Method for manufacturing flux, solder paste, and bonded products

Abstract

Even if preheating is performed at a high temperature for a long time, a flux that is maintained in the area where the flux is applied and enhances bonding reliability, a solder paste containing the flux, and a method for manufacturing a bonded body using the flux are provided. 【Solution means】A flux containing a nonionic surfactant, an organic acid, and a solvent is employed. The nonionic surfactant includes a compound (SU0) represented by the general formula (su0). In the formula, 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 repeating units of the oxyalkylene group in R a1 , R a2 and R a3 is 15 to 120. [Chemical formula 1] TIFF0007862753000016.tif39170

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 from the metal surfaces of the objects to be soldered and from 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, making them prone to warping during reflow soldering. In contrast, a thermocompression bonding method is adopted for joining thin components and substrates (for example, Non-Patent Document 1).

[0006] The joining by thermocompression bonding will be described by exemplifying FIGS. 1 to 4. 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 a 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 a 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 joining by thermocompression bonding, 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 thermocompression bonding is performed to obtain a joined body.

Prior Art Documents

Non-Patent Documents

[0008]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] In thermal compression bonding as shown in FIG. 4, since the heating time is limited, the substrate coated with flux may be preheated at a high temperature for a long time (for example, 30 minutes at 220°C). The inventors have found that when a substrate coated with a conventional flux is preheated at a high temperature for a long time, there is a problem that the flux is not maintained in the region where the flux is applied, and a portion where the flux is missing (that is, a portion where the substrate surface is exposed) occurs. In such a region where the flux is missing, poor bonding between the substrate and the component is likely to occur.

[0010] The present invention has been made in view of the above circumstances, and an object thereof is to provide a flux that can be maintained in the region where the flux is applied and enhance the bonding reliability even when preheated at a high temperature for a long time, a solder paste containing the flux, and a method for manufacturing a bonded body using the flux.

Means for Solving the Problems

[0011] The present invention includes the following aspects. [1] A flux containing a nonionic surfactant, an organic acid, and a solvent, wherein the nonionic surfactant includes a compound (SU0) represented by the following general formula (su0).

[0012] <​​​​​​​​​​​​​​​​​​​​​​​​​​[2] The flux described in [1], wherein the compound (SU0) is the compound (SU0-1) represented by the following general formula (su0-1).

[0014] [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).

[0015] [3] The flux according to [1] or [2], wherein the content of the compound (SU0) is 0.2 to 4% by mass with respect to the total mass of the flux. [4] The flux according to any one of [1] to [3] further contains an amine polyoxyalkylene adduct. [5] The flux according to [4], wherein the total content of the nonionic surfactant other than the compound (SU0) and the amine polyoxyalkylene adduct is 30% by mass or more with respect to the total mass of the flux.

[0016] [6] The flux according to any one of [1] to [5], wherein the organic acid comprises a monocarboxylic acid. [7] The flux according to any one of [1] to [6], wherein the content of the organic acid is 10% by mass or more with respect to the total mass of the flux. [8] The flux according to any one of [1] to [7], wherein the rosin content is 0 to 1% by mass relative to the total mass of the flux.

[0017] [9] A flux for thermocompression soldering, as described in any one of [1] to [8]. Solder paste containing the flux described in any one of

[10] [1] to [8] and solder powder. A method for manufacturing a joint, comprising the step of obtaining a joint by soldering a component on which solder balls are placed to the soldering surface of a substrate treated with any one of

[11] [1] to [8] by thermocompression bonding. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a flux that remains in the applied area even after preheating at high temperatures for a long period of time, thereby improving bonding reliability, a solder paste containing the flux, and a method for manufacturing a bonded body using the flux. [Brief explanation of the drawing]

[0019] [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]

[0020] 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."

[0021] 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.

[0022] (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 nonionic surfactant, an organic acid, and a solvent.

[0023] <Nonionic surfactant> Nonionic surfactants include compounds (SU0) represented by the following general formula (SU0).

[0024] [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.

[0025] 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.

[0026] 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.

[0027] The cyclic hydrocarbon group may be an aliphatic hydrocarbon group, an aromatic hydrocarbon group, a polycyclic group, or a monocyclic group.

[0028] R a1 , R a2 and R a3 Examples of oxyalkylene groups that may be present include oxyethylene groups, oxypropylene groups, and oxybutylene groups.

[0029] R a1 , R a2 and R a3 In this, the total number of repeating oxyalkylene groups is preferably 20 to 100, and more preferably 25 to 80.

[0030] The compound (SU0) is preferably the compound (SU0-1) represented by the following general formula (su0-1).

[0031] [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).

[0032] 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.

[0033] p11, p12, and p13 are each preferably integers between 6 and 15, more preferably between 8 and 12, and even more preferably 10.

[0034] q11, q12, and q13 are each preferably integers between 2 and 10, more preferably between 3 and 8, and even more preferably 5.

[0035] 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, and more preferably that 25 ≤ n11 + n12 + n13 + m11 + m12 + m13 ≤ 80.

[0036] The compound (SU0) may be one type or two or more types. 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 flux is more likely to remain in the coated area even after prolonged preheating at high temperatures, 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 coated area onto the substrate. If the value is above the lower limit of the aforementioned preferred range, the flux-coated area will be more easily maintained even after prolonged preheating at high temperatures, thereby improving bonding reliability. If the value is below the upper limit of the preferred range mentioned above, even if preheating is performed at a high temperature for a long time, it becomes easier to suppress the flux from wetting and spreading onto the substrate beyond the applied area.

[0037] <<Other Nonionic Surfactants>> The flux according to this embodiment may contain nonionic surfactants other than compound (SU0) (other nonionic surfactants).

[0038] Other nonionic surfactants include, for example, polyoxyalkylene adducts other than compound (SU0). Examples of alkylene oxides derived from polyoxyalkylene adducts other than compound (SU0) include ethylene oxide, propylene oxide, and butylene oxide. Examples of polyoxyalkylene adducts other than compound (SU0) include polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol copolymer, ethylene oxide-resorcinol copolymer, polyoxyalkylene acetylene glycols, polyoxyalkylene alkyl ethers, polyoxyalkylene esters, and polyoxyalkylene alkylamides. Alternatively, other nonionic surfactants include polyoxyalkylene adducts of alcohols other than glycerin. Examples of alcohols other than glycerin include aliphatic alcohols, aromatic alcohols, and polyhydric alcohols.

[0039] Other nonionic surfactants may be one type or two or more types. If the flux contains other nonionic surfactants, the content of other nonionic surfactants in the flux is preferably more than 0% by mass and 60% by mass or less, more preferably more than 0% by mass and 50% by mass or less, and may be 10 to 50% by mass, based on the total mass of the flux.

[0040] The content of nonionic surfactant in the flux is preferably 0.2 to 70% by mass, and more preferably 0.3 to 50% by mass, relative to the total mass of the flux.

[0041] The ratio of compound (SU0) content to nonionic surfactant content in the flux is preferably 0.1 to 100% by mass, and more preferably 0.3 to 100% by mass, expressed as a mass ratio of compound (SU0) / nonionic surfactant. If the ratio of compound (SU0) content to nonionic surfactant content is within the aforementioned preferred range, the flux is more likely to be maintained in the coated area even after prolonged preheating at high temperatures, thereby improving bonding reliability. If the value is above the lower limit of the aforementioned preferred range, the flux-coated area will be more easily maintained even after prolonged preheating at high temperatures, thereby improving bonding reliability.

[0042] <Organic acid> Examples of organic acids include 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.

[0043] 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.

[0044] 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, salicylic acid, picolinic acid, 3-hydroxypicolinic acid, p-anisic acid, m-anisic acid, o-anisic 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, salicylic acid, 3-hydroxypicolinic acid, parahydroxyphenylacetic acid, 2-hydroxybenzoic acid, 4-hydroxybenzoic acid, 2,3-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, and 2,6-dihydroxybenzoic acid. Examples of aromatic dicarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, phenylsuccinic acid, dipicolinic acid, and dibutylaniline diglycolic acid.

[0045] Examples of tricarboxylic acids include citric acid and isocitric acid.

[0046] 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.

[0047] Other examples of carboxylic acids include tris(2-carboxyethyl) isocyanurate and 1,3-cyclohexanedicarboxylic acid.

[0048] 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).

[0049] Examples of organic sulfonic acids include aliphatic sulfonic acids and aromatic sulfonic acids. Examples of aliphatic sulfonic acids include alkanesulfonic acids and alkanolsulfonic acids.

[0050] The organic acid may be one type or two or more types. As for the organic acid, carboxylic acids are preferred, monocarboxylic acids are more preferred, one or more selected from the group consisting of aliphatic monocarboxylic acids, aromatic monocarboxylic acids and hydroxymonocarboxylic acids are even more preferred, hydroxymonocarboxylic acids are particularly preferred, and one or more selected from the group consisting of aliphatic hydroxymonocarboxylic acids and aromatic hydroxymonocarboxylic acids are most preferred.

[0051] The content of organic acids in the flux may be 1 to 40% by mass, 3 to 30% by mass, preferably 10% by mass or more, and more preferably 10 to 30% by mass, relative to the total mass of the flux. If the organic acid content in the flux is within the aforementioned preferred range, the flux will be more easily retained in the applied area even after prolonged preheating at high temperatures, thereby improving bonding reliability. If the value is above the lower limit of the aforementioned preferred range, it becomes easier to suppress the flux from wetting and spreading beyond the coated area onto the substrate, even with high-temperature, long-duration preheating. If the temperature is below the upper limit of the preferred range mentioned above, the flux-coated area will be more easily maintained even after prolonged preheating at high temperatures, making it easier to improve bonding reliability.

[0052] The ratio of compound (SU0) content to organic acid content in the flux is preferably 0.2 to 50%, and more preferably 0.5 to 30%, expressed as compound (SU0) / organic acid. If the ratio of the compound (SU0) content to the organic acid content is within the aforementioned preferred range, the flux will be more easily maintained in the coated area even after preheating at high temperatures for a long time, thereby improving bonding reliability. If the value is above the lower limit of the aforementioned preferred range, even with high-temperature, long-duration preheating, the wettability of the flux to the substrate is enhanced, making it easier for the flux to spread across the substrate. If the temperature is below the upper limit of the preferred range mentioned above, the flux-coated area will be more easily maintained even after prolonged preheating at high temperatures, making it easier to improve bonding reliability.

[0053] <Solvent> Examples of solvents include water, alcohol-based solvents, glycol ether-based solvents, and terpineols.

[0054] 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.

[0055] 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.

[0056] 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).

[0057] The solvent may be one type or two or more types. The solvent content in the flux is preferably 5 to 50% by mass, more preferably 10 to 40% by mass, and even more preferably 10 to 30% by mass, relative to the total mass of the flux.

[0058] <Other ingredients> The flux according to this embodiment may contain, or may not contain, other components in addition to the compound (SUO), organic acid, and solvent, as needed. Other components include the aforementioned nonionic surfactants, surfactants other than organic acids (other surfactants), thixotropic agents, resin components, metal deactivators, silane coupling agents, antioxidants, colorants, etc.

[0059] The flux according to this embodiment may consist of a compound (SU0), an organic acid, a solvent, and optionally one or more other components selected from the group consisting of nonionic surfactants, activators other than organic acids (other activators), thixotropic agents, resin components, metal deactivators, silane coupling agents, antioxidants, and colorants. Each component constituting the group of other components can be arbitrarily selected.

[0060] <<Other Activating Agents>> Other activators include, for example, amines, halogen compounds, and organophosphorus compounds.

[0061] [amine] Examples of amines include amino alcohols, azoles, guanidines, alkylamine compounds, and amine polyoxyalkylene adducts.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] Examples of alkylamine compounds include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, and stearylamine.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] Amines may be used individually or in mixtures of two or more. The flux according to this embodiment preferably contains an amine, and more preferably contains an azole or an amine polyoxyalkylene adduct.

[0070] The content of amino alcohols, azoles, guanidines, or alkylamine compounds in the flux is preferably 2% by mass or more and 20% by mass or less, and more preferably 4% by mass or more and 10% by mass or less, relative to the total mass of the flux.

[0071] The content of amine polyoxyalkylene adducts in the flux is preferably 0% to 80% by mass, and more preferably 3% to 70% by mass, relative to the total mass of the flux.

[0072] The total content of other nonionic surfactants and amine polyoxyalkylene adducts in the flux may be 20% by mass or more and 80% by mass or less, preferably 30% by mass or more, and more preferably 30% by mass or more and 70% by mass or less, based on the total mass of the flux. If the total content of other nonionic surfactants and amine polyoxyalkylene adducts is within the aforementioned preferred range, the flux will be more easily maintained in the coated area even after prolonged preheating at high temperatures, thereby improving bonding reliability. If the value is above the lower limit of the aforementioned preferred range, the flux-coated area will be more easily maintained even after prolonged preheating at high temperatures, thereby improving bonding reliability.

[0073] The ratio of compound (SU0) content to the total content of nonionic surfactant and amine polyoxyalkylene adduct in the flux is preferably 0.1 to 20%, and more preferably 0.2 to 10%, expressed as compound (SU0) / (nonionic surfactant and amine polyoxyalkylene adduct). If the ratio of the compound (SU0) content to the total content of the nonionic surfactant and amine polyoxyalkylene adduct is within the aforementioned preferred range, the flux will be more easily maintained in the coated area even after preheating at high temperatures for a long time, thereby improving bonding reliability. If the value is above the lower limit of the aforementioned preferred range, the flux-coated area will be more easily maintained even after prolonged preheating at high temperatures, thereby improving bonding reliability. If the value is below the upper limit of the preferred range mentioned above, even if preheating is performed at a high temperature for a long time, it becomes easier to suppress the flux from wetting and spreading onto the substrate beyond the applied area.

[0074] [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. Halogen compounds may be used individually or in combination of two or more.

[0075] If the flux contains other activators, the content of the other activators in the flux is preferably 3% to 80% by mass, and more preferably 5% to 70% by mass, based on the total mass (100% by mass) of the flux.

[0076] If the flux contains other activators, the total content of organic acids and other activators in the flux is preferably 20% to 90% by mass, and more preferably 30% to 80% by mass, based on the total mass (100% by mass) of the flux.

[0077] ≪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.

[0078] When the flux contains a thixotropic agent, the thixotropic agent content in the flux is preferably greater than 0% by mass and 1% by mass or less, more preferably greater than 0% by mass and 0.5% by mass or less, even more preferably greater than 0% by mass and 0.3% by mass or less, and particularly preferably greater than 0% by mass and 0.1% by mass or less, based on the total mass (100% by mass) of the flux.

[0079] ≪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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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 (100% by mass). It is preferable that the flux does not contain a resin component.

[0084] 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.

[0085] ≪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. Metal deactivators may be used individually or in combination 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 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, based on the total mass of the flux.

[0086] • Antioxidant Examples of antioxidants include hindered phenol-based antioxidants such as 2,2'-dihydroxy-3,3'-bis(α-methylcyclohexyl)-5,5'-dimethyldiphenylmethane.

[0087] 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.

[0088] • 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 content 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.

[0089] • Colorants Examples of coloring agents include those known to those skilled in the art. The coloring agent may be used individually 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.

[0090] The flux according to this embodiment, as described above, contains a compound (SU0) represented by the general formula (SU0) and an organic acid, making it possible to maintain the flux in the coated area even after preheating at high temperatures for a long period of time. Compound (SU0) has an oxyalkylene group, resulting in low surface tension (high wettability) and poor compatibility with solvents that have high surface tension (low wettability). Compound (SU0) has a large molecular weight, making it resistant to decomposition even at high temperatures. The organic acid acts antagonistically with compound (SU0) to control the wettability within an appropriate range. Due to these synergistic effects, the flux according to this embodiment can maintain its flux-coated area even after prolonged preheating at high temperatures.

[0091] Alternatively, from another perspective, the flux may also be in the following embodiments. <1> A flux containing a nonionic surfactant, an activator, and a solvent, wherein the nonionic surfactant comprises a compound (SU0) represented by the following general formula (SU0), and the activator comprises an organic acid and an amine.

[0092] [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.

[0093] <2> The aforementioned compound (SU0) is compound (SU0-1) represented by the following general formula (su0-1): <1> The flux described above.

[0094] [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).

[0095] <3> The content of the aforementioned compound (SU0) is 0.2 to 4% by mass relative to the total mass of the flux. <1> or <2> The flux described above.

[0096] <4> The amine contains one or more selected from the group consisting of amine polyoxyalkylene adducts and azoles. <1> ~ <3> The flux described in any one of the following lists.

[0097] <5> The flux contains the amine polyoxyalkylene adduct, and the total content of the nonionic surfactant other than compound (SU0) and the amine polyoxyalkylene adduct is 30% by mass or more relative to the total mass of the flux. <1> ~ <4> The flux described in any one of the following lists.

[0098] <6> The aforementioned organic acid includes a monocarboxylic acid. <1> ~ <5> The flux described in any one of the following lists.

[0099] <7> The content of the aforementioned organic acid is 10% by mass or more relative to the total mass of the flux. <1> ~ <6> The flux described in any one of the following lists.

[0100] <8> The rosin content is 0-1% by mass relative to the total mass of the flux. <1> ~ <7> The flux described in any one of the following lists.

[0101] (Solder paste) The solder paste of this embodiment contains solder alloy powder and the flux described above.

[0102] 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.

[0103] 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.

[0104] According to the solder paste of the embodiment described above, by containing the flux according to the embodiment, the solder paste can be maintained in the applied area even after preheating at high temperatures for a long time, thereby improving bonding reliability.

[0105] (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.

[0106] <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.

[0107] Examples of the substrate 10 include printed circuit boards. The flux according to the above embodiment is preferably used as the flux 12. 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. 2Preferably, it is 10-150 mL / m² 2 It is more preferable that the concentration be 15-120 mL / m². 2 It is particularly preferable that this be the case.

[0108] <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.

[0109] <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.

[0110] 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.

[0111] In the thermocompression bonding process, the temperature at which the component 20 is heated may be, for example, 250 to 320°C, or 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.

[0112] According to the method for manufacturing the bonded body of this embodiment described above, by using the flux 12 according to the embodiment, it is possible to improve the bonding reliability between the substrate 10 and the component 20. [Examples]

[0113] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0114] <Preparation of flux> (Examples 1-8, Comparative Examples 1-5) Fluxes for the examples and comparative examples were prepared with the compositions shown in Table 1. The components of the raw materials used are shown below. The content in Table 1 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.

[0115] Nonionic surfactants As specific nonionic surfactants, compounds (SU0-1-1) to (SU0-1-3) represented by the following chemical formula (SU0-1-0) were used. Compound (SU0-1-1) is a compound in which a+b+c=25 in the following chemical formula (SU0-1-0). Compound (SUO-1-2) is a compound in which a+b+c=60 in the following chemical formula (SUO-1-0). Compound (SUO-1-3) is a compound in which a+b+c=80 in the following chemical formula (SUO-1-0).

[0116] [ka]

[0117] As an alternative nonionic surfactant, a resorcinol ethylene oxide adduct was used.

[0118] Comparative compound As comparative compounds, we used compounds (SUC-1) to (SUC-5) represented by the following chemical formulas (suc-1) to (suc-5).

[0119] Compound (SUC-1) Polyethylene glycol lauryl ether

[0120] [ka]

[0121] Compound (SUC-2) Polyethylene glycol (19) lauryl ether

[0122] [ka]

[0123] Compound (SUC-3) Polyethylene glycol (5) oleyl ether

[0124] [ka]

[0125] Compound (SUC-4) Polyethylene glycol (5) alkyl (sec-C11-15) ether

[0126] [ka] [In the formula, R c1 and R c2 Each of these is an alkyl group having 1 or more carbon atoms, and R c1 and R c2 The total number of carbon atoms in this compound is between 11 and 15.

[0127] Compound (SUC-5) Polyethylene glycol (9) alkyl (sec-C11-15) ether

[0128] [ka] [In the formula, R c3 and R c4 Each of these is an alkyl group having 1 or more carbon atoms, and R c3 and R c4 The total number of carbon atoms in this compound is between 11 and 15.

[0129] Organic acids: Salicylic acid, 2,2-bishydroxymethylpropionic acid

[0130] Amine: 2-Ethylimidazole

[0131] 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.

[0132] solvent: Dipropylene glycol monomethyl ether, hexylene glycol

[0133] The flux retention was evaluated according to the evaluation method described below. The evaluation results are shown in Table 1.

[0134] <Evaluation of flux retention> (1) Evaluation method Each example of flux was applied to the flux-coated area of ​​a glass epoxy substrate (size 105mm x 105mm, 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.

[0135] (2) Judgment criteria In the area where flux A was applied, there were no areas where the flux was not maintained and 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.

[0136] [Table 1]

[0137] As shown in Table 1, Examples 1-8, which contained compound (SU0), showed superior flux retention compared to Comparative Examples 1-5, which did not contain compound (SU0). [Industrial applicability]

[0138] 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]

[0139] 10 PCBs, 11 pads, 12 flux, 20 components, 21 solder balls, 30 bonding heads

Claims

1. It contains a nonionic surfactant, an organic acid, and a solvent. The nonionic surfactant comprises a compound (SU0) represented by the following general formula (SU0), The content of the compound (SU0) is 0.2 to 4% by mass relative to the total mass of the flux. The content of the aforementioned organic acid is 1 to 40% by mass relative to the total mass of the flux. A flux in which the ratio of the compound (SU0) content to the organic acid content is 0.5 to 50%, expressed as compound (SU0) / organic acid. 【Chemistry 1】 [wherein, R ａ１ , R ａ２ and R ａ３ are each independently an organic group. However, at least one 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.]

2. The flux according to claim 1, wherein the compound (SU0) is compound (SU0-1) represented by the following general formula (su0-1). 【Chemistry 2】 [In the formula, R ａ１１ , R ａ１２ , R ａ１３ , R ｂ１１ , R ｂ１２ and R ｂ１３ Each of these is independently of -C ２ H ４ - or -CH ２ -CH(CH ３ This represents n11, n12, n13, m11, m12, and m13 being integers greater than or equal to 0. 15 ≤ n11 + n12 + n13 + m11 + m12 + m13 ≤ 120. p11, p12, p13, q11, q12, and q13 are each independently integers between 1 and 18 (inclusive).

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

4. Furthermore, the nonionic surfactant other than the compound (SU0) is included, The flux according to claim 3, wherein the total content of the nonionic surfactant other than the compound (SU0) and the amine polyoxyalkylene adduct is 20% by mass or more and 80% by mass or less based on the total mass of the flux.

5. The flux according to claim 1, wherein the organic acid includes a monocarboxylic acid.

6. The flux according to claim 1, wherein the content of the organic acid is 10% by mass or more relative to the total mass of the flux.

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

8. A flux according to any one of claims 1 to 7, for use in thermocompression soldering.

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

10. A method for manufacturing a joint, comprising the step of obtaining a joint by soldering a component on which solder balls are placed to the soldering surface of a substrate treated with the flux described in any one of claims 1 to 7 by thermocompression bonding.

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