Method for manufacturing flux, solder paste, and bonded structures

Abstract

This invention provides a flux with enhanced heat resistance, a solder paste containing the flux, and a method for manufacturing a bonded body using the flux. [Solution] A flux containing a monocarboxylic acid (B3) represented by general formula (b3) and salicylic acid is used. In the formula, nb31 is an integer between 1 and 4. [C1] TIFF0007866228000017.tif27170

Description

[Technical Field]

[0001] This invention relates to a method for producing flux, solder paste, and bonded products. [Background technology]

[0002] The fixing of components to a circuit board and the electrical connection of components to the circuit board are generally performed by soldering. Soldering involves the use of flux, solder powder, and solder paste, which is a mixture of flux and solder powder. Flux chemically removes metal oxides present on the metal surfaces of the objects to be soldered and the solder itself, allowing for the movement of metal elements at the boundary between them. Therefore, using flux during soldering allows for the formation of intermetallic compounds between the two, resulting in a strong bond.

[0003] In soldering, methods such as reflow soldering and thermal compression bonding (TCB) are employed depending on the size of the objects to be joined and the type of components. Typically, in reflow soldering, the circuit board is preheated (150-190°C, 1-2 minutes), and then the solder paste is melted by reflow (230-250°C, 1-2 minutes). This reflow soldering process is completed in just a few minutes.

[0004] Recently, with the miniaturization of electronic devices and the reduction of circuit board sizes, there has been a demand for space-saving and high-performance components. In this context, the use of surface-mount components, particularly those with array terminal structures such as BGA (Ball Grid Array) and CSP (Chip Size Package), is increasing, mainly for the purpose of high-density mounting.

[0005] In high-density mounting, thin components and circuit boards are used. As a result, reflow soldering makes the components and circuit boards more susceptible to warping. On the other hand, a thermocompression bonding method is adopted for bonding thin components and substrates (for example, Non-Patent Document 1).

[0006] The bonding by thermocompression will be described with reference to FIGS. 1 to 4 as examples. FIG. 1 is a cross-sectional view showing a substrate 10 coated with flux. Lands 11 are arranged on the substrate 10. FIG. 2 is a cross-sectional view showing a component 20 on which solder balls 21 are mounted. FIG. 3 is a cross-sectional view showing the state where the component 20 on which solder balls are mounted and the substrate 10 coated with flux are aligned. FIG. 4 is a cross-sectional view showing the state where the component 20 on which solder balls are mounted and the substrate 10 coated with flux are soldered by thermocompression bonding.

[0007] In the bonding by thermocompression shown in FIG. 4, after applying flux 12 to the substrate 10, the substrate 10 is preheated. Next, the preheated substrate 10 and the component 20 are arranged to face each other, and a bonded body is obtained by thermocompression bonding.

[0008] By the way, a flux containing salicylic acid is used to place the solder balls on the wafer (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Non-Patent Documents

[0010]

Non-Patent Document 1

[0011] In thermocompression bonding as shown in Figure 4, the heating time is limited, making it difficult to sufficiently raise the temperature of large substrates with high heat capacity. Therefore, it is necessary to preheat the flux-coated substrate at a high temperature for an extended period (for example, 220°C for 30 minutes).

[0012] The inventors discovered that when a substrate coated with conventional flux is preheated at high temperatures for an extended period, the accumulation of heat reduces the activity of the flux.

[0013] This invention has been made in view of the above circumstances, and aims to provide a flux with enhanced heat resistance, a solder paste containing the flux, and a method for manufacturing a bonded body using the flux. [Means for solving the problem]

[0014] To solve the above-mentioned problems, the inventors diligently investigated the components of the flux. The inventors discovered that by combining salicylic acid and a specific monocarboxylic acid (monocarboxylic acid (B3) as specified herein) with the flux, the decrease in flux activity can be suppressed even after prolonged preheating at high temperatures (i.e., heat resistance can be increased), and thus completed the present invention.

[0015] The present invention includes the following aspects. [1] A flux containing a monocarboxylic acid (B3) represented by the following general formula (b3) and salicylic acid.

[0016] [Chemical formula] [In the formula, nb31 is an integer of 1 or more and 4 or less.]

[0017] [2] The flux according to [1], wherein in the general formula (b3), nb31 is 1. [3] The flux according to [1] or [2], further containing a compound (SU0) represented by the following general formula (su0).

[0018] [Chemical formula] [In the formula, R a2 ,

[0019] , , , a3 , , , , R a2 and R a3 are each independently an organic group. However, one or more selected from the group consisting of R a1 , R a2 and R a3 has an oxyalkylene group. The total number of repetitions of the oxyalkylene group in R a1 , R a2 and R a3 is 15 to 120.]

[0019] [4] The flux according to any one of [1] to [3], further containing an amine polyoxyalkylene adduct. [5] The flux according to any one of [1] to [4], wherein the total content of the salicylic acid and the monocarboxylic acid (B3) is 10% by mass or more based on the total mass of the flux. [6] The flux according to any one of [1] to [5], wherein the content of rosin is 0 to 1% by mass based on the total mass of the flux. [7] A flux for thermocompression soldering, as described in any one of [1] to [6].

[0020] Solder paste containing the flux described in any one of [8][1] to [7] and solder powder. A method for manufacturing a joint, comprising the step of obtaining a joint by thermally pressing and soldering a soldering surface of a substrate treated with any one of [1] to [7] and a component on which solder balls are placed. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide a flux with enhanced heat resistance, a solder paste containing the flux, and a method for manufacturing a bonded body using the flux. [Brief explanation of the drawing]

[0022] [Figure 1] This is a cross-sectional view showing a substrate with flux applied during soldering by thermocompression bonding. [Figure 2] This is a cross-sectional view showing a component with solder balls attached during soldering by thermocompression bonding. [Figure 3] This is a cross-sectional view showing the alignment of a component with solder balls attached to a substrate coated with flux during thermocompression soldering. [Figure 4] This is a cross-sectional view showing the process of soldering a component with solder balls attached to a substrate coated with flux using thermocompression bonding. [Modes for carrying out the invention]

[0023] In this specification, "include" and "contain" are concepts that encompass all of the following: "include," "consist essentially of," and "consist of." "Include" and "contain" may mean either "consist essentially of" or "consist of."

[0024] In this specification, when the content of a component in a flux is specified as a mass percentage of the total mass of the flux, the total mass of the flux is 100% by mass.

[0025] (Flux) The flux according to this embodiment can be suitably used for both reflow soldering and thermal compression bonding soldering. In particular, this flux is suitable for thermal compression bonding (TCB) soldering. The flux according to this embodiment contains a monocarboxylic acid (B3) represented by the following general formula (b3) and salicylic acid.

[0026] The salicylic acid content is preferably 5 to 20% by mass, and more preferably 7 to 13% by mass, relative to the total mass of the flux. If the salicylic acid content in the flux is within the aforementioned preferred range, the heat resistance of the flux can be easily improved. Furthermore, the decrease in heat resistance due to esterification reactions between monocarboxylic acids (A0) can be more easily suppressed. Additionally, corrosion of substrates and components due to a decrease in the flux pH can be more easily suppressed. If the value is above the lower limit of the aforementioned preferred range, it becomes easier to improve the heat resistance of the flux. If the pH is below the upper limit of the preferred range mentioned above, it becomes easier to suppress the decrease in heat resistance due to the esterification reaction between salicylic acids. In addition, it becomes easier to suppress the corrosion of substrates and components due to the decrease in the pH of the flux.

[0027] <Monocarboxylic acid (B3)> The flux according to this embodiment contains a monocarboxylic acid (B3) represented by the following general formula (b3).

[0028] [ka] [In the formula, nb31 is an integer between 1 and 4 (inclusive).]

[0029] From the viewpoint of further improving the heat resistance of the flux, nb31 is preferably an integer between 1 and 3, more preferably 1 or 2, and even more preferably 1.

[0030] From the viewpoint of further improving the heat resistance of the flux, the monocarboxylic acid (B3) is preferably one or more selected from the group consisting of 2,3-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, and 2,6-dihydroxybenzoic acid, more preferably one or more selected from the group consisting of 2,3-dihydroxybenzoic acid and 2,5-dihydroxybenzoic acid, and even more preferably 2,3-dihydroxybenzoic acid.

[0031] Monocarboxylic acid (B3) may be used alone or in a mixture of two or more types.

[0032] The content of monocarboxylic acid (B3) is preferably 5 to 20% by mass, and more preferably 7 to 13% by mass, relative to the total mass of the flux. If the content of monocarboxylic acid (B3) in the flux is within the aforementioned preferred range, the heat resistance of the flux can be easily improved. In addition, corrosion of the substrate and components due to a decrease in the pH of the flux can be easily suppressed. If the value is above the lower limit of the aforementioned preferred range, it becomes easier to improve the heat resistance of the flux. If the pH is below the upper limit of the aforementioned preferred range, it becomes easier to suppress corrosion of the substrate and components due to a decrease in the flux pH.

[0033] The total content of salicylic acid and monocarboxylic acid (B3) in the flux is preferably 10 to 40% by mass, more preferably 15 to 30% by mass, and even more preferably 15 to 25% by mass, based on the total mass of the flux. If the total content of salicylic acid and monocarboxylic acid (B3) in the flux is within the aforementioned preferred range, the heat resistance of the flux can be easily improved. If the pH is above the lower limit of the aforementioned preferred range, it becomes easier to improve the heat resistance of the flux. In addition, it becomes easier to suppress corrosion of the substrate and components due to a decrease in the pH of the flux. If the pH is below the upper limit of the aforementioned preferred range, it becomes easier to suppress corrosion of the substrate and components due to a decrease in the flux pH.

[0034] The mixing ratio of salicylic acid and monocarboxylic acid (B3) in the flux is preferably 0.25 to 4, more preferably 0.5 to 2, and even more preferably 0.75 to 1.5, expressed as a mass ratio of salicylic acid / monocarboxylic acid (B3). If the mass ratio of salicylic acid / monocarboxylic acid (B3) in the flux is within the preferred range described above, the heat resistance of the flux can be easily improved. In addition, the decrease in heat resistance due to the esterification reaction between monocarboxylic acids (A0) can be easily suppressed. If the mass ratio of salicylic acid / monocarboxylic acid (B3) in the flux is above the aforementioned lower limit, the heat resistance of the flux can be easily improved. If the mass ratio of salicylic acid / monocarboxylic acid (B3) in the flux is below the aforementioned upper limit, it becomes easier to improve the heat resistance of the flux and to suppress the decrease in heat resistance due to the esterification reaction between salicylic acids.

[0035] <Other ingredients> The flux according to this embodiment may contain, or may not contain, other components in addition to salicylic acid and monocarboxylic acid (B3) as needed. Other components include solvents, activators other than salicylic acid and monocarboxylic acid (B3) (other activators), surfactants, thixotropic agents, resin components, metal deactivators, antioxidants, silane coupling agents, colorants, etc.

[0036] The flux according to this embodiment may consist of salicylic acid, monocarboxylic acid (B3), and optionally one or more other surfactants, surfactants, thixotropes, resin components, metal deactivators, antioxidants, silane coupling agents, and colorants. Each component constituting the group of other components can be arbitrarily selected.

[0037] Solvents Examples of solvents include water, alcohol-based solvents, glycol ether-based solvents, and terpineols.

[0038] Examples of alcohol-based solvents include 2-propanol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-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, and 2-ethyl-2-hydroxypropyl alcohol. Examples include roxymethyl-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-decine-4,7-diol, 2-hexyl-1-decanol, 2-methyl-2,4-pentanediol (hexylene glycol), octanediol, and the like.

[0039] Examples of glycol ether solvents include dipropylene glycol monomethyl ether, diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, ethylene glycol monobutyl ether (butyl glycol), ethylene glycol monohexyl ether (hexyl glycol), diethylene glycol monohexyl ether (hexyl diglycol), diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, methyl propylene glycol, triethylene glycol butyl methyl ether, tetraethylene glycol, tetraethylene glycol dimethyl ether, and tripropylene glycol-n-butyl ether.

[0040] Examples of terpineols include α-terpineol, β-terpineol, γ-terpineol, and terpineol mixtures (i.e., mixtures in which the main component is α-terpineol and which also contain β-terpineol or γ-terpineol).

[0041] The solvent may be used individually or in a mixture of two or more types. If the flux contains a solvent, the solvent content in the flux may be 5 to 50% by mass, 10 to 40% by mass, or 10 to 30% by mass, relative to the total mass of the flux.

[0042] <<Other Activating Agents>> Other activators include salicylic acid and organic acids other than monocarboxylic acid (B3), amines, halogen compounds, and organophosphorus compounds.

[0043] Other organic acids Other organic acids include, for example, carboxylic acids and organic sulfonic acids. Examples of carboxylic acids include aliphatic carboxylic acids, aromatic carboxylic acids, tricarboxylic acids, and hydroxycarboxylic acids. Examples of carboxylic acids include monocarboxylic acids and dicarboxylic acids. Examples of monocarboxylic acids include aliphatic monocarboxylic acids, aromatic monocarboxylic acids, and hydroxymonocarboxylic acids.

[0044] Examples of aliphatic carboxylic acids include aliphatic monocarboxylic acids and aliphatic dicarboxylic acids. Examples of aliphatic monocarboxylic acids include caproic acid, enanthic acid, caprylic acid, pelargonic acid, isoperargonic acid, capric acid, caproleic acid, lauric acid (dodecanoic acid), undecanoic acid, lindelic acid, tridecanoic acid, myristoleic acid, pentadecanoic acid, isopalmitic acid, palmitoleic acid, hyragonic acid, hydrocarpic acid, margaric acid, isostearic acid, elaidic acid, petroseric acid, molocinic acid, eleostearic acid, taliric acid, vaccenic acid, ricinoleic acid, vernolic acid, sterkric acid, nonadecanoic acid, eicosanoic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, myristic acid, glycolic acid, and thioglycolic acid. Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanediic acid, eicosanedioic acid, citraconic acid, diglycolic acid, tartaric acid, and 2,4-diethylglutaric acid.

[0045] Examples of aromatic carboxylic acids include aromatic monocarboxylic acids, aromatic hydroxymonocarboxylic acids, and aromatic dicarboxylic acids. Examples of aromatic monocarboxylic acids include benzoic acid, 3-hydroxybenzoic acid, picolinic acid, 3-hydroxypicolinic acid, parahydroxyphenylacetic acid, 2-quinolinecarboxylic acid, o-nitrobenzoic acid, m-nitrobenzoic acid, and p-nitrobenzoic acid. Examples of aromatic hydroxymonocarboxylic acids include 3-hydroxybenzoic acid, 3-hydroxypicolinic acid, parahydroxyphenylacetic acid, 2-hydroxybenzoic acid, and 4-hydroxybenzoic acid. Examples of aromatic dicarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, phenylsuccinic acid, dipicolinic acid, and dibutylaniline diglycolic acid.

[0046] Examples of tricarboxylic acids include citric acid and isocitric acid.

[0047] Examples of hydroxycarboxylic acids include aliphatic hydroxymonocarboxylic acids such as 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butanoic acid, and 2-hydroxyisobutyric acid; aromatic hydroxymonocarboxylic acids as described above; hydroxydicarboxylic acids such as malic acid and tartaric acid; and hydroxytricarboxylic acids such as citric acid and isocitric acid.

[0048] Other examples of carboxylic acids include tris(2-carboxyethyl) isocyanurate and 1,3-cyclohexanedicarboxylic acid.

[0049] Furthermore, polybasic carboxylic acids are another example of carboxylic acids. Examples of polybasic carboxylic acids include dimer acids, trimer acids, hydrogenated dimer acids (which are hydrogenated products of dimer acids), and hydrogenated trimer acids (which are hydrogenated products of trimer acids).

[0050] Examples of organic sulfonic acids include aliphatic sulfonic acids and aromatic sulfonic acids. Examples of aliphatic sulfonic acids include alkanesulfonic acids and alkanolsulfonic acids.

[0051] Other organic acids may be used individually or in mixtures of two or more types. If the flux contains other organic acids, the content of other organic acids in the flux may be greater than 0% by mass and 20% by mass or less, greater than 0% by mass and 10% by mass or less, greater than 0% by mass and 5% by mass or less, or greater than 0% by mass and 3% by mass or less, based on the total mass of the flux.

[0052] •amine Examples of amines include amino alcohols, azoles, guanidines, alkylamine compounds, and amine polyoxyalkylene adducts.

[0053] Examples of amino alcohols include N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, 1-amino-2-propanol, bis(2-hydroxypropyl)amine, and tris(2-hydroxypropyl)amine.

[0054] Examples of azoles include 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, and 1-cyanoethyl-2-ethylimidazole. Tyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl- s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanurate adduct, 2-phenylimidazole isocyanurate adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazole Phosphorus, 2,4-diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyl-s-triazine, epoxy-imidazole adduct, 2-methylbenzimidazole, 2-octylbenzimidazole, 2-pentylbenzimidazole, 2-(1-ethylpentyl)benzimidazole, 2-nonylbenzimidazole, 2-(4-thiazolyl)benzimidazole, benzimidazole, 1,2,4-triazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol], 6-(2-benzotriazolyl)-4-tert-octyl-6'-tert-butyl-4'-methyl-2,2'-methylenebisphenol, 1,2,3-benzotriazole Examples include 1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, carboxybenzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, 2,2'-[[(methyl-1H-benzotriazole-1-yl)methyl]imino]bisethanol, 1-(1',2'-dicarboxyethyl)benzotriazole, 1-(2,3-dicarboxypropyl)benzotriazole, 1-[(2-ethylhexylamino)methyl]benzotriazole, 2,6-bis[(1H-benzotriazole-1-yl)methyl]-4-methylphenol, 5-methylbenzotriazole, 5-phenyltetrazole, etc.

[0055] 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.

[0056] Examples of alkylamine compounds include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, and stearylamine.

[0057] An amine polyoxyalkylene adduct refers to an amine to which an alkylene oxide has been added. Examples of amine polyoxyalkylene adducts include terminal diamine polyalkylene glycols, aliphatic amine polyoxyalkylene adducts, aromatic amine polyoxyalkylene adducts, and polyvalent amine polyoxyalkylene adducts. Examples of alkylene oxides attached to amine polyoxyalkylene adducts include ethylene oxide, propylene oxide, and butylene oxide.

[0058] Terminal diamine polyalkylene glycols are compounds in which both ends of a polyalkylene glycol are aminated. Examples of terminally diamine polyalkylene glycols include terminally diamine polyethylene glycol, terminally diamine polypropylene glycol, and terminally diamine polyethylene glycol-polypropylene glycol copolymers. Examples of terminal diamine polyethylene glycol-polypropylene glycol copolymers include polyethylene glycol-polypropylene glycol copolymer bis(2-aminopropyl) ether and polyethylene glycol-polypropylene glycol copolymer bis(2-aminoethyl) ether.

[0059] Aliphatic amine polyoxyalkylene adducts, aromatic amine polyoxyalkylene adducts, and polyvalent amine polyoxyalkylene adducts are formed in which a polyoxyalkylene group is bonded to the nitrogen atom of an amine. Examples of such amines include ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, hexamethylenediamine, diethylenetriamine, laurylamine, stearylamine, oleylamine, tallowamine, hydrogenated tallowamine, tallowpropyldiamine, metaxyldiamine, tolylenediamine, paraxyldiamine, phenylenediamine, isophoronediamine, 1,10-decanediamine, 1,12-dodecanediamine, 4,4-diaminodicyclohexylmethane, 4,4-diaminodiphenylmethane, butane-1,1,4,4-tetraamine, pyrimidine-2,4,5,6-tetraamine, and the like.

[0060] Amines may be used individually or in mixtures of two or more types. The amine is preferably an amine polyoxyalkylene adduct, and more preferably a terminal diamine polyalkylene glycol.

[0061] If the flux contains amines, the amine content in the flux may be 5% by mass or more and 70% by mass or less, 10% by mass or more and 60% by mass or less, or 20% by mass or more and 50% by mass or less, based on the total mass of the flux. If the amine content in the flux is within the preferred range described above, it becomes easier to improve the heat resistance of the flux, and even after prolonged preheating at high temperatures, the flux is more easily maintained in the applied area, thereby improving bonding reliability. In addition, it becomes easier to suppress the decrease in flux activity caused by the reaction between amines and organic acids during preheating. If the amine content in the flux is above the lower limit of the preferred range mentioned above, the heat resistance of the flux is more easily increased, and the flux is more easily maintained in the applied area even after preheating at high temperatures for a long time, thereby improving bonding reliability. If the amine content in the flux is below the upper limit of the preferred range mentioned above, it becomes easier to suppress the reaction between the amine and the organic acid during preheating, which would otherwise reduce the flux's activity.

[0062] • Halogen compounds Examples of halogen compounds include amine hydrohalides and organic halogen compounds other than amine hydrohalides. Amine hydrohalides are compounds formed by reacting an amine with a hydrogen halide. Examples of amines used here include those mentioned above in the section on [amines]. The flux according to this embodiment may or may not contain halogen compounds.

[0063] Halogen compounds may be used individually or in mixtures of two or more types. If the flux contains halogen compounds, the amount of halogen compounds in the flux may be greater than 0% by mass and 3% by mass or less, greater than 0% by mass and 2% by mass or less, or greater than 0% by mass and 1% by mass or less, relative to the total mass of the flux.

[0064] If the flux contains other activators, the content of other activators in the flux may be 5% by mass or more and 70% by mass or less, 10% by mass or more and 60% by mass or less, or 20% by mass or more and 50% by mass or less, based on the total mass of the flux.

[0065] • Surfactants Examples of surfactants include nonionic surfactants. Examples of nonionic surfactants include polyoxyalkylene adducts. Examples of alkylene oxides derived from polyoxyalkylene adducts include ethylene oxide, propylene oxide, and butylene oxide. Examples of polyoxyalkylene adducts include polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol copolymer, ethylene oxide-resorcinol copolymer, polyoxyalkylene acetylene glycols, polyoxyalkylene glyceryl ether, polyoxyalkylene alkyl ether, polyoxyalkylene ester, and polyoxyalkylene alkylamide. Alternatively, nonionic surfactants include polyoxyalkylene adducts of alcohols. Examples of such alcohols include aliphatic alcohols, aromatic alcohols, and polyhydric alcohols.

[0066] Examples of polyoxyalkylene glyceryl ethers include compounds represented by the following general formula (su0) (SU0).

[0067] [ka] [In the formula, R a1 , R a2 and R a3 Each of these is an organic group, independently of the others. However, R a1 , R a2 and R a3 At least one of them has an oxyalkylene group. a1 , R a2 and R a3 In this case, the total number of repeating oxyalkylene groups is 15 to 120.

[0068] R a1 , R a2 and R a3 Examples of organic groups in this context include hydrocarbon groups that may have substituents. Examples of hydrocarbon groups include chain-like hydrocarbon groups or cyclic hydrocarbon groups.

[0069] The chain-like hydrocarbon group can be linear or branched. The chain-like hydrocarbon group may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. Some or all of the hydrogen atoms in a chain of hydrocarbon groups may be substituted with a monovalent group containing a heteroatom. Examples of such monovalent groups include halogen atoms, nitro groups, amino groups, hydroxyl groups, carboxyl groups, nitrile groups, and thiol groups. The methylene groups in a chain of hydrocarbon groups may be substituted with a divalent group containing a heteroatom. Examples of such divalent groups include carbonyl groups, -O-, -C(=O)-O-, -OC(=O)-, amide groups, and imino groups.

[0070] The cyclic hydrocarbon group may be an aliphatic hydrocarbon group, an aromatic hydrocarbon group, a polycyclic group, or a monocyclic group.

[0071] R a1 , R a2 and R a3Examples of oxyalkylene groups that may be present include oxyethylene groups, oxypropylene groups, and oxybutylene groups.

[0072] R a1 , R a2 and R a3 In this, the total number of repeating oxyalkylene groups is preferably 20 to 100, more preferably 25 to 80, and even more preferably 40 to 80.

[0073] The compound (SU0) is preferably the compound (SU0-1) represented by the following general formula (su0-1).

[0074] [ka] [In the formula, R a11 , R a12 , R a13 , R b11 , R b12 and R b13 Each of these independently represents -C2H4- or -CH2-CH(CH3)-. n11, n12, n13, m11, m12, and m13 are non-negative integers. 15 ≤ n11 + n12 + n13 + m11 + m12 + m13 ≤ 120. p11, p12, p13, q11, q12, and q13 are each independently integers between 1 and 18 (inclusive).

[0075] n11, n12, and n13 are each preferably integers between 0 and 18, more preferably integers between 0 and 10, even more preferably integers between 0 and 5, and particularly preferably 0.

[0076] p11, p12, and p13 are each preferably integers between 6 and 15, more preferably between 8 and 12, and even more preferably 10.

[0077] q11, q12, and q13 are each preferably integers between 2 and 10, more preferably between 3 and 8, and even more preferably 5.

[0078] R b11 , R b12 and R b13 -C2H4- is preferred. For n11, n12, n13, m11, m12, and m13, it is preferable that 20 ≤ n11 + n12 + n13 + m11 + m12 + m13 ≤ 100, more preferably that 25 ≤ n11 + n12 + n13 + m11 + m12 + m13 ≤ 80, and even more preferably that 40 ≤ n11 + n12 + n13 + m11 + m12 + m13 ≤ 80.

[0079] In the above general formula (su0-1), preferably, n11, n12, and n13 are each independent integers between 0 and 18, inclusive; p11, p12, and p13 are each independent integers between 6 and 15, inclusive; q11, q12, and q13 are each independent integers between 2 and 10; R b11 , R b12 and R b13 This represents -C2H4- or -CH2-CH(CH3)-; 20 ≤ n11 + n12 + n13 + m11 + m12 + m13 ≤ 100.

[0080] In the above general formula (su0-1), more preferably, n11, n12, and n13 are each independent integers between 0 and 10 (inclusive); p11, p12, and p13 are each independent integers between 8 and 12; q11, q12, and q13 are each independent integers between 3 and 8, inclusive; R b11 , R b12 and R b13 It is -C2H4-; 25 ≤ n11 + n12 + n13 + m11 + m12 + m13 ≤ 80.

[0081] In the above general formula (su0-1), more preferably, n11, n12, and n13 are each independent integers between 0 and 5 (inclusive); p11, p12, and p13 are each independent integers between 8 and 12; q11, q12, and q13 are each independent integers between 3 and 8, inclusive; R b11 , R b12 and R b13 It is -C2H4-; 25 ≤ n11 + n12 + n13 + m11 + m12 + m13 ≤ 80.

[0082] In the above general formula (su0-1), particularly preferably, n11, n12, and n13 are each independently 0; p11, p12, and p13 are each independent integers between 8 and 12; q11, q12, and q13 are each independent integers between 3 and 8, inclusive; R b11 , R b12 and R b13 It is -C2H4-; 25 ≤ n11 + n12 + n13 + m11 + m12 + m13 ≤ 80.

[0083] In the above general formula (su0-1), most preferably, n11, n12, and n13 are each independently 0; p11, p12, and p13 are each independent integers between 8 and 12; q11, q12, and q13 are each independent integers between 3 and 8, inclusive; R b11 , R b12 and R b13 It is -C2H4-; 40 ≤ n11 + n12 + n13 + m11 + m12 + m13 ≤ 80.

[0084] Compound (SU0) may be used individually or as a mixture of two or more types.

[0085] If the flux contains compound (SU0), the content of compound (SU0) in the flux is preferably 0.2 to 4% by mass, and more preferably 0.3 to 2% by mass, relative to the total mass of the flux. If the content of compound (SU0) is within the aforementioned preferred range, the heat resistance of the flux is more easily improved, and even after prolonged preheating at high temperatures, the flux is more easily maintained in the applied area, thereby improving bonding reliability. Furthermore, even after prolonged preheating at high temperatures, it becomes easier to suppress the flux from wetting and spreading beyond the applied area onto the substrate. If the content of compound (SU0) is above the lower limit of the preferred range mentioned above, the heat resistance of the flux is more easily improved, and even after preheating at high temperatures for a long time, the flux is more easily maintained in the applied area, thereby improving bonding reliability. If the content of compound (SU0) is below the upper limit of the preferred range described above, it becomes easier to suppress the flux from wetting and spreading beyond the coated area onto the substrate, even when preheating at high temperatures for a long time.

[0086] If the flux contains a nonionic surfactant, the content of the nonionic surfactant in the flux is preferably 0.3 to 70% by mass, more preferably 5 to 50% by mass or less, and even more preferably 10 to 40% by mass or less, based on the total mass of the flux.

[0087] When the flux contains compound (SU0) as a nonionic surfactant, the proportion of compound (SU0) in the flux is expressed as a mass ratio of compound (SU0) / nonionic surfactant, with the nonionic surfactant content being 100% by mass, preferably 0.2 to 50% by mass, more preferably 0.5 to 20% by mass, and even more preferably 0.5 to 10% by mass. If the mass ratio expressed as compound (SU0) / nonionic surfactant is within the aforementioned preferred range, the heat resistance of the flux is more easily improved, and even after prolonged preheating at high temperatures, the flux is more easily maintained in the applied area, thereby improving bonding reliability. Furthermore, even after prolonged preheating at high temperatures, it becomes easier to suppress the flux from wetting and spreading beyond the applied area onto the substrate. If the mass ratio expressed as compound (SU0) / nonionic surfactant is above the lower limit of the preferred range described above, the heat resistance of the flux is more easily improved, and the flux is more easily maintained in the applied area even after preheating at high temperatures for a long time, thereby improving bonding reliability. If the mass ratio expressed as compound (SU0) / nonionic surfactant is below the upper limit of the preferred range described above, it becomes easier to suppress the flux from wetting and spreading beyond the coated area onto the substrate, even when preheating at high temperatures for a long time.

[0088] If the flux contains a nonionic surfactant or an amine polyoxyalkylene adduct, the total content of the nonionic surfactant and the amine polyoxyalkylene adduct in the flux is preferably 20% to 80% by mass, and more preferably 30% to 70% by mass, based on the total mass of the flux. If the total content of nonionic surfactant and amine polyoxyalkylene adduct in the flux is within the preferred range described above, the heat resistance of the flux can be easily increased, and the flux can be more easily maintained in the coated area even after preheating at high temperatures for a long time, thereby improving bonding reliability. In addition, the separation of nonionic surfactant in the flux can be easily suppressed. If the total content of nonionic surfactant and amine polyoxyalkylene adduct in the flux is above the lower limit of the preferred range described above, the heat resistance of the flux is more easily increased, and the flux is more easily maintained in the applied area even after preheating at high temperatures for a long time, thereby improving bonding reliability. If the total content of nonionic surfactant and amine polyoxyalkylene adduct in the flux is below the upper limit of the preferred range mentioned above, the separation of nonionic surfactant in the flux becomes easier to suppress.

[0089] The ratio of the compound (SU0) content to the total content of the nonionic surfactant and amine polyoxyalkylene adduct in the flux is preferably 0.1 to 20% by mass, and more preferably 0.2 to 10% by mass, expressed as the mass ratio of compound (SU0) / (nonionic surfactant and amine polyoxyalkylene adduct), with the total content of the nonionic surfactant and amine polyoxyalkylene adduct being 100% by mass. If the mass ratio of compound (SU0) / (nonionic surfactant and amine polyoxyalkylene adduct) is within the preferred range described above, the heat resistance of the flux is more easily improved, and even after prolonged preheating at high temperatures, the flux is more easily maintained in the applied area, thereby improving bonding reliability. Furthermore, even after prolonged preheating at high temperatures, it becomes easier to suppress the flux from wetting and spreading beyond the applied area onto the substrate. If the mass ratio of compound (SU0) / (nonionic surfactant and amine polyoxyalkylene adduct) is above the lower limit of the preferred range described above, the heat resistance of the flux is more easily improved, and the flux is more easily maintained in the applied area even after preheating at high temperatures for a long time, thereby improving bonding reliability. If the mass ratio represented by compound (SU0) / (nonionic surfactant and amine polyoxyalkylene adduct) is below the upper limit of the preferred range described above, it becomes easier to suppress the flux from wetting and spreading beyond the coated area onto the substrate, even when preheating at high temperatures for a long time.

[0090] ≪Thixotropic agents≫ Examples of thixotropic agents include ester-based thixotropic agents, amide-based thixotropic agents, and sorbitol-based thixotropic agents. The flux according to this embodiment may or may not contain a thixotropic agent, and it is preferable that it does not contain one. Thixopropyl alcohol may be used individually or in combination of two or more types.

[0091] If the flux contains a thixotropic agent, the amount of the thixotropic agent in the flux may be greater than 0% by mass and 1% by mass or less, greater than 0% by mass and 0.5% by mass or less, greater than 0% by mass and 0.3% by mass or less, or greater than 0% by mass and 0.1% by mass or less, relative to the total mass of the flux.

[0092] ≪Resin components≫ The flux according to this embodiment may or may not contain a resin component, and it is preferable that it does not contain a resin component. In this specification, examples of resin components include rosin, resins other than rosin, and the like.

[0093] In this specification, "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). 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 esters, acid-modified hydrogenated rosin, acid-modified hydrogenated rosin, acid-modified disproportionated rosin, acid-modified disproportionated rosin, phenol-modified rosin, and α,β-unsaturated carboxylic acid modified products (acrylic rosin, maleated rosin, fumarated rosin, etc.), as well as purified, hydrated and disproportionated products of the polymerized rosin, and purified, hydrated 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, acid-modified rosin soap, and the like.

[0094] Examples of resins other than rosin include terpene resins, modified terpene resins, terpene phenol resins, modified terpene phenol resins, styrene resins, modified styrene resins, xylene resins, modified xylene resins, acrylic resins, polyethylene resins, acrylic-polyethylene copolymer resins, and other thermosetting resins. Examples of modified terpene resins include aromatic modified terpene resins, hydrogenated terpene resins, and hydrogenated aromatic modified terpene resins. Examples of modified terpene phenol resins include hydrogenated terpene phenol resins. Examples of modified styrene resins include styrene acrylic resins and styrene maleic acid resins. Examples of modified xylene resins include phenol modified xylene resins, alkylphenol modified xylene resins, phenol modified resol-type xylene resins, polyol modified xylene resins, and polyoxyethylene-added xylene resins.

[0095] Other thermosetting resins include, for example, epoxy resins. Examples of epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, glycidylamine type resin, alicyclic epoxy resin, aminopropane type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, anthracene type epoxy resin, triazine type epoxy resin, dicyclopentadiene type epoxy resin, triphenylmethane type epoxy resin, fluorene type epoxy resin, phenol aralkyl type epoxy resin, and novolac type epoxy resin.

[0096] If the flux contains a resin component, the resin component content in the flux may be greater than 0% by mass and 3% by mass or less, greater than 0% by mass and 2% by mass or less, greater than 0% by mass and 1% by mass or less, greater than 0% by mass and 0.3% by mass or less, or greater than 0% by mass and 0.1% by mass or less, relative to the total mass of the flux. It is preferable that the flux does not contain a resin component.

[0097] In the flux, the rosin content may be 0% to 3% by mass or 0% to 1% by mass relative to the total mass of the flux. It is preferable that the flux does not contain rosin.

[0098] ·Metal deactivator In this context, "metal deactivator" refers to a compound that has the property of preventing metal degradation upon contact with certain compounds. Examples of metal deactivators include hindered phenol compounds and nitrogen compounds. The flux according to this embodiment may or may not contain a metal deactivator.

[0099] Hindered phenol compounds are phenol compounds that have a bulky substituent (for example, a branched or cyclic alkyl group such as a t-butyl group) at at least one of the ortho positions of the phenol. The hindered phenol compounds are not particularly limited and include, for example, bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylenebis(oxyethylene)], N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], 1,6-hexanediolbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 2,2'-dihydroxy-3,3'-bis Su(α-methylcyclohexyl)-5,5'-dimethyldiphenylmethane, 2,2'-methylenebis(6-tert-butyl-p-cresol), 2,2'-methylenebis(6-tert-butyl-4-ethylphenol), triethylene glycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,4-bis Su-(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, pentaerythrityl-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2-thio-diethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-hexameth Examples include lenbis(3,5-di-t-butyl-4-hydroxyhydrocinnamamide), 3,5-di-tert-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxamide, and compounds represented by the following chemical formulas.

[0100] [ka] (In the formula, Z is an alkylene group that may be substituted. 81and R 82 Each of these is independently an alkyl group, aralkyl group, aryl group, heteroaryl group, cycloalkyl group, or heterocycloalkyl group, which may be substituted. 83 and R 84 These are, independently, alkyl groups that may be substituted.

[0101] Examples of nitrogen compounds used as metal deactivators include hydrazide-based nitrogen compounds, amide-based nitrogen compounds, triazole-based nitrogen compounds, and melamine-based nitrogen compounds.

[0102] Examples of hydrazide nitrogen compounds include any nitrogen compound having a hydrazide skeleton, such as bis[N2-(2-hydroxybenzoyl)hydrazide] dodecanediate, N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, disalithyroyl hydrazide decanedicarboxylic acid, N-salicylidene-N'-salicyl hydrazide, m-nitrobenzhydrazide, 3-aminophthalhydrazide, phthalate dihydrazide, adipic acid hydrazide, oxalobis(2-hydroxy-5-octylbenzylidene hydrazide), N'-benzoylpyrrolidone carboxylic acid hydrazide, and N,N'-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hydrazine.

[0103] Any nitrogen compound having an amide skeleton can be used, such as N,N'-bis{2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxyl]ethyl}oxamide.

[0104] Triazole nitrogen compounds can be any nitrogen compounds having a triazole skeleton, such as N-(2H-1,2,4-triazole-5-yl)salicylamide, 3-amino-1,2,4-triazole, and 3-(N-salicyloyl)amino-1,2,4-triazole.

[0105] Any nitrogen compound having a melamine skeleton can be used, such as melamine and melamine derivatives. More specifically, examples include trisaminotriazine, alkylated trisaminotriazine, alkoxyalkylated trisaminotriazine, melamine, alkylated melamine, alkoxyalkylated melamine, N2-butylmelamine, N2,N2-diethylmelamine, and N,N,N',N',N'',N''-hexakis(methoxymethyl)melamine.

[0106] The metal deactivator may be used alone or in a mixture of two or more types. If the flux contains a metal deactivator, the content of the metal deactivator in the flux may be greater than 10% by mass or less, greater than 0% by mass or less, greater than 5% by mass or less, greater than 0% by mass or less, or greater than 1% by mass or less, based on the total mass of the flux.

[0107] • Antioxidant Examples of antioxidants include hindered phenol-based antioxidants such as 2,2'-dihydroxy-3,3'-bis(α-methylcyclohexyl)-5,5'-dimethyldiphenylmethane.

[0108] Antioxidants may be used individually or in combination of two or more types. If the flux contains an antioxidant, the amount of antioxidant in the flux may be greater than 0% by mass and 10% by mass or less, greater than 0% by mass and 5% by mass or less, greater than 0% by mass and 3% by mass or less, or greater than 0% by mass and 1% by mass or less, relative to the total mass of the flux.

[0109] • Silane coupling agent Examples of silane coupling agents include those known to those skilled in the art. Silane coupling agents may be used individually or in mixtures of two or more types. If the flux contains a silane coupling agent, the amount of the silane coupling agent in the flux may be greater than 0% by mass and 5% by mass or greater than 0% by mass and 3% by mass or less, based on the total mass of the flux.

[0110] • Colorants Examples of coloring agents include those known to those skilled in the art. The coloring agent may be used alone or in a mixture of two or more types. If the flux contains a coloring agent, the amount of coloring agent in the flux may be greater than 0% by mass and less than or equal to 10% by mass, or greater than 0% by mass and less than or equal to 5% by mass, relative to the total mass of the flux.

[0111] The flux according to this embodiment, as described above, has enhanced heat resistance due to the inclusion of monocarboxylic acid (B3) and salicylic acid. Salicylic acid and monocarboxylic acid (B3) are compounds containing a benzene ring, and they tend to maintain their activity as activators even after prolonged preheating at high temperatures. In salicylic acid, the hydroxyl group and carboxyl group are located proximal to each other, and their chelating activity protects the metal surface being bonded. This suppresses the reaction between the activator in the flux and the metal surface, making it easier to maintain the activity of the activator. In monocarboxylic acids (B3), two hydroxyl groups are located near the carboxyl group, resulting in a strong chelating effect that protects the metal surface of the object being bonded. In monocarboxylic acids (B3), the hydroxyl group adjacent to the carboxyl group attempts to abstract a proton from the carboxyl group, thereby increasing the activity of the monocarboxylic acid (B3). When a monocarboxylic acid (B3) has hydroxyl groups at positions 2 and 6 of the benzene ring, the presence of two hydroxyl groups adjacent to the carboxyl group makes it easier for the proton to be removed from the carboxyl group, thereby increasing the activity of the monocarboxylic acid (B3). When a monocarboxylic acid (B3) has hydroxyl groups at the 2nd and 3rd positions of the benzene ring, the interaction between these hydroxyl groups makes it easier for the protons of these hydroxyl groups to be removed, thus making it easier for the monocarboxylic acid (B3) to coordinate to the metal surface. As a result, the reaction between the activator contained in the flux and the metal surface is further suppressed, and the activity of the activator is more easily maintained. When the monocarboxylic acid (B3) has hydroxyl groups at the 2nd position and either the 4th or 5th position of the benzene ring, the heat resistance is enhanced by the balance of the effects described above. The synergistic effect described above enhances the heat resistance of the flux.

[0112] Alternatively, from another perspective, the following embodiments are also preferable. <1> A flux containing an organic acid, an amine, a nonionic surfactant, and a solvent, wherein the organic acid includes a monocarboxylic acid (B3) and salicylic acid represented by the following general formula (b3), and the amine includes an amine polyoxyalkylene adduct.

[0113] [ka] [In the formula, nb31 is an integer between 1 and 4 (inclusive).]

[0114] <2> In the above general formula (b3), nb31 is 1. <1> The flux described above. <3> The aforementioned nonionic surfactant contains a compound (SU0) represented by the following general formula (su0): <1> or <2> The flux described above.

[0115] [ka] [In the formula, R a1 , R a2 and R a3 Each of these is an organic group, independently of the others. However, R a1 , R a2 and R a3 One or more selected from the group consisting of have an oxyalkylene group. a1 , Ra2 and R a3 In this case, the total number of repeating oxyalkylene groups is 15 to 120.

[0116] <4> The total content of the salicylic acid and the monocarboxylic acid (B3) is 10% by mass or more relative to the total mass of the flux. <1> ~ <3> The flux described in any one of the following lists. <5> The content of the aforementioned compound (SU0) is 0.2 to 4% by mass relative to the total mass of the flux. <3> The flux described above. <6> The total content of the nonionic surfactant and the amine polyoxyalkylene adduct is preferably 20% by mass or more and 80% by mass or less, relative to the total mass of the flux. <1> ~ <5> The flux described in any one of the following lists. <7> The rosin content is 0-1% by mass relative to the total mass of the flux. <1> ~ <6> The flux described in any one of the following lists. <8> It is for heat-compression soldering. <1> ~ <7> The flux described in any one of the following lists.

[0117] (Solder paste) The solder paste of this embodiment contains solder alloy powder and the flux described above.

[0118] As the solder alloy, solder alloys of known compositions can be used. The solder alloy may consist of elemental Sn solder, or Sn-Ag, Sn-Cu, Sn-Ag-Cu, Sn-Bi, Sn-In, etc., or solder alloys to which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. are added. The solder alloy may consist of a Sn-Pb system, or a solder alloy in which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. are added to the Sn-Pb system. A solder alloy that does not contain lead (Pb) is preferred.

[0119] Flux content: The flux content in the solder paste is preferably 5 to 30% by mass, and more preferably 5 to 15% by mass, relative to the total mass of the solder paste.

[0120] According to the solder paste of the embodiment described above, it is possible to improve the heat resistance of the solder paste by including the flux according to the embodiment.

[0121] (Method of manufacturing the joint) The method for manufacturing a joined body according to this embodiment includes the step of obtaining a joined body by heat-pressing and soldering a component on which solder balls are placed to the soldering surface of a substrate treated with the flux according to the above embodiment. The method for manufacturing the bonded body according to this embodiment will be explained by illustrating a method that includes a flux coating step, a preheating step, and a thermocompression bonding step. In this manufacturing method, a substrate 10 with lands 11 arranged on it, as shown in Figure 1, and a component 20 on which solder balls 21 are placed, as shown in Figure 2, are prepared.

[0122] <Flux application process> The flux application process will be explained with reference to Figure 1. In this process, flux 12 is applied to the substrate 10 on which the lands 11 are arranged, so as to cover the lands 11. As a result, the lands 11 are covered with flux 12, as shown in Figure 1. Here, the soldering surface of the substrate 10 is the land 11.

[0123] Examples of the substrate 10 include printed circuit boards. The flux 12 used is the flux according to the above embodiment. Examples of flux application devices include spray fluxers. Among these, spray fluxers are preferred from the viewpoint of stable application amount. The amount of flux applied should be 5 to 180 mL / m² from the perspective of solderability. 2 Preferably, it is 10-150 mL / m²2 It is more preferable that the concentration be 15-120 mL / m². 2 It is particularly preferable that this be the case.

[0124] <Preheating process> In the preheating step, the substrate 10 that has been treated with flux 12 in the flux coating step is preheated. In the preheating process, the temperature at which the substrate 10 is heated is preferably 100 to 300°C, and more preferably 150 to 250°C. The atmospheric pressure during preheating may normally be atmospheric pressure. A N2 atmosphere is preferred during preheating, and the oxygen concentration is preferably 10,000 ppm or less. The preheating time is preferably 5 minutes to 2 hours, and more preferably 10 minutes to 1 hour.

[0125] <Thermocompression bonding process> In the thermocompression bonding process, as shown in Figure 3, the component 20 and the substrate 10 (after preheating) on ​​which the lands 11 are arranged are positioned so that the lands 11 and the solder balls 21 face each other.

[0126] Next, as shown in Figure 4, by applying pressure in the direction of the arrow in Figure 4 using the bonding head 30, the solder balls 21 on the component 20 and the bonding surface (land 11) on the substrate 10 are heat-compressed together to obtain a bonded body.

[0127] For thermocompression bonding, the temperature at which the component 20 is heated is, for example, 250 to 320°C, and preferably 280 to 300°C. The atmospheric pressure during heat sealing can usually be atmospheric pressure. The atmosphere during preheating is preferably an N2 atmosphere, with an oxygen concentration of 100 ppm or less. The bonding pressure during thermocompression bonding is not particularly limited as long as the components and substrate being bonded are not damaged, and can be set appropriately by those skilled in the art.

[0128] According to the method for manufacturing the bonded body of this embodiment described above, by using the flux 12 of the embodiment, which has improved heat resistance, it is possible to improve the reliability of the bond between the substrate 10 and the component 20. [Examples]

[0129] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0130] <Preparation of flux> (Examples 1-4, Comparative Examples 1-5) Fluxes for the examples and comparative examples were prepared with the compositions shown in Tables 1-3. The components of the raw materials used are shown below. The content in Tables 1-2 is in mass percent when the total mass of the flux is set to 100% by mass, and a blank space means 0% by mass.

[0131] As monocarboxylic acid (B3), 2,3-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, and 2,6-dihydroxybenzoic acid were used. 2,3-Dihydroxybenzoic acid is a compound represented by the following chemical formula (b3-1), and its CAS number is 303-38-8. 2,5-Dihydroxybenzoic acid is a compound represented by the following chemical formula (b3-2), and its CAS number is 490-79-9. 2,6-Dihydroxybenzoic acid is a compound represented by the following chemical formula (b3-3), and its CAS number is 303-07-1.

[0132] [ka]

[0133] As comparative compounds that do not fall under the category of monocarboxylic acid (B3), 3-hydroxybenzoic acid, 3,5-dihydroxybenzoic acid, and 3,4,5-dihydroxybenzoic acid were used. 3-Hydroxybenzoic acid is a compound represented by the following chemical formula (b-c1). 3,5-Dihydroxybenzoic acid is a compound represented by the following chemical formula (b-c2). 3,4,5-Dihydroxybenzoic acid is a compound represented by the following chemical formula (b-c3).

[0134] [ka]

[0135] As the amine, an amine polyoxyalkylene adduct was used. More specifically, as the amine polyoxyalkylene adduct, O,O'-bis(2-aminopropyl)polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol, a terminal diamine polyethylene glycol-polypropylene glycol copolymer, was used. The CAS number of this compound is 65605-36-9.

[0136] As nonionic surfactants, the compound (SUO-1-2) and the resorcinol ethylene oxide adduct were used. Compound (SUO-1-2) is a compound in which a+b+c=60 in the following chemical formula (SUO-1-0).

[0137] [ka]

[0138] Dipropylene glycol monomethyl ether was used as the solvent.

[0139] The following evaluation methods were used to evaluate solder wettability (wetting speed) and flux retention.

[0140] <Evaluation of solder wettability (wetting speed)> Solder wettability was evaluated in accordance with JIS Z 3198-4 using the following method. A circuit board with solder bumps formed on the main body was prepared. The dimensions of the main body of the circuit board were 30mm x 50mm x 1.0mm. The composition of the main body of the circuit board was glass epoxy resin (grade: FR-4). The size of the solder bumps was 1.5mm x 1.5mm. The composition of the solder bumps was Sn-3Ag-0.5Cu (each value is in mass%). The pitch of the solder bumps was 3.2mm.

[0141] 0.05 g of flux from each of Examples 1-3 and Comparative Examples 1-5 was applied to the substrate. The substrate was placed on a hot plate heated to 220°C for 30 minutes. The step of heating at 220°C for 30 minutes corresponds to the preheating step. Next, the test specimen (a copper plate heat-treated at 150°C for 1 hour) was immersed in the flux on the substrate.

[0142] Next, the solder wettability of the test specimen was evaluated using the wetting balance method. A Solder Checker SAT-5100 (manufactured by RHESCA) was used as the test apparatus, and Sn-3Ag-0.5Cu (each value is in mass%) was used as the solder. Next, under the following test conditions, the test specimens immersed in flux were immersed in a solder bath containing molten solder, and the zero-cross time (sec) was obtained. Subsequently, five measurements were taken for each flux in Examples 1-3 and Comparative Examples 1-5, and the average of the five obtained zero-cross times (sec) was calculated. The evaluation results are shown in Tables 1 and 2. A shorter average zero-cross time (sec) indicates a higher wetting speed and better solder wettability, i.e., superior heat resistance. If the test piece did not wet at all, it was marked as "NG".

[0143] The test conditions were set as follows: Immersion speed in solder bath: 10 mm / sec Immersion depth in solder bath: 2.0 mm Immersion time in solder bath: 10 seconds Solder bath temperature: 250℃

[0144] <Evaluation of flux retention> (1) Evaluation method The fluxes from Example 1 and Example 4 were applied to the flux-coated area of ​​a glass epoxy substrate (size 105 mm x 105 mm, substrate material: glass epoxy). The flux-coated substrate was then heated at 220°C for 30 minutes. The flux retention of the substrate after heating was evaluated according to the following criteria. The evaluation results are shown in Table 3.

[0145] (2) Judgment criteria In the area where flux A was applied, there were no areas where the flux was not maintained and there were no areas where the flux was missing (i.e., areas where the substrate surface was exposed), indicating good performance. In the area where flux B was applied, there were areas where the flux was not maintained and there were areas where the flux was missing (i.e., areas where the substrate surface was exposed), which is a defect.

[0146] [Table 1]

[0147] As shown in Table 1, Example 1, which contained both monocarboxylic acid (B3) and salicylic acid, had superior solder wettability, i.e., superior heat resistance, compared to Comparative Examples 1 and 2, which contained only one of either monocarboxylic acid (B3) or salicylic acid.

[0148] [Table 2]

[0149] As shown in Table 2, Examples 1-3, which contained both monocarboxylic acid (B3) and salicylic acid, exhibited superior solder wettability, and therefore superior heat resistance, compared to Comparative Examples 3-5, which contained salicylic acid but did not contain monocarboxylic acid (B3).

[0150] [Table 3]

[0151] As shown in Table 3, Example 1, which contained compound (SU0), showed superior flux retention compared to Example 4, which did not contain compound (SU0). [Industrial applicability]

[0152] The flux of the present invention can be suitably used for thermocompression bonding a ball grid array to a substrate by thermocompression bonding. [Explanation of Symbols]

[0153] 10 PCBs, 11 pads, 12 flux, 20 components, 21 solder balls, 30 bonding heads

Claims

1. It contains a monocarboxylic acid (B3) represented by the following general formula (b3) and salicylic acid, The content of the monocarboxylic acid (B3) is 5 to 20% by mass. The flux has a salicylic acid content of 5 to 20% by mass. 【Chemistry 1】 [In the formula, nb31 is 1.]

2. Furthermore, it contains a compound (SU0) represented by the following general formula (SU0), The flux according to claim 1, wherein the content of the compound (SU0) is 0.2 to 4% by mass. 【Chemistry 2】 [Wherein, R ａ１ , R ａ２ and R ａ３ are each independently an organic group. However, one or more selected from the group consisting of R ａ１ , R ａ２ and R ａ３ have an oxyalkylene group. The total number of repetitions of the oxyalkylene group in R ａ１ , R ａ２ and R ａ３ is 15 to 120.]

3. Furthermore, it contains an amine polyoxyalkylene adduct, The flux according to claim 1, wherein the content of the amine polyoxyalkylene adduct is 5% by mass or more and 70% by mass or less.

4. The flux according to claim 1, wherein the total content of the salicylic acid and the monocarboxylic acid (B3) is 10% by mass or more with respect to the total mass of the flux.

5. The flux according to claim 1, wherein the rosin content is 0 to 1% by mass relative to the total mass of the flux.

6. The flux according to claim 1, for use in thermocompression soldering.

7. Solder paste comprising the flux according to any one of claims 1 to 6 and solder powder.

8. A method for manufacturing a joint, comprising the step of obtaining a joint by thermally pressing and soldering a soldering surface of a substrate treated with the flux described in any one of claims 1 to 6 and a component on which solder balls are placed.

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