparative Examples 7 to 9 are used. In contrast, the flux of Example 8, to which the present invention is applied, suppresses the occurrence of flux residue cracking due to temperature changes in air reflow soldering, and is therefore particularly suitable for air reflow soldering.

[0167] 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. Component (P): A flux containing a compound having an oxyalkylene group and an epoxy 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.

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. The flux according to claim 1, wherein the epoxy equivalent of component (P) is 120 g / eq or more.

4. The flux according to claim 1, wherein the component (P) 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): [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. The flux of claim 1, wherein the acid anhydride comprises 2-octenyl succinic anhydride.

8. 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 flux according to claim 1, wherein the mixing ratio of said acid anhydride to said rosin is greater than 5 and less than 25 as a mass ratio expressed as rosin / acid anhydride.

10. The flux according to claim 1, wherein the mixing ratio of the (P) component to the rosin is 4.0 or less as a mass ratio expressed as rosin / (P) component.

11. A flux comprising: a reaction product of at least one member selected from the group consisting of succinic anhydride, a succinic anhydride derivative, and rosin with component (P): a compound having an oxyalkylene group and an epoxy group; a solvent; a thixotropic agent; an activator; rosin; and at least one acid selected from the group consisting of succinic acid and its derivatives, or an acid anhydride thereof.

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

13. A solder paste containing a solder alloy powder and the flux according to any one of claims 1 to 12.

14. 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 claim 13.

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