Flux and solder paste using the same

Abstract

To provide flux which enables improvement of storage performance of solder paste while effectively suppressing scattering of the flux during reflowing.SOLUTION: This flux includes a thixotropic agent. The thixotropic agent includes an alkylene oxide copolymer (A) having an allyl group and / or a phenyl group in a side chain.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a flux and a solder paste using the same.

Background Art

[0002] Conventionally, in electronic devices such as mounting electronic components on a printed circuit board, fixing and electrical connection of electronic components are generally performed by soldering. In soldering, a flux, which is an auxiliary agent that facilitates the adhesion of solder to a printed circuit board and electronic components, is used, and various developments have been made on fluxes for soldering. On the other hand, such fluxes for soldering are in a high-temperature state during soldering, and thus the solvent components contained therein may boil suddenly and the molten flux may scatter. Therefore, as a technique for suppressing the scattering of such fluxes, for example, the technique described in Patent Document 1 is known. Patent Document 1 discloses a flux containing a base resin, a solvent, an activator, a thixotropic agent, and a polyalkylene oxide polymer having a weight average molecular weight of 2,000 Mw or more and 1,000,000 Mw or less (Claim 1 of Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, as a result of the inventor's study, it has been found that even the flux described in Patent Document 1 above has room for improvement in terms of suppressing the scattering of the flux during reflow. Further, when the flux is applied to the solder paste, the flux component may ooze out during the storage and preservation of the solder paste, and the flux and the solder powder may separate. Therefore, it is required to suppress the separation between the flux and the solder powder and improve the storage stability of the solder paste.

Means for Solving the Problems

[0005] As a result of further study by the inventor, it has been surprisingly found that by using an alkylene oxide copolymer having an allyl group and / or a phenyl group in the side chain in the flux, it is possible to more effectively suppress the scattering of the flux during reflow and improve the storage stability of the solder paste.

[0006] According to the present invention, a flux containing a thixotropic agent, wherein the thixotropic agent contains an alkylene oxide copolymer (A) having an allyl group and / or a phenyl group in the side chain, is provided.

[0007] Also according to the present invention, a solder paste containing the above flux and metal powder is provided.

Effects of the Invention

[0008] According to the present invention, there are provided a flux capable of more effectively suppressing the scattering of the flux during reflow and improving the storage stability of the solder paste, and a solder paste using the same.

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail. In this specification, the term "substantially" means including the range considering manufacturing tolerances, assembly variations, etc., unless otherwise explicitly stated. In this specification, the notation "a to b" in the description of a numerical range means a or more and b or less, unless otherwise specified. For example, "1 to 5 mass%" means "1 mass% or more and 5 mass% or less".

[0010] <Flux> The flux of this embodiment is a flux containing a thixotropic agent, and the thixotropic agent contains an alkylene oxide copolymer (A) having an allyl group and / or a phenyl group in the side chain. Thereby, while more effectively suppressing the scattering of the flux during reflow, the storage stability of the solder paste can be improved.

[0011] Hereinafter, each component contained in the flux will be described.

[0012] [Thixotropic agent] The thixotropic agent is used to impart thixotropy to the flux and the solder paste. The thixotropic agent of this embodiment contains at least an alkylene oxide copolymer (A) having an allyl group and / or a phenyl group in the side chain. That is, since the alkylene oxide copolymer (A) has a bulky hydrophobic group such as an allyl group and / or a phenyl group in the side chain, a surface-active effect is obtained, whereby the dispersibility of the solder powder is improved, and it is easy to suppress the separation between the flux component and the solder powder. Also, it is considered that by improving the stringiness, the scattering of small lumps of the flux component can be suppressed. In addition, by using polyalkylene oxide as the main skeleton, a good viscosity is obtained, and an appropriate viscosity is maintained even at high temperatures due to reflow, making it easy to suppress the scattering of the flux component. Also, during the storage of the flux, sedimentation of the solder powder due to an increase in viscosity and thixotropy can be suppressed, and separation from the flux component is less likely to occur. In this embodiment, there is no problem with the separation of the solder powder and the flux component during reflow.

[0013] (Alkylene Oxide Copolymer (A)) The alkylene oxide copolymer (A) is preferably a copolymer of a polyalkylene oxide and a glycidyl ether having an allyl group and / or a phenyl group in the side chain. The content of the allyl group and / or phenyl group in the side chain of the alkylene oxide copolymer (A) is preferably 1 to 12% by mass.

[0014] Examples of the polyalkylene oxide include ethylene oxide, propylene oxide, 1,4-butylene oxide (tetrahydrofuran), etc. Among them, ethylene oxide and propylene oxide are preferable, and those having both ethylene oxide and propylene oxide are more preferable.

[0015] Specific examples of the alkylene oxide copolymer (A) include, for example, one or two selected from a ternary copolymer (a1) of ethylene oxide, propylene oxide, and allyl glycidyl ether, and a ternary copolymer (a2) of ethylene oxide, propylene oxide, and phenyl glycidyl ether.

[0016] When the copolymerization ratio of ethylene oxide, propylene oxide, and allyl glycidyl ether in the ternary copolymer (a1) of ethylene oxide, propylene oxide, and allyl glycidyl ether is n, m, l (mol%), it is preferably n:m:l = 96 to 93:1 to 6:3 to 1.

[0017] When the copolymerization ratio of ethylene oxide, propylene oxide, and phenyl glycidyl ether in the ternary copolymer (a2) of ethylene oxide, propylene oxide, and phenyl glycidyl ether is x, y, z (mol%), it is preferably x:y:z = 98 to 97:1:1 to 2.

[0018] Also, the alkylene oxide copolymer (A) is a random copolymer containing ethylene oxide, propylene oxide, phenyl or allyl glycidyl ether as repeating units.

[0019] The weight average molecular weight of the alkylene oxide copolymer (A) is preferably from 50,000 to 800,000, more preferably from 60,000 to 600,000, still more preferably from 70,000 to 500,000, even more preferably from 80,000 to 200,000, and particularly preferably from 90,000 to 150,000. Thereby, the difference in specific gravity between the solder powder and the flux component can be reduced, and the storage stability can be improved.

[0020] Also, the aqueous solution viscosity (concentration 10 mass%) of the alkylene oxide copolymer (A) is preferably from 50 to 3000 mPa·s, and more preferably from 100 to 2000 mPa·s.

[0021] The content of the alkylene oxide copolymer (A) is preferably 50 mass% or more, more preferably 60 mass% or more, still more preferably 80 mass% or more, even more preferably 90 mass% or more, particularly preferably 98 mass% or more, and may be 100 mass% based on the total amount of the thixotropic agent.

[0022] Also, the thixotropic agent of this embodiment may further contain a thixotropic agent other than the above alkylene oxide copolymer (A). The other thixotropic agents are not particularly limited, and known ones can be used. For example, amide compounds, ester compounds, sorbitol-based thixotropic agents, carnauba wax, and wax-based thixotropic agents such as beeswax can be mentioned.

[0023] Examples of the amide compound as the thixotropic agent described above include monoamide, bisamide, and polyamide. More specifically, for example, such amide compounds include lauric amide, palmitic amide, stearic amide, behenic amide, hydroxystearic amide, saturated fatty acid amide, oleic amide, erucic amide, unsaturated fatty acid amide, p-toluamide, p-toluenemethane amide, aromatic amide, hexamethylene hydroxystearic amide, substituted amide, methylol stearic amide, methylol amide, fatty acid ester amide, etc. of monoamide; methylene bisstearic amide, ethylene bislauric amide, ethylene bishydroxy fatty acid (fatty acid having 6 to 24 carbon atoms) amide, ethylene bishydroxystearic amide, saturated fatty acid bisamide, methylene bisoleic amide, unsaturated fatty acid bisamide, m-xylylene bisstearic amide, aromatic bisamide, etc. of bisamide; saturated fatty acid polyamide, unsaturated fatty acid polyamide, aromatic polyamide, 1,2,3-propanetricarboxylic acid tris(2-methylcyclohexylamide), cyclic amide oligomer, acyclic amide oligomer, etc. of polyamide.

[0024] Examples of the ester compound as the thixotropic agent described above include castor hardened oil and the like.

[0025] Examples of the sorbitol-based thixotropic agent described above include dibenzylidene sorbitol, bis(4-methylbenzylidene) sorbitol, (D-) sorbitol, monobenzylidene(-D-) sorbitol, mono(4-methylbenzylidene)-(D-) sorbitol, etc.

[0026] The content of the thixotropic agent in this embodiment is preferably 0.1 to 20% by mass, more preferably 2 to 15% by mass, and even more preferably 8 to 12% by mass with respect to the total weight of the flux. By setting the content of the thixotropic agent to be below the above upper limit value, it becomes easier to suppress scattering. On the other hand, by setting the content of the thixotropic agent to be above the above lower limit value, the balance between storage stability and scattering suppression can be improved.

[0027] The weight average molecular weight of the thixotropic agent of this embodiment is preferably from 50,000 to 800,000, more preferably from 60,000 to 600,000, still more preferably from 70,000 to 500,000, even more preferably from 80,000 to 200,000, and particularly preferably from 90,000 to 150,000. Further, the flux of this embodiment may contain a plurality of types of thixotropic agents having different weight average molecular weights. As a method for measuring the weight average molecular weight, a method of converting the measurement result of gel permeation chromatography (GPC) using a calibration curve of standard polyethylene glycol is generally known. For example, it can be measured under the following conditions. Measuring device: 1260 Infinity manufactured by Agilent Columns used: TSKguardcolumn SWXL (guard column) manufactured by Tosoh, TSKgel G5000PWXL-CP manufactured by Tosoh, TSKgel G3000PWXL-CP manufactured by Tosoh Mobile phase: 0.1 M aqueous sodium nitrate solution Standard substance: Polyethylene glycol Detector: RI detector, Pol(+) Injection volume: 20 μl Calibration curve: Based on polyethylene glycol

[0028] [Activator] The flux of this embodiment preferably contains an activator. An activator has the property of removing metal oxides and can enhance the solder wettability during the solder joining process. That is, generally, for the solder joining process, it is known to be performed in a reducing gas atmosphere such as formic acid gas, in an inert gas atmosphere containing substantially no reducing gas such as nitrogen gas or argon gas or in a reduced pressure atmosphere, or in an atmospheric pressure environment. Therefore, by including an activator in the flux, it becomes possible to use it in a solder joining process in an inert gas atmosphere or a reduced pressure atmosphere containing substantially no reducing gas.

[0029] As the activator, one or more selected from organic acids, amines, halogen-based activators, and phosphorus-based activators can be mentioned. Although the detailed mechanism is not clear, it is considered that these activators can remove the metal oxide film on the surface of the solder and the metal to be soldered by forming salts or chelates with metal oxides.

[0030] Examples of organic acids include monocarboxylic acids, dicarboxylic acids, anhydrides of dicarboxylic acids, oxyacids, etc. These may be used alone or in combination of two or more. Among these, polyvalent organic acids having two or more of at least one of a hydroxy group and a carboxy group in the molecule may also be used.

[0031] As an example of specific examples of organic acids, for example, glutaric acid, adipic acid, azelaic acid, eicosanedioic acid, citric acid, glycolic acid, succinic acid, salicylic acid, diglycolic acid, dipicolinic acid, dibutylanilinediglycolic acid, suberic acid, sebacic acid, thioglycolic acid, terephthalic acid, dodecanedioic acid, parahydroxyphenylacetic acid, picolinic acid, phenylsuccinic acid, phthalic acid, fumaric acid, maleic acid, malonic acid, lauric acid, benzoic acid, tartaric acid, tris(2-carboxyethyl) isocyanurate, glycine, 1,3-cyclohexanedicarboxylic acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butanoic acid, 2,3-dihydroxybenzoic acid, 2,4-diethylglutaric acid, 2-quinolinecarboxylic acid, 3-hydroxybenzoic acid, malic acid, p-anisic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, and linolenic acid, etc. can be mentioned.

[0032] Among these, from the viewpoint of low residue property, the organic acid may contain an organic acid having 11 or less carbon atoms. Examples of organic acids having 11 or fewer carbon atoms include glycolic acid (2 carbon atoms), thioglycolic acid (2 carbon atoms), glycine (2 carbon atoms), malonic acid (3 carbon atoms), fumaric acid (4 carbon atoms), maleic acid (4 carbon atoms), succinic acid (4 carbon atoms), diglycolic acid (4 carbon atoms), tartaric acid (4 carbon atoms), malic acid (4 carbon atoms), glutaric acid (5 carbon atoms), 2,2-bis(hydroxymethyl)propionic acid (5 carbon atoms), adipic acid (6 carbon atoms), citric acid (6 carbon atoms), picolinic acid (6 carbon atoms), benzoic acid (7 carbon atoms), 2,2-bis(hydroxymethyl)butanoic acid (6 carbon atoms), salicylic acid (7 carbon atoms), dipicolinic acid (7 carbon atoms), 2,3-dihydroxybenzoic acid (7 carbon atoms), 3-hydroxybenzoic acid (7 carbon atoms), suberic acid (8 carbon atoms), phthalic acid (8 carbon atoms), isophthalic acid (8 carbon atoms), terephthalic acid (8 carbon atoms), parahydroxyphenylacetic acid (8 carbon atoms), 1,3-cyclohexanedicarboxylic acid (8 carbon atoms), p-anisic acid (8 carbon atoms), azelaic acid (9 carbon atoms), 2,4-diethylglutaric acid (9 carbon atoms), sebacic acid (10 carbon atoms), phenylsuccinic acid (10 carbon atoms), 2-quinolinecarboxylic acid (10 carbon atoms), 4-tert-butylbenzoic acid (11 carbon atoms), and the like.

[0033] Examples of organic acids also include dimer acid, trimer acid, hydrogenated dimer acid which is a hydrogenated product of dimer acid, and hydrogenated trimer acid which is a hydrogenated product of trimer acid.

[0034] The content of the organic acid in the flux may be, for example, 0 to 15% by mass, or may be 1 to 10% by mass.

[0035] Examples of amines include monoethanolamine, diphenylguanidine, ethylamine, triethylamine, ethylenediamine, triethylenetetramine, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium 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 isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazoline, 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, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol], 6-(2-benzotriazolyl)-4-tert-octyl-6'-tert-butyl-4'-methyl-2,2'-methylenebisphenol, 1,2,3-benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, carboxybenzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, 2,2'-[[(methyl-1H-benzotriazol-1-yl)methyl]imino]bisethanol, 1-(1',2'-dicarboxyethyl)benzotriazole, 1-(2,3-dicarboxypropyl)benzotriazole, 1-[(2-ethylhexylamino)methyl]benzotriazole, 2,6-bis[(1H-benzotriazol-1-yl)methyl]-4-methylphenol, 5-methylbenzotriazole, and 5-phenyltetrazole, etc. can be mentioned.,

[0036] The content of amines in the flux may be, for example, 0 to 15% by mass, or may be 0.5 to 5% by mass.,

[0037] Examples of the halogen-based activator include organic halogen compounds or amine hydrohalide salts, etc.,

[0038] Examples of the organic halogen compound include trans-2,3-dibromo-1,4-butanediol, triallyl isocyanurate hexabromide, 1-bromo-2-butanol, 1-bromo-2-propanol, 3-bromo-1-propanol, 3-bromo-1,2-propanediol, 1,4-dibromo-2-butanol, 1,3-dibromo-2-propanol, 2,3-dibromo-1-propanol, 2,3-dibromo-1,4-butanediol, 2,3-dibromo-2-butene-1,4-diol, and the like. Examples of other organic halogen compounds include chloroalkanes, which are organic chlorine compounds, chlorinated fatty acid esters, het acids, het acid anhydrides, and the like. Further examples include fluorine-based surfactants, surfactants having a perfluoroalkyl group, and polytetrafluoroethylene, which are organic fluorine compounds.

[0039] Examples of the amine hydrohalide salts include salts formed by combining hydrohalic acids such as hydroiodic acid (HI), hydrobromic acid (HBr), hydrochloric acid (HCl), and hydrofluoric acid (HF) with amine compounds such as aniline, diphenylguanidine, diethylamine, and isopropylamine. Further, salts formed by combining tetrafluoroboric acid (HBF4) with amine compounds can also be used as equivalents of amine hydrohalide salts.

[0040] The content of the halogen-based activator in the flux may be, for example, 0 to 10% by mass, or may be 0.5 to 5% by mass. The content of the organic halogen compound in the flux may be, for example, 0 to 5% by mass. The content of the amine hydrohalide salt in the flux may be, for example, 0 to 1% by mass.

[0041] Examples of the phosphorus-based activator include phosphonic acid esters, phenyl-substituted phosphinic acid phosphonic acids, phosphate esters, and the like.

[0042] Examples of the phosphonic acid ester include 2-ethylhexyl (2-ethylhexyl) phosphonate, n-octyl (n-octyl) phosphonate, n-decyl (n-decyl) phosphonate, and n-butyl (n-butyl) phosphonate. Examples of the phenyl-substituted phosphinic acid include phenylphosphinic acid and diphenylphosphinic acid.

[0043] The content of the phosphorus-based activator in the flux may be, for example, 0 to 10% by mass, or may be 1 to 5% by mass.

[0044] The content of the activator may be 0 to 30% by mass, or may be 1 to 20% by mass, or may be 5 to 15% by mass with respect to the total amount of the flux.

[0045] [Solvent] The flux of this embodiment contains a solvent. The solvent is not particularly limited, and examples thereof include solid solvents and liquid solvents. These may be used alone or in combination of two or more.

[0046] The solid solvent may be a solvent that is solid at 25°C, and the lower limit of the melting point may be, for example, 30°C or higher, 40°C or higher, or 50°C or higher. The upper limit of the melting point may be, for example, 280°C or lower.

[0047] Examples of the solid solvent include alcohol-based solid solvents and phenol-based solid solvents. The above alcohol-based solid solvent may be a solid solvent having one or more hydroxy groups in the molecule, and a polyhydric alcohol-based solid solvent having two or more hydroxy groups is preferred. Specific examples of the polyhydric alcohol-based solid solvent include pentaerythritol, trimethylolpropane, 2,5-dimethyl-2,5-hexanediol, neopentyl glycol, and the like. The above-mentioned phenolic solid solvent may be a solid solvent having one or more phenolic groups in the molecule, and one or more hydroxy groups may be bonded to the benzene ring of the phenolic group.

[0048] The content of the solid solvent in the flux may be, for example, 0 to 40% by mass, or 1 to 30% by mass.

[0049] The liquid solvent is a solvent that is liquid at 25°C, and alcohol solvents, glycol ether solvents, terpineols, hydrocarbons, esters, water, etc. are used. These may be used alone or in combination of two or more. Among these, at least one of an alcohol solvent and a glycol ether solvent may be used as the liquid solvent.

[0050] Examples of the above-mentioned alcohol solvents include isopropyl alcohol, 1,2-butanediol, isobornyl cyclohexanol, 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, 1,1,1-tris(hydroxymethyl)ethane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 2,2'-oxybis(methylene)bis(2-ethyl-1,3-propanediol), 2,2-bis(hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, bis[2,2,2-tris(hydroxymethyl)ethyl]ether, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, erythritol, threitol, guaiacol glycerol ether, 3,6-dimethyl-4-octyne-3,6-diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, and the like.

[0051] Examples of the glycol ether solvent include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, 2-methylpentane-2,4-diol, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol monomethyl ether, and the like.

[0052] The content of the liquid solvent in the flux may be, for example, 0 to 50% by mass or 1 to 45% by mass.

[0053] [Base resin] The flux may contain a base resin. Examples of the base resin include rosin resins, (meth)acrylic resins, urethane resins, polyester resins, phenoxy resins, vinyl ether resins, terpene resins, modified terpene resins (e.g., aromatic modified terpene resins, hydrogenated terpene resins, hydrogenated aromatic modified terpene resins, etc.), terpene phenol resins, modified terpene phenol resins (e.g., hydrogenated terpene phenol resins, etc.), styrene resins, modified styrene resins (e.g., styrene acrylic resins, styrene maleic resins, etc.), xylene resins, modified xylene resins (e.g., phenol modified xylene resins, alkylphenol modified xylene resins, phenol modified resol type xylene resins, polyol modified xylene resins, polyoxyethylene added xylene resins, etc.). These may be used alone or in combination of two or more. In the present specification, the term "(meth)acrylic resin" refers to a concept including methacrylic resins and acrylic resins.

[0054] Among these, the base resin preferably contains a rosin resin. Examples of rosin resins include raw rosins such as gum rosin, wood rosin, and tall oil rosin, and derivatives obtained from raw rosins. Examples of derivatives include purified rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, and α,β-unsaturated carboxylic acid-modified products (acrylated rosin), maleated rosin, fumarated rosin, etc., as well as purified products, hydrides, and disproportionated products of polymerized rosin, and purified products, hydrides, disproportionated products, etc. of α,β-unsaturated carboxylic acid-modified products. These rosin resins may be used alone or in combination of two or more.

[0055] The content of the base resin in the flux may be, for example, 10 to 70% by mass, or may be 20 to 50% by mass. The content of the base resin is appropriately adjusted according to other components in the flux.

[0056] [Additives] The flux may contain additives that are usually added to the flux, as long as the effects of the present invention are not impaired. Examples of additives include antioxidants such as hindered phenol-based antioxidants and phosphorus-based antioxidants, rust preventives, defoaming agents, matting agents, surfactants, and colorants. These may be used alone or in combination of two or more.

[0057] [Uses] The flux of the present embodiment can be used, for example, as a solder paste by mixing with metal powder, or as a flux for ball attachment or chip attachment.

[0058] [Solder Paste] The solder paste of the present embodiment contains the above flux and metal powder.

[0059] The metal powder may be composed of Sn alone, or solder powder such as Sn-Ag-based, Sn-Cu-based, Sn-Ag-Cu-based, Sn-Bi-based, Sn-In-based, etc., or alloys thereof added with Pb, Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc.

[0060] The solder alloy preferably has an alloy composition consisting of at least one of As: 25 to 300 ppm by weight, and Sb: more than 0 ppm by weight and 3000 ppm by weight or less, Bi: more than 0 ppm by weight and 10000 ppm by weight or less, and Pb: more than 0 ppm by weight and 5100 ppm by weight or less, with the balance being Sn. The solder alloy may further contain at least one of Ag: 0 to 4% by mass and Cu: 0 to 0.9% by mass.

[0061] There is no limitation on the contents of the metal powder and the flux in the solder paste. For example, the metal powder can be 5 to 95% by mass and the flux can be 5 to 95% by mass.

[0062] There is no limitation on the manufacturing method of the flux and the solder paste, and they can be manufactured by mixing the raw materials simultaneously or sequentially by any method. For example, in the manufacturing method of the flux, it is only necessary that all the components of the flux are finally mixed. Other components can be sequentially mixed into the solvent, or the mixture of other components can be added to the solvent, or the solvent and all other components can be mixed simultaneously. Also, in the manufacturing method of the solder paste, it is not necessarily required to prepare the flux in advance and mix it with the metal powder. As long as all the components of the flux, the metal powder, and the additives added to the solder paste as required are finally mixed, the order of mixing is not limited. For example, after mixing a part of the components of the flux with the metal powder, the remaining components of the flux can be added.

[0063] As an example, the flux and the solder paste of the present embodiment can be used in a method for manufacturing a semiconductor device. The method for manufacturing a semiconductor device may include a step of applying the flux or the solder paste to an electrode, placing solder balls on the electrode, and then performing a heat treatment on a substrate such as a lead frame or a printed wiring board and a semiconductor element to join them through the melted solder balls. The heat treatment may be performed in a nitrogen atmosphere or a reduced-pressure atmosphere, and may be performed under conditions where the heating rate is, for example, 3 °C / sec or more. The method for manufacturing a semiconductor device may be configured not to include a step of cleaning the flux or solder paste after the bonding step.

[0064] As described above, the embodiments of the present invention have been described, but these are examples of the present invention, and various configurations other than the above can be adopted. Further, the present invention is not limited to the above-described embodiments, and modifications, improvements, etc. within the scope capable of achieving the object of the present invention are included in the present invention.

Example

[0065] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the descriptions of these examples at all.

[0066] 1. Preparation of Flux A flux was obtained by mixing the following raw materials in the mixing ratios shown in Tables 1 and 2 by a known method. (Base Resin) · Base Resin 1: Acrylic Acid-Modified Hydrogenated Rosin · Base Resin 2: Hydrogenated Rosin · Base Resin 3: Rosin Ester · Base Resin 4: Polymerized Rosin (Solvent) · Solvent 1: Hexyl Diglycol (Diethylene Glycol Monohexyl Ether) · Solvent 2: Hexylene Glycol (2-Methylpentane-2,4-diol) (Activator) · Organic Acid 1: Glutaric Acid · Organic Acid 2: Adipic Acid · Amines: 2-Ethylimidazole · Halogen-Based Activator: 2,3-Dibromo-1,4-butanediol (Thixotropic Agent) · Thixotropic Agent 1: Hydrogenated Castor Oil · Thixotropic Agent 2: Polyamide-Based Thixotropic Agent · Thixotropic agent 3: Polyethylene oxide ("Alcox L-11" manufactured by Meisei Chemical Industry Co., Ltd., weight average molecular weight 110,000 (catalog value)) · Alkylene oxide copolymer (A) 1: Thixotropic agent ethylene oxide · propylene oxide · allyl glycidyl ether random copolymer ("Alcox CP-A1H" manufactured by Meiwafosis Co., Ltd., weight average molecular weight 100,000 (catalog value)) · Alkylene oxide copolymer (A) 2: Ethylene oxide · propylene oxide · phenyl glycidyl ether random copolymer ("Alcox CP-B1" manufactured by Meiwafosis Co., Ltd., weight average molecular weight 100,000 (catalog value))

[0067] 2. Preparation of solder paste The obtained flux and metal powder were mixed at a ratio of 13% by mass of flux: 87% by mass of metal powder to obtain a solder paste. As the metal powder, a Sn-Ag-Cu-based solder alloy in which Ag is 3.0% by mass, Cu is 0.5% by mass, and the balance is Sn (average particle size of the metal powder is φ20 μm) was used. Note that the particle size of the metal powder was classified as symbol 6 in Table 2 (Classification of Powder Sizes) of JIS Z 3284-1:2014.

[0068] 3. Evaluation Using the obtained solder paste, the following evaluation items were evaluated.

[0069] <Spattering property> Each obtained solder paste was printed on a FR-4 (Flame Retardant Type4) substrate using a metal mask (mask thickness 0.15 mm, aperture size 1.6 mm × 1.6 m). Next, 30 chip capacitors with a size of 3.2 mm × 1.6 mm were mounted on the printed part and mounted in a reflow furnace. The reflow temperature profile was as follows (i) to (iv). (i) Heating up to 150 °C at 2 °C / second (ii) Heating up to 150 to 180 °C in 80 seconds (iii) Heating up to 180 to 240 °C at 2 °C / second (iv) Hold at 220 °C or higher for 40 seconds The number of flux residues scattered outside (around) the mounting positions of 30 chip capacitors was measured respectively, the measured values for 30 locations were totaled, and the evaluation was made according to the following criteria. Note that the number of flux residues was counted as one lump regardless of its size. · Criteria ○: 0 to 5 pieces △: 6 to 15 pieces ×: 16 pieces or more

[0070] <Storage stability (shelf life)>[[ / END]] 100 g of each solder paste was put into a paste container (cylindrical with an inner diameter of 58 mm), and stirred with a softener (Shin Key ARV-930TWIN) at a rotation speed of 200 rpm for 2 minutes. Subsequently, the lid was closed and sealed, and it was left at room temperature (25 ± 3 °C, 60% RH or less) in that state. After that, the lid was opened every 24 hours, the paste container was tilted, and it was visually confirmed whether the flux component flowed out (or oozed out) from the solder paste. The time when it flowed out was evaluated according to the following criteria. · Criteria ○: It did not flow out even after 168 hours. △: It flowed out between 72 hours and less than 168 hours. ×: It flowed out in less than 72 hours.

[0071] [Table 1][[ / END]]

[0072] [Table 2][[ / END]]

Claims

1. A flux containing a thixotropic agent, wherein the thixotropic agent contains an alkylene oxide copolymer (A) having an allyl group and / or a phenyl group in the side chain. The flux

2. The flux according to claim 1, wherein the weight average molecular weight of the thixotropic agent is 50,000 to 800,000. The flux

3. The flux according to claim 1 or 2, wherein the content of the thixotropic agent is 0.1 to 20% by mass based on the total weight of the flux. The flux

4. The flux according to any one of claims 1 to 3, wherein the alkylene oxide copolymer (A) is a copolymer of a polyalkylene oxide and a glycidyl ether having an allyl group and / or a phenyl group in the side chain. The flux

5. The flux according to any one of claims 1 to 4, wherein the alkylene oxide copolymer (A) is one or two selected from an ethylene oxide / propylene oxide / allyl glycidyl ether random copolymer and an ethylene oxide / propylene oxide / phenyl glycidyl ether random copolymer. The flux

6. The flux according to any one of claims 1 to 5, wherein the alkylene oxide copolymer (A) is a random copolymer. The flux

7. The flux according to any one of claims 1 to 6, further comprising rosin. The flux

8. The flux according to any one of claims 1 to 7, further comprising one or more activators selected from organic acids, amines, halogen-based activators, and phosphorus-based activators. The flux

9. The flux according to claim 8, wherein the activator contains an organic acid having 11 or less carbon atoms. The flux

10. A solder paste containing the flux according to any one of claims 1 to 9 and metal powder

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