Soldering flux, soldering paste and preparation method of joint body

Abstract

The flux of the present invention contains a first solvent and a thixotropic agent. The first solvent has a viscosity of 10 Pa.s or more at 30 DEG C, or is a solid at 30 DEG C, has a boiling point of 200 DEG C or more, and has a weight loss rate of less than 96 mass% when heated to 230 DEG C. The thixotropic agent contains one or more polyamides selected from the group consisting of condensates of aliphatic carboxylic acids and amines, and condensates of aliphatic carboxylic acids, hydroxyl group-containing aliphatic carboxylic acids, and amines. The content of the first solvent is 30% by mass or more relative to the total mass of the flux. The content of the polyamide is more than 2% by mass relative to the total mass of the flux.

Description

Technical Field

[0001] The invention relates to a preparation method of a soldering flux, a solder paste and a joint body.

[0002] This application claims priority based on Japanese Patent Application No. 2022-118197 filed in Japan on July 25, 2022, and the contents are incorporated herein by reference. Background Art

[0003] Usually, fixing components to a substrate and electrically connecting components to the substrate are performed by soldering. In soldering, flux, solder powder, and solder paste mixed with flux and solder powder are used.

[0004] The flux has the ability to chemically remove metal oxides present on the metal surface of the object to be welded and in the solder, and to allow metal elements to move at the boundary between the two. Therefore, by using the flux for welding, an intermetallic compound is formed between the two, thereby obtaining a strong joint.

[0005] In soldering using solder paste, first, solder paste is printed on a substrate, components are mounted, and the substrate with components mounted is heated in a heating furnace called a reflow furnace, thereby melting solder powder contained in the solder paste and soldering the components to the substrate.

[0006] The flux used in reflow soldering usually contains resin components, solvents, activators, thixotropic agents, etc. In order to make the rheological properties of the flux such as viscosity and thixotropic ratio appropriate, rosin is added to the flux as a resin component. Rosin remains as flux residue after reflow soldering.

[0007] On the other hand, Patent Document 1 proposes a solder paste that does not contain rosin and thus reduces flux residue.

[0008] Prior art documents

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2006-289497 Summary of the invention

[0011] Problems to be solved by the present invention

[0012] However, in the solder paste using the flux described in Patent Document 1, it is difficult to suppress the heat collapse.

[0013] Therefore, an object of the present invention is to provide a flux, a solder paste, and a method for producing a joint body that can reduce flux residue and suppress heat collapse.

[0014] Means of solving the problem

[0015] The present invention includes the following aspects.

[0016] [1] A soldering flux comprising a first solvent and a thixotropic agent, wherein the first solvent has a viscosity of 10 Pa·s or more at 30°C or is solid at 30°C, the first solvent has a boiling point of 200°C or more, the weight reduction rate of the first solvent when heated to 230°C is less than 96% by mass, the thixotropic agent comprises a polyamide, the polyamide being one or more selected from a condensate of an aliphatic carboxylic acid and an amine, and a condensate of an aliphatic carboxylic acid, a hydroxyl-containing aliphatic carboxylic acid, and an amine, the content of the first solvent is 30% by mass or more relative to 100% by mass of the total mass of the soldering flux, and the content of the polyamide exceeds 2% by mass relative to 100% by mass of the total mass of the soldering flux.

[0017] [2] The soldering flux according to [1], further comprising a second solvent (excluding the solvent belonging to the first solvent), wherein the second solvent has a boiling point of 250° C. or higher and a relative dielectric constant of 6.0 or higher.

[0018] [3] The soldering flux according to [2], wherein the second solvent is a compound represented by the following general formula (1).

[0019] [Chemical formula 1]

[0020]

[0021] [Where R 1 represents a hydrocarbon group having 2 to 4 carbon atoms. 2 represents a hydrocarbon group having 4 to 10 carbon atoms. m is 1 to 3.]

[0022] [4] The soldering flux according to [2] or [3], wherein a mass ratio of the first solvent to the second solvent is 0.1 to 1.0 as expressed by a mass ratio of second solvent / first solvent.

[0023] [5] The soldering flux according to any one of [2] to [4], wherein the mass ratio of the polyamide to the second solvent is 0.15 to 0.4 in terms of the mass ratio represented by polyamide / second solvent.

[0024] [6] The soldering flux according to any one of [1] to [5], wherein the aliphatic carboxylic acid contains a dicarboxylic acid.

[0025] [7] A solder paste comprising a solder alloy powder and the flux according to any one of [1] to [6].

[0026] [8] A method for producing a bonded body, comprising the step of obtaining a bonded body by soldering a component to a substrate, wherein the soldering is performed by reflow soldering in a reducing gas atmosphere using the solder paste described in [7].

[0027] Effects of the Invention

[0028] According to the present invention, it is possible to provide a flux, a solder paste, and a method for producing a joint body that can reduce flux residue and suppress heat collapse. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a graph showing a DSC curve of the polyamide contained in the soldering flux according to one embodiment of the present invention.

[0030] Figure 2 This is a graph showing the relationship between the ratio of the amount of heat absorbed by the polyamide contained in the flux according to one embodiment of the present invention and the temperature.

[0031] Figure 3 This is a diagram schematically showing the pattern holes of I in the evaluation of the heat collapse suppressing ability. DETAILED DESCRIPTION

[0032] (Flux)

[0033] The soldering flux of this embodiment contains a first solvent and a thixotropic agent containing a specific polyamide. The soldering flux of this embodiment is suitable for reflow soldering.

[0034] The soldering flux of the present embodiment contains the first solvent and the specific polyamide, thereby reducing the amount of flux residue and easily providing the flux with predetermined rheological properties.

[0035] Reflow soldering includes, for example, the following steps. First, the substrate with components mounted thereon is heated at 150 to 180°C for 1 to 2 minutes (referred to as preheating). Next, the substrate is heated at a temperature from the liquidus temperature of the solder alloy to a temperature about 20°C higher than the liquidus temperature (referred to as the peak temperature) for about 1 minute (referred to as formal heating).

[0036] The flux of this embodiment is difficult to volatilize during preheating, so the first solvent is likely to remain after preheating and before formal heating. Therefore, it is easy to prevent the thixotropic agent, activator, etc. from drying up and becoming flux residue. The flux of this embodiment is difficult to volatilize during preheating, so it is easy to prevent the volatilization of the activator, etc. As a result, it is easy to maintain the effect of the activator, etc. In other words, it is easy to improve the heat resistance of the flux.

[0037] Furthermore, in the flux of the present embodiment, the first solvent is easily volatilized at a temperature near the peak temperature during the main heating of the reflow process. As a result, the amount of the solvent remaining after the reflow process is reduced, and thus the flux residue is easily reduced.

[0038] In addition, the flux of this embodiment can easily suppress heat collapse by containing a specific polyamide. Since the specific polyamide can easily improve the heat collapse suppression ability, the amount of addition required to obtain a predetermined heat collapse suppression ability can be reduced. As a result, the flux residue can be reduced.

[0039] <Solvent>

[0040] The First Solvent

[0041] The first solvent has a viscosity of 10 Pa·s or more at 30° C. or is solid at 30° C. The first solvent has a boiling point of 200° C. or more. The weight loss rate of the first solvent when heated to 230° C. is less than 96% by mass. The content of the first solvent is 30% by mass or more relative to the total mass (100% by mass) of the flux.

[0042] The first solvent has a viscosity of 10 Pa·s or more at 30° C. or is solid at 30° C. The first solvent may have a viscosity of 10 Pa·s or more and 5000 Pa·s or less, 10 Pa·s or more and 2000 Pa·s or less, or 10 Pa·s or more and 1000 Pa·s or less.

[0043] Therefore, even when the soldering flux does not contain rosin, the soldering flux of the present embodiment can easily maintain the rheological properties of the soldering flux at a predetermined level.

[0044] The viscosity is measured using a Brookfield viscometer.

[0045] In the present specification, "solid at 30°C" means having a melting point exceeding 30°C.

[0046] Here, the melting point refers to the temperature at which a solid melts to become a liquid. The values ​​of the melting points of compounds in this specification are mainly the values ​​described in "Chemical Handbook Basic Edition Revised 5th Edition".

[0047] The boiling point of the first solvent is 200° C. or higher, preferably 250° C. or higher, more preferably 280° C. or higher, and further preferably 300° C. or higher.

[0048] By setting the boiling point of the first solvent to be equal to or higher than the lower limit, the first solvent is likely to remain after preheating and before main heating. Therefore, the effects of the thixotropic agent, activator, etc. are likely to be maintained. As a result, after preheating and before main heating, the heat resistance of the flux is likely to be improved, and the thixotropic agent, activator, etc. are likely to be suppressed from solidifying and becoming flux residue.

[0049] The boiling point of the first solvent is preferably 450°C or lower, more preferably 410°C or lower, further preferably 370°C or lower, particularly preferably 330°C or lower.

[0050] By setting the boiling point of the first solvent to be below the upper limit, the flux can be easily volatilized during the main heating, thereby making it easy to reduce the flux residue after the main heating.

[0051] The boiling point of the first solvent is preferably 200°C to 450°C, more preferably 250°C to 410°C, further preferably 280°C to 370°C, and still further preferably 300°C to 370°C.

[0052] In this specification, the boiling point refers to the temperature of a liquid at which the saturated vapor pressure of the liquid is equal to 1 atmospheric pressure (ie, 1013 hPa).

[0053] The weight reduction rate of the first solvent when heated to 230° C. is less than 96% by mass, preferably less than 93% by mass, more preferably less than 90% by mass, further preferably less than 87% by mass, and particularly preferably less than 84% by mass.

[0054] By setting the weight reduction rate within the above range, the first solvent is likely to remain after preheating and before main heating. Therefore, the effects of the activator and the like are likely to be maintained. As a result, the heat resistance of the flux is likely to be improved after preheating and before main heating, and the thixotropic agent, activator and the like are likely to be prevented from solidifying and becoming flux residue.

[0055] The lower limit of the weight reduction rate of the first solvent when heated to 230° C. is not particularly limited as long as the effect of the present invention can be exhibited, and may be, for example, 50% by mass.

[0056] The weight reduction rate of the first solvent when heated to 230° C. is 50% by mass or more and less than 96% by mass, preferably 60% by mass or more and less than 93% by mass, more preferably 65% ​​by mass or more and less than 90% by mass, further preferably 70% by mass or more and less than 87% by mass, and particularly preferably 75% by mass or more and less than 84% by mass. Alternatively, the weight reduction rate of the first solvent when heated to 230° C. is preferably 81% by mass or more and 94% by mass or less.

[0057] In the present invention, the "weight reduction rate when heated to a specific temperature" is measured, for example, as follows.

[0058] Using a differential thermal-thermogravimetric simultaneous measuring apparatus (manufactured by Hitachi High-Tech Scientific Co., Ltd., STA7200), 10 mg of the sample to be measured was placed in an aluminum pan, and heating was started, and the temperature was raised to a specific temperature at 10°C / min. Then, the weight loss rate was calculated by the following calculation formula based on the mass W0 of the sample before heating and the mass W1 of the sample when the sample reached the specific temperature.

[0059] Weight reduction rate (mass %) = 100 × (W0-W1) / W0

[0060] Furthermore, the weight reduction rate of the first solvent when heated to 250° C. is preferably 95% by mass or more, more preferably 97% by mass or more, further preferably 98% by mass or more, and particularly preferably 99% by mass or more.

[0061] By setting the weight reduction rate of the first solvent when heated to 250° C. to be within the above range, the flux can be easily volatilized during reflow, thereby making it easier to reduce flux residue after reflow.

[0062] The upper limit of the weight reduction rate of the first solvent when heated to 250° C. is not particularly limited as long as the effect of the present invention can be exerted, and may be 100% by mass in terms of measurement.

[0063] The upper limit of the weight reduction rate of the first solvent when heated to 250°C is preferably 95% by mass or more and 100% by mass or less, more preferably 97% by mass or more and 100% by mass or less, further preferably 98% by mass or more and 100% by mass or less, and particularly preferably 99% by mass or more and 100% by mass or less.

[0064] The first solvent may be used alone or in combination of two or more.

[0065] Examples of the first solvent include isobornylcyclohexanol and trimethylolpropane, and isobornylcyclohexanol is preferred.

[0066] The content of the first solvent is 30 mass % or more, preferably 40 mass % or more, more preferably 50 mass % or more, further preferably 60 mass % or more, particularly preferably 70 mass % or more, based on the total mass (100 mass %) of the flux.

[0067] The content of the first solvent is preferably 95 mass % or less, more preferably 90 mass % or less, further preferably 85 mass % or less, particularly preferably 80 mass % or less, based on the total mass (100 mass %) of the flux.

[0068] The content of the first solvent is 30% by mass or more and 98% by mass or less, preferably 40% by mass or more and 95% by mass or less, more preferably 50% by mass or more and 90% by mass or less, further preferably 60% by mass or more and 85% by mass or less, and particularly preferably 70% by mass or more and 80% by mass or less, relative to the total mass (100% by mass) of the flux. In addition, the content of the first solvent is preferably 30% by mass or more and 86% by mass or more, and more preferably 40% by mass or more and 86% by mass or less.

[0069] 《Other solvents》

[0070] The soldering flux of the present embodiment may contain other solvents in addition to the first solvent.

[0071] Examples of other solvents include glycol ether solvents, alcohol solvents, terpineols, and ester solvents.

[0072] The other solvents may be used alone or in combination of two or more.

[0073] Examples of other solvents include the following solvents: The term in parentheses indicates the boiling point of the solvent.

[0074] Examples of glycol ether solvents include ethylene glycol monophenyl ether (237°C), diethylene glycol monobutyl ether (230.6°C), propylene glycol monophenyl ether (242°C), tripropylene glycol monomethyl ether (243°C), diethylene glycol monohexyl ether (259°C), diethylene glycol mono-2-ethylhexyl ether (275°C), diethylene glycol dibutyl ether (256°C), triethylene glycol monobutyl ether (278°C), triethylene glycol butyl methyl ether (261°C), tetraethylene glycol dimethyl ether (275°C), and tri(propylene glycol) n-butyl ether.

[0075] Examples of the alcohol solvent include 1,2-butanediol (192° C.), 2-methyl-2,4-pentanediol (197° C.), 2,3-dimethyl-2,3-butanediol (174° C.), 1-ethynyl-1-cyclohexanol (180° C.), 2,4-diethyl-1,5-pentanediol (338° C.), and 1,2,6-trihydroxyhexane.

[0076] Examples of the terpineols include α-terpineol (218° C.), β-terpineol (210° C.), γ-terpineol (218° C.), and a terpineol mixture (i.e., a mixture whose main component is α-terpineol and contains β-terpineol or γ-terpineol).

[0077] Examples of the ester solvent include bis(2-ethylhexyl) sebacate.

[0078] (Second Solvent)

[0079] The soldering flux of the present embodiment may contain a second solvent in addition to the first solvent.

[0080] The second solvent has a boiling point of 250° C. or higher and a relative dielectric constant of 6.0 or higher.

[0081] The boiling point of the second solvent is preferably 250°C or higher and 350°C or lower, and more preferably 250°C or higher and 300°C or lower.

[0082] The relative dielectric constant of the second solvent is preferably 6.0 to 50, more preferably 6.0 to 30, further preferably 6.0 to 20, further preferably 6.0 to 15, particularly preferably 6.0 to 9.0.

[0083] Here, the relative dielectric constant was measured based on JIS C2565 (1992) at a measurement frequency of 1 GHz. 010 The resonator is positioned such that the sample is mounted at the center of the resonator so that it is aligned with the axis of the resonator, and an external magnetic field is applied in the axial direction of the sample. The external magnetic field is applied until no change in the measured value is observed even if the magnetic field changes, and the resonant frequency f1 is measured. The frequency f0 is measured in the same manner except that the sample is not mounted on the resonator. In addition, the parameter C is calculated using the electromagnetic field analysis software SIMULIA CST Studio Suite (Dassault Systemes Simulia Corporation), and the relative dielectric constant ε is calculated according to the following formula r .

[0084] [Mathematical formula 1]

[0085]

[0086] The soldering flux of this embodiment uses the first solvent and the second solvent together, so that the solder paste printed on the substrate is not easy to volatilize during storage. As a result, it is easy to suppress the decrease in viscosity of the solder paste containing the soldering flux, and it is easy to improve the assembly of components on the substrate printed with the solder paste containing the soldering flux.

[0087] As the second solvent, a compound represented by the following general formula (1) is preferred.

[0088] [Chemical formula 2]

[0089]

[0090] In formula (1), R 1 represents a hydrocarbon group having 2 to 4 carbon atoms.2 It represents a hydrocarbon group having 4 to 10 carbon atoms. m is 1 to 3.

[0091] R 1 The hydrocarbon group in may be an aliphatic hydrocarbon group. The aliphatic hydrocarbon group may be saturated or unsaturated, and is usually preferably saturated.

[0092] Examples of the aliphatic hydrocarbon group include a linear or branched aliphatic hydrocarbon group and an aliphatic hydrocarbon group containing a ring in the structure, and a linear aliphatic hydrocarbon group is preferred.

[0093] The linear or branched aliphatic hydrocarbon group preferably has 2 to 3 carbon atoms, more preferably 2 carbon atoms.

[0094] As R 1 The straight-chain aliphatic hydrocarbon group is preferably a straight-chain alkylene group, and specific examples include methylene [-CH2-], ethylene [-(CH2)2-], trimethylene [-(CH2)3-], tetramethylene [-(CH2)4-], etc., and ethylene [-(CH2)2-] is preferred.

[0095] As R 1 The branched aliphatic hydrocarbon group in the invention is preferably a branched alkylene group, and specifically, alkylmethylene groups such as -CH(CH3)-, -CH2-CH(CH3)-, -CH(CH2CH3)-, -C(CH3)2-, and -C(CH3)(CH2CH3); alkylethylene groups such as -CH(CH3)CH2-, -CH(CH3)CH(CH3)-, -C(CH3)2CH2-, and -CH(CH2CH3)CH2-; alkyltrimethylene groups such as -CH(CH3)CH2CH2-, and -CH2CH(CH3)CH2- are preferably -CH2-CH(CH3)-.

[0096] R 2 The hydrocarbon group in may be an aliphatic hydrocarbon group. The aliphatic hydrocarbon group may be saturated or unsaturated, and is usually preferably saturated.

[0097] More specifically, examples of the aliphatic hydrocarbon group include a linear or branched aliphatic hydrocarbon group, and an aliphatic hydrocarbon group containing a ring in its structure.

[0098] R 2 The number of carbon atoms of the hydrocarbon group in is preferably 4-8, more preferably 5-7, most preferably 6.

[0099] The compound represented by the general formula (1) is preferably diethylene glycol monohexyl ether.

[0100] In the general formula (1), R of diethylene glycol monohexyl ether is1 is ethylene, R 2 It is a straight-chain hexyl group, and m is 2.

[0101] The content of the second solvent is preferably 60 mass % or less, more preferably 50 mass % or less, further preferably 40 mass % or less, particularly preferably 30 mass % or less, and most preferably 25 mass % or less, relative to the total mass of the flux (100 mass %).

[0102] By setting the content of the second solvent to be equal to or less than the above upper limit, it is easy to improve the ability to suppress heat collapse and the ability to suppress solder ball generation.

[0103] The content of the second solvent is preferably 5% by mass or more, and more preferably 10% by mass or more, based on the total mass (100% by mass) of the flux.

[0104] By setting the content of the second solvent to be equal to or greater than the lower limit, the viscosity of the solder paste containing the flux can be easily increased, and the assembly properties of components on a substrate on which the solder paste containing the flux is printed can be easily improved.

[0105] The content of the second solvent, relative to the total mass (100 mass%) of the flux, is preferably 5 mass% to 60 mass%, more preferably 5 mass% to 50 mass%, further preferably 10 mass% to 46 mass%, further preferably 10 mass% to 40 mass%, particularly preferably 10 mass% to 30 mass%, and most preferably 10 mass% to 25 mass%.

[0106] In the soldering flux, the mass ratio of the first solvent to the second solvent is preferably 0.1 to 1.0 in terms of mass ratio represented by second solvent / first solvent, that is, ratio of the total mass of the second solvent to the total mass of the first solvent.

[0107] When the mass ratio represented by the second solvent / the first solvent is within the above range, the viscosity of the flux can be easily increased, and the assembly properties of components on a substrate printed with the solder paste containing the flux can be easily improved.

[0108] Of all the solvents in the flux of the present embodiment, the total content of the first solvent and the second solvent is preferably 65 mass % or more and 100 mass % or less, more preferably 75 mass % or more and 100 mass % or less, further preferably 85 mass % or more and 100 mass % or less, and even more preferably 100 mass % with respect to the total mass (100 mass %) of all the solvents.

[0109] When the total content of the first solvent and the second solvent in all solvents of the soldering flux is within the above range, the viscosity of the soldering flux can be easily increased, and the assembly performance of components on a substrate printed with a solder paste containing the soldering flux can be easily improved.

[0110] <Thixotropic agent>

[0111] The soldering flux of the present embodiment contains a thixotropic agent containing a specific polyamide.

[0112] Polyamide

[0113] In this specification, the specific polyamide refers to an amide having three or more amide bonds in the molecule.

[0114] The content of the specific polyamide exceeds 2% by mass based on the total amount (100% by mass) of the soldering flux.

[0115] The specific polyamide is at least one selected from "condensates of aliphatic carboxylic acids and amines" and "condensates of hydroxyl-containing aliphatic carboxylic acids, aliphatic carboxylic acids and amines", and is preferably "condensates of hydroxyl-containing aliphatic carboxylic acids, aliphatic carboxylic acids and amines".

[0116] The aliphatic carboxylic acid from which the specific polyamide is derived may be used alone or in combination of two or more.

[0117] Examples of the aliphatic carboxylic acid include monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, etc. The aliphatic carboxylic acid is preferably a monocarboxylic acid or a dicarboxylic acid, and more preferably a dicarboxylic acid.

[0118] The hydrocarbon group of the aliphatic carboxylic acid may be any of linear, branched or cyclic. The hydrocarbon group is preferably linear or branched, more preferably linear.

[0119] The hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group, and is preferably a saturated hydrocarbon group.

[0120] The aliphatic monocarboxylic acid has preferably 12 to 22 carbon atoms, more preferably 14 to 22 carbon atoms, and even more preferably 16 to 22 carbon atoms.

[0121] Examples of the aliphatic monocarboxylic acid include lauric acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, etc. The aliphatic monocarboxylic acid is preferably palmitic acid or stearic acid.

[0122] The aliphatic dicarboxylic acid has preferably 2 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, and even more preferably 8 to 14 carbon atoms.

[0123] Examples of the aliphatic dicarboxylic acid include adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, and pentadecanedioic acid. The aliphatic dicarboxylic acid is preferably suberic acid, azelaic acid, sebacic acid, undecanedioic acid, or dodecanedioic acid, more preferably sebacic acid or dodecanedioic acid, and even more preferably dodecanedioic acid.

[0124] The aliphatic carboxylic acid preferably contains an aliphatic dicarboxylic acid. The aliphatic carboxylic acid may contain one or more selected from sebacic acid and dodecanedioic acid, and one or more selected from palmitic acid and stearic acid.

[0125] The hydroxyl-containing aliphatic carboxylic acid from which the specific polyamide is derived may be used alone or in combination of two or more.

[0126] The hydrocarbon group of the hydroxyl-containing aliphatic carboxylic acid may be any of linear, branched or cyclic. The hydrocarbon group is preferably linear or branched, more preferably linear.

[0127] The hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group, and is preferably a saturated hydrocarbon group.

[0128] The hydroxyl group-containing aliphatic carboxylic acid preferably has 10 to 25 carbon atoms, and more preferably 15 to 21 carbon atoms.

[0129] Examples of the hydroxyl-containing aliphatic carboxylic acid include hydroxypentadecanoic acid, hydroxyhexadecanoic acid, hydroxyheptadecanoic acid, hydroxyoctadecanoic acid (hydroxystearic acid), hydroxyeicosanoic acid, and hydroxyheneicosanoic acid. The hydroxyl-containing aliphatic carboxylic acid is preferably hydroxystearic acid, and more preferably 12-hydroxystearic acid.

[0130] The amines from which the specific polyamide is derived may be used alone or in combination of two or more.

[0131] Examples of the amine include aliphatic amines and aromatic amines, and the amine is preferably an aliphatic amine.

[0132] Examples of the amine include monoamine, diamine, triamine, tetraamine, etc. The amine is preferably a diamine.

[0133] The hydrocarbon group of the aliphatic amine may be any of linear, branched or cyclic. The hydrocarbon group is preferably linear or branched, more preferably linear. The number of carbon atoms of the aliphatic amine is preferably 3 to 10, more preferably 4 to 8.

[0134] The hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group, and is preferably a saturated hydrocarbon group.

[0135] Examples of the amine include ethylenediamine, 1,3-propylenediamine, 1,4-butylenediamine, hexamethylenediamine, m-xylenediamine, toluenediamine, p-xylenediamine, phenylenediamine, isophoronediamine, 1,10-decanediamine, 1,12-dodecanediamine, 4,4'-diaminodicyclohexylmethane, 4,4'-diaminodiphenylmethane, butane-1,1,4,4-tetramine, and pyrimidine-2,4,5,6-tetramine. The amine is preferably hexamethylenediamine.

[0136] The temperature of the endothermic peak of the specific polyamide can be measured by DSC (Differential Scanning Calorimetry).

[0137] A specific method for measuring the endothermic peak is as follows: in a nitrogen atmosphere, the temperature is raised at a rate of 20°C / min, and about 10 mg of polyamide is heated from 25°C to 350°C, and the measurement is performed. As a measuring instrument, DSC7020 (manufactured by Hitachi High-Tech Scientific) can be used. In this specification, the temperature of the endothermic peak refers to the temperature of the peak top.

[0138] The specific polyamide used in the soldering flux of the present embodiment has one or two or more endothermic peaks in the temperature range of 120° C. to 200° C. inclusive.

[0139] When the number of endothermic peaks is one, the temperature of the endothermic peak is preferably 150°C to 200°C, more preferably 160°C to 200°C, further preferably 170°C to 200°C, particularly preferably 180°C to 200°C.

[0140] When the number of endothermic peaks is 2 or more, for a specific polyamide, for example, the lowest temperature endothermic peak may be in the range of 120°C to 200°C, the highest temperature endothermic peak may be in the range of 120°C to 200°C, or all the endothermic peaks may be in the range of 120°C to 200°C.

[0141] The temperature of the maximum endothermic peak is preferably 150°C to 200°C, more preferably 160°C to 200°C, further preferably 170°C to 200°C, particularly preferably 180°C to 200°C.

[0142] In the measurement by DSC, the ratio of the heat absorption amount of the specific polyamide in the range of 160°C to 200°C to the total heat absorption amount in the range of 50°C to 200°C is preferably 30% or more, more preferably 40% or more, and further preferably 45% or more.

[0143] By setting the ratio of the heat absorption amount in the range of 160°C to 200°C in the measurement by DSC of the specific polyamide to be above the lower limit, the heat collapse during reflow can be sufficiently suppressed. In particular, even when the preheating temperature is increased, for example, 190°C or more, and further 200°C or more, the heat collapse can be suppressed.

[0144] In this specification, the endothermic amount of a specific polyamide can be calculated from the peak area of ​​a DSC curve of the specific polyamide.

[0145] In the DSC measurement of the specific polyamide, the ratio of the endothermic amount in the range of 50°C to 150°C to the total endothermic amount in the range of 50°C to 200°C is preferably 80% or less, more preferably 60% or less, and further preferably 50% or less.

[0146] The lower limit of the ratio of the amount of heat absorption is not particularly limited as long as the effect of the present invention can be achieved, and may be, for example, 10% or more, 20% or more, or 30% or more.

[0147] The ratio of the amount of heat absorbed is preferably 10% to 80%, more preferably 10% to 60%, and even more preferably 10% to 50%. Alternatively, the ratio of the amount of heat absorbed is preferably 20% to 80%, more preferably 20% to 60%, and even more preferably 30% to 50%.

[0148] In the DSC measurement of the specific polyamide, the ratio of the endothermic amount in the range of 50°C to 180°C to the total endothermic amount in the range of 50°C to 200°C is preferably 95% or less, more preferably 90% or less, and further preferably 85% or less.

[0149] The lower limit of the ratio of the amount of heat absorbed is not particularly limited as long as the effect of the present invention can be achieved, and may be, for example, 40% or more, 50% or more, or 60% or more.

[0150] The ratio of the amount of heat absorbed is preferably 40% to 95%, more preferably 40% to 90%, and even more preferably 40% to 85%. Alternatively, the ratio of the amount of heat absorbed is preferably 50% to 95%, more preferably 50% to 90%, and even more preferably 60% to 85%.

[0151] From the viewpoint of further improving the ability to suppress the heat collapse, the specific polyamide contained in the flux of the present embodiment is preferably a condensate of an aliphatic carboxylic acid, a hydroxyl group-containing aliphatic monocarboxylic acid, and an amine.

[0152] The specific polyamide contained in the soldering flux of the present embodiment is more preferably a condensate of an aliphatic dicarboxylic acid, a hydroxyl group-containing aliphatic monocarboxylic acid, and a diamine.

[0153] The specific polyamide contained in the soldering flux of the present embodiment is more preferably a condensate of an aliphatic dicarboxylic acid having 8 to 14 carbon atoms, a hydroxyl group-containing aliphatic monocarboxylic acid having 15 to 21 carbon atoms, and an aliphatic diamine having 4 to 8 carbon atoms.

[0154] Among them, the specific polyamide is particularly preferably a condensate of at least one selected from sebacic acid and dodecanedioic acid, 12-hydroxystearic acid, and hexamethylenediamine.

[0155] The specific polyamide may be a condensate of one or more selected from sebacic acid and dodecanedioic acid, one selected from palmitic acid and stearic acid, 12-hydroxystearic acid, and hexamethylenediamine.

[0156] When the specific polyamide is a condensate of an aliphatic dicarboxylic acid, a hydroxyl group-containing aliphatic monocarboxylic acid, and an aliphatic diamine, the molar ratio of these raw materials preferably satisfies the following relationship.

[0157] Here, the aliphatic dicarboxylic acid used as the raw material of the specific polyamide is X mol, the hydroxyl group-containing aliphatic monocarboxylic acid is Y mol, and the aliphatic diamine is Z mol.

[0158] Preferably, the total number of moles of amino groups in the compounds contained in the raw material is equal to the total number of moles of carboxyl groups, or the total number of moles of amino groups in the compounds contained in the raw material is less than the total number of moles of carboxyl groups. Specifically, it is preferred that 2Z≤2X+Y is satisfied.

[0159] The relationship of the molar ratios of the raw materials is preferably 0.2Y≤X≤2Y, and more preferably 0.4Y≤X≤1.5Y.

[0160] The relationship of the molar ratios of the raw materials is preferably 0.5Y≤Z≤2Y, and more preferably 0.8Y≤Z≤1.8Y.

[0161] The content of the specific polyamide in the soldering flux exceeds 2 mass %, more preferably 3 mass % or more, further preferably 4 mass % or more, and particularly preferably 5 mass % or more, based on the total amount (100 mass %) of the soldering flux.

[0162] By setting the content of the specific polyamide to be equal to or more than the above lower limit, the ability to suppress heat collapse and the ability to suppress solder ball generation can be easily improved.

[0163] The upper limit of the content of the specific polyamide in the flux is not particularly limited as long as the effect of the present invention is achieved. The content of the specific polyamide can be 15% by mass relative to the total amount of the flux (100% by mass), preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 7% by mass or less.

[0164] By setting the content of the specific polyamide to be equal to or less than the above upper limit, it is easier to reduce the flux residue.

[0165] The content of the specific polyamide in the flux is greater than 2 mass % and less than 15 mass %, more preferably greater than 3 mass % and less than 10 mass %, further preferably greater than 4 mass % and less than 8 mass %, and particularly preferably greater than 4 mass % and less than 5 mass %, relative to the total amount of the flux (100 mass %).

[0166] In the soldering flux, the mass ratio of the specific polyamide to the second solvent is preferably 0.08 to 0.4, more preferably 0.15 to 0.4, expressed as a mass ratio of specific polyamide / second solvent, that is, a ratio of the total mass of the specific polyamide to the total mass of the second solvent.

[0167] By setting the mass ratio represented by the specific polyamide / the second solvent to be within the above range, it is easy to improve the ability to suppress heat collapse and the ability to suppress solder ball generation.

[0168] 《Other Thixotropic Agents》

[0169] The thixotropic agent may contain other thixotropic agents in addition to the polyamide.

[0170] Examples of other thixotropic agents include amide-based thixotropic agents other than those described above, wax-based thixotropic agents, and sorbitol-based thixotropic agents.

[0171] The other thixotropic agents may be used alone or in combination of two or more.

[0172] Examples of amide-based thixotropic agents other than those described above include monoamides, bisamides, and other polyamides.

[0173] Examples of the monoamide include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, saturated fatty acid amide, oleic acid amide, erucic acid amide, unsaturated fatty acid amide, p-toluamide, p-toluene methane amide, aromatic amide, hexamethylene hydroxystearic acid amide, substituted amides, hydroxymethyl stearic acid amide, hydroxymethyl amide, and fatty acid ester amides.

[0174] Examples of the bisamides include methylene bisstearic acid amide, ethylene bislauric acid amide, ethylene bishydroxy fatty acid (fatty acid having carbon number of C6 to 24) amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, saturated fatty acid bisamides, methylene bisoleic acid amide, unsaturated fatty acid bisamides, meta-xylylene bisstearic acid amide, and aromatic bisamides.

[0175] Examples of other polyamides include saturated fatty acid polyamides, unsaturated fatty acid polyamides, aromatic polyamides, 1,2,3-propanetricarboxylic acid tris(2-methylcyclohexylamide), cyclic amide oligomers, and non-cyclic amide oligomers.

[0176] Examples of the cyclic amide oligomer include amide oligomers obtained by polycondensation of dicarboxylic acid and diamine into a ring, amide oligomers obtained by polycondensation of tricarboxylic acid and diamine into a ring, amide oligomers obtained by polycondensation of dicarboxylic acid and triamine into a ring, amide oligomers obtained by polycondensation of tricarboxylic acid and triamine into a ring, amide oligomers obtained by polycondensation of dicarboxylic acid, tricarboxylic acid and diamine into a ring, amide oligomers obtained by polycondensation of dicarboxylic acid, tricarboxylic acid and triamine into a ring, amide oligomers obtained by polycondensation of dicarboxylic acid, diamine and triamine into a ring, amide oligomers obtained by polycondensation of tricarboxylic acid, diamine and triamine into a ring, and amide oligomers obtained by polycondensation of dicarboxylic acid, tricarboxylic acid, diamine and triamine into a ring.

[0177] In addition, the non-cyclic amide oligomer can include the situation that monocarboxylic acid and diamine and / or triamine are polycondensed into non-cyclic and the amide oligomer obtained, the situation that dicarboxylic acid and / or tricarboxylic acid and monoamine are polycondensed into non-cyclic and the amide oligomer obtained, etc. In the case of the amide oligomer containing monocarboxylic acid or monoamine, monocarboxylic acid and monoamine function as terminal molecules (terminal molecules) to become the non-cyclic amide oligomer with reduced molecular weight. In addition, in the case of the amide compound obtained by polycondensing dicarboxylic acid and / or tricarboxylic acid with diamine and / or triamine into non-cyclic, the non-cyclic amide oligomer becomes a non-cyclic high molecular system amide polymer. In addition, the non-cyclic amide oligomer also includes the amide oligomer obtained by condensing monocarboxylic acid and monoamine into non-cyclic.

[0178] Examples of the wax-based thixotropic agent include ester compounds, and specific examples include hydrogenated castor oil and the like.

[0179] Examples of the sorbitol-based thixotropic agent include dibenzylidene-D-sorbitol, di(4-methylbenzylidene)-D-sorbitol, (D-)sorbitol, monobenzylidene (-D-)sorbitol, and mono(4-methylbenzylidene)-(D-)sorbitol.

[0180] <Other ingredients>

[0181] The soldering flux of the present embodiment may contain other components as necessary in addition to the solvent and the thixotropic agent.

[0182] Examples of other components include activators such as organic acids, amines, and halogen compounds, surfactants, metal deactivators, antioxidants, silane coupling agents, and colorants.

[0183] Active Agent

[0184] Examples of the activator include organic acids, amines, and halogen compounds.

[0185] [Organic acid]

[0186] Examples of the organic acid include carboxylic acid, organic sulfonic acid, etc. Examples of the carboxylic acid include aliphatic carboxylic acid, aromatic carboxylic acid, etc. Examples of the aliphatic carboxylic acid include aliphatic monocarboxylic acid, aliphatic dicarboxylic acid, etc.

[0187] Examples of the aliphatic monocarboxylic acid include hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, isononanoic acid, decanoic acid, decenoic acid, lauric acid (dodecanoic acid), undecanoic acid, heneicosanoic acid, tridecanoic acid, myristoleic acid, pentadecanoic acid, isopalmitic acid, palmitoleic acid, hexadecatrienoic acid, cyclopentenonedecanoic acid, heptadecanoic acid, isostearic acid, elaidic acid, petroselinic acid, stearatetraenoic acid, eleostearic acid, tarric acid,

[0188] Octadecanoic acid, ricinoleic acid, vernolic acid, sterculic acid, nonadecanoic acid, eicosanoic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, myristic acid, etc.

[0189] Examples of the aliphatic dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, eicosanedioic acid, tartaric acid, 2,4-diethylglutaric acid, diglycolic acid, 2-methylnonanedioic acid, 4-(methoxycarbonyl)-2,4-dimethylundecanedioic acid, 4,6-di(methoxycarbonyl)-2,4,6-trimethyltridecanedioic acid, and 8,9-di(methoxycarbonyl)-8,9-dimethylhexadecanedioic acid.

[0190] Examples of the aromatic carboxylic acid include salicylic acid, dibutylaniline diglycolic acid, terephthalic acid, p-hydroxyphenylacetic acid, phenylsuccinic acid, phthalic acid, benzoic acid, 2,3-dihydroxybenzoic acid, 2-quinolinecarboxylic acid, 3-hydroxybenzoic acid, and p-anisic acid.

[0191] Examples of the carboxylic acid include tris(2-carboxyethyl)isocyanurate and 1,3-cyclohexanedicarboxylic acid.

[0192] Examples of the carboxylic acid include compounds represented by the following general formula (c1).

[0193] R 11 -COOH·(c1)

[0194] [Where R 11 represents a chain hydrocarbon group having 2 to 15 carbon atoms, an alicyclic hydrocarbon group having 3 to 15 carbon atoms, or an aromatic group. 11 Contains hydroxyl groups.]

[0195] R 11 The chain hydrocarbon group in may be either linear or branched.

[0196] The chain hydrocarbon group and the alicyclic hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group, and are preferably saturated hydrocarbon groups.

[0197] The number of carbon atoms in the chain hydrocarbon group is preferably 2-12, more preferably 3-9, particularly preferably 3-7, and most preferably 3-5.

[0198] Examples of the chain hydrocarbon group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, tert-pentyl, neopentyl, n-hexyl, isohexyl, sec-hexyl, tert-hexyl and neohexyl.

[0199] The alicyclic hydrocarbon group preferably has 3 to 12 carbon atoms, more preferably 4 to 12 carbon atoms, and even more preferably 4 to 8 carbon atoms.

[0200] Examples of the alicyclic hydrocarbon group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, and a cycloundecyl group.

[0201] R 11 The aromatic group in the above-mentioned group is a group having at least one aromatic ring, for example, an aromatic hydrocarbon ring of benzene, naphthalene, anthracene, phenanthrene, etc., an aromatic heterocyclic ring in which a part of the carbon atoms constituting the aromatic hydrocarbon ring are substituted by heteroatoms, a condensed ring formed by condensation of an aromatic hydrocarbon ring and an aromatic heterocyclic ring, etc.

[0202] R 11 When the aromatic group in has a substituent, examples of the substituent include a hydrocarbon group having 1 to 20 carbon atoms, an aromatic hydrocarbon group, a carboxyl group, a hydroxyl group, an amino group, a halogen atom, and the like, preferably a carboxyl group or a hydroxyl group.

[0203] Examples of the organic acid represented by the general formula (c1) include hydroxycarboxylic acids.

[0204] Examples of the hydroxycarboxylic acid include 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butyric acid, citric acid, isocitric acid, malic acid, and tartaric acid, and 2,2-bis(hydroxymethyl)propionic acid is preferred.

[0205] Examples of the carboxylic acid 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.

[0206] Examples of the dimer acid and trimer acid include a dimer acid as a reaction product of oleic acid and linoleic acid, a trimer acid as a reaction product of oleic acid and linoleic acid, a dimer acid as a reaction product of acrylic acid, a trimer acid as a reaction product of acrylic acid, a dimer acid as a reaction product of methacrylic acid, a trimer acid as a reaction product of methacrylic acid, a dimer acid as a reaction product of acrylic acid and methacrylic acid, a trimer acid as a reaction product of acrylic acid and methacrylic acid, a dimer acid as a reaction product of oleic acid, a trimer acid as a reaction product of oleic acid, a dimer acid as a reaction product of linoleic acid, a trimer acid as a reaction product of linolenic acid, a dimer acid as a reaction product of linolenic acid, a trimer acid as a reaction product of linolenic acid, a dimer acid as a reaction product of acrylic acid and oleic acid, a trimer acid as a reaction product of acrylic acid and linoleic acid, and a dimer acid as a reaction product of acrylic acid and oleic acid. Acid, trimer acid which is a reaction product of acrylic acid and linoleic acid, dimer acid which is a reaction product of acrylic acid and linolenic acid, trimer acid which is a reaction product of acrylic acid and linolenic acid, dimer acid which is a reaction product of methacrylic acid and oleic acid, trimer acid which is a reaction product of methacrylic acid and oleic acid, dimer acid which is a reaction product of methacrylic acid and linoleic acid, trimer acid which is a reaction product of methacrylic acid and linoleic acid, dimer acid which is a reaction product of methacrylic acid and linoleic acid, trimer acid which is a reaction product of methacrylic acid and linolenic acid, dimer acid which is a reaction product of oleic acid and linolenic acid, trimer acid which is a reaction product of linoleic acid and linolenic acid, dimer acid which is a reaction product of linoleic acid and linolenic acid, trimer acid which is a reaction product of linoleic acid and linolenic acid, hydrogenated dimer acid which is a hydrogenated product of the above dimer acids, hydrogenated trimer acid which is a hydrogenated product of the above trimer acids, and the like.

[0207] For example, the dimer acid, which is a reaction product of oleic acid and linoleic acid, is a dimer having 36 carbon atoms. Also, the trimer acid, which is a reaction product of oleic acid and linoleic acid, is a trimer having 54 carbon atoms.

[0208] Examples of the carboxylic acid include compounds represented by the following general formula (a1).

[0209] [Chemical formula 3]

[0210]

[0211] In formula (a1), Ra1 , R a2 , R a3 and R a4 Each independently represents a hydrocarbon group, a hydroxyl group, a halogen atom or a hydrogen atom.

[0212] As R a1 , R a2 , R a3 and R a4 The hydrocarbon group in "" includes a chain hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, an alicyclic hydrocarbon group having 3 to 20 carbon atoms which may have a substituent, an amino group, a hydroxyl group, a carboxyl group and the like.

[0213] The chain hydrocarbon group may be straight chain or branched chain. The chain hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group, preferably a saturated hydrocarbon group.

[0214] The alicyclic hydrocarbon group may be a polycyclic group or a monocyclic group. As a monocyclic alicyclic hydrocarbon group, a group formed by removing one or more hydrogen atoms from a monocycloalkane is preferred. As a polycyclic alicyclic hydrocarbon group, a group formed by removing one or more hydrogen atoms from a polycycloalkane is preferred.

[0215] As R a1 , R a2 , R a3 and R a4 The substituent that the hydrocarbon group in may have includes an amino group, a hydroxyl group, a carboxyl group, an acyl group, an alkoxy group, a carbonyl group, a halogen atom and the like.

[0216] The hydrocarbon group is preferably a chain hydrocarbon group having 1 to 5 carbon atoms which may have a substituent or a carboxyl group. Examples of the chain hydrocarbon group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, tert-pentyl, and neopentyl. The hydrocarbon group is preferably a carboxyl group.

[0217] Examples of the compound represented by the general formula (a1) include picolinic acid, dipicolinic acid, and 3-hydroxypicolinic acid.

[0218] Picolinic acid is R in the above general formula (a1) a1 , R a2 , R a3 and R a4 A compound containing hydrogen atoms.

[0219] 3-Hydroxypicolinic acid is R a1 is hydroxyl and R a2 , R a3 and R a4 A compound containing hydrogen atoms.

[0220] Examples of the organic sulfonic acid include aliphatic sulfonic acid, aromatic sulfonic acid, etc. Examples of the aliphatic sulfonic acid include alkane sulfonic acid, alkanol sulfonic acid, etc.

[0221] Examples of the alkanesulfonic acid include methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, 2-propanesulfonic acid, 1-butanesulfonic acid, 2-butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid, decanesulfonic acid, and dodecanesulfonic acid.

[0222] Examples of the alkanol sulfonic acid include 2-hydroxyethane-1-sulfonic acid, 2-hydroxypropane-1-sulfonic acid, 2-hydroxybutane-1-sulfonic acid, 2-hydroxypentane-1-sulfonic acid, 1-hydroxypropane-2-sulfonic acid, 3-hydroxypropane-1-sulfonic acid, 4-hydroxybutane-1-sulfonic acid, 2-hydroxyhexane-1-sulfonic acid, 2-hydroxydecane-1-sulfonic acid and 2-hydroxydodecane-1-sulfonic acid.

[0223] Examples of the aromatic sulfonic acid include 1-naphthalenesulfonic acid, 2-naphthalenesulfonic acid, p-toluenesulfonic acid, xylenesulfonic acid, p-phenolsulfonic acid, cresolsulfonic acid, sulfosalicylic acid, nitrobenzenesulfonic acid, sulfobenzoic acid, and diphenylamine-4-sulfonic acid.

[0224] The organic acid may be used alone or in combination of two or more.

[0225] As the organic acid, an aliphatic carboxylic acid is preferred, and an aliphatic dicarboxylic acid is more preferred.

[0226] The organic acid is preferably an aliphatic dicarboxylic acid, and preferably contains at least one selected from diglycolic acid, 2-methylazelaic acid, 4-(methoxycarbonyl)-2,4-dimethylundecanedioic acid, 4,6-di(methoxycarbonyl)-2,4,6-trimethyltridecanedioic acid and 8,9-di(methoxycarbonyl)-8,9-dimethylhexadecanedioic acid, and more preferably contains at least one selected from diglycolic acid and an organic acid mixture consisting of 2-methylazelaic acid, 4-(methoxycarbonyl)-2,4-dimethylundecanedioic acid, 4,6-di(methoxycarbonyl)-2,4,6-trimethyltridecanedioic acid and 8,9-di(methoxycarbonyl)-8,9-dimethylhexadecanedioic acid.

[0227] [amine]

[0228] Examples of the amine include azoles, guanidines, amino alcohols, alkylamine compounds, and amine polyoxyalkylene adducts.

[0229] Examples of the 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, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole trimellitate, 1-cyanoethyl-2-phenylimidazole trimellitate, 2,4-diamino-6-[2′-methylimidazolyl-(1′)]-ethyl tris-imidazolyl 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-benzylimidazole 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, 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-pentylphenyl)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, 5-phenyltetrazolyl, etc.

[0230] Examples of the guanidines include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylguanidine, 1,3-di-o-isopropylphenylguanidine, and 1,3-di-o-isopropylphenyl-2-propionylguanidine.

[0231] Examples of the amino alcohol 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.

[0232] Examples of the alkylamine compound include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, and stearylamine.

[0233] Examples of the amine polyoxyalkylene adduct include terminal diamine polyalkylene glycol, aliphatic amine polyoxyalkylene adduct, aromatic amine polyoxyalkylene adduct, and polyamine polyoxyalkylene adduct.

[0234] Examples of the alkylene oxide added to the amine polyoxyalkylene adduct include ethylene oxide, propylene oxide, and butylene oxide.

[0235] The terminal diamine polyalkylene glycol is a compound in which both ends of a polyalkylene glycol are amino-modified.

[0236] Examples of the terminal diamine polyalkylene glycol include terminal diamine polyethylene glycol, terminal diamine polypropylene glycol, and terminal diamine polyethylene glycol-polypropylene glycol copolymers.

[0237] Examples of the terminal diamine polyethylene glycol-polypropylene glycol copolymer include polyethylene glycol-polypropylene glycol copolymer bis(2-aminopropyl) ether and polyethylene glycol-polypropylene glycol copolymer bis(2-aminoethyl) ether.

[0238] Aliphatic amine polyoxyalkylene adducts, aromatic amine polyoxyalkylene adducts and polyamine polyoxyalkylene adducts are adducts in which a polyoxyalkylene group is bonded to the nitrogen atom of the amine. Examples of the amine include ethylenediamine, 1,3-propylenediamine, 1,4-butylenediamine, hexamethylenediamine, diethylenetriamine, laurylamine, stearylamine, oleylamine, tallowamine, cured tallowamine, tallowpropyldiamine, m-xylenediamine, toluenediamine, p-xylenediamine, phenylenediamine, isophoronediamine, 1,10-decanediamine, 1,12-dodecanediamine, 4,4-diaminodicyclohexylmethane, 4,4-diaminodiphenylmethane, butane-1,1,4,4-tetraamine, and pyrimidine-2,4,5,6-tetraamine.

[0239] The amines may be used alone or in combination of two or more.

[0240] The soldering flux of this embodiment preferably does not contain a resin component. By not containing a resin component, the amount of the soldering flux residue can be easily reduced.

[0241] In the present specification, examples of the resin component include rosin and resins other than rosin.

[0242] In the present specification, the term "rosin" includes natural resins containing abietic acid as a main component, mixtures of abietic acid and isomers thereof, and resins obtained by chemically modifying natural resins (sometimes referred to as rosin derivatives).

[0243] Examples of the rosin derivatives include purified rosin and modified rosin.

[0244] Examples of the modified rosin include hydrogenated rosin, polymerized rosin, polymerized hydrogenated rosin, disproportionated rosin, acid-modified rosin, rosin ester, acid-modified hydrogenated rosin, acid-modified disproportionated rosin, acid-anhydride-modified disproportionated rosin, phenol-modified rosin, and α,β-unsaturated carboxylic acid-modified products (acrylated rosin, maleated rosin, fumarated rosin, etc.), as well as purified products, hydrogenated products and disproportionated products of polymerized rosin, purified products, hydrogenated products and disproportionated products of 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.

[0245] 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.

[0246] Examples of modified terpene resins include aromatic modified terpene resins, hydrogenated terpene resins, hydrogenated aromatic modified terpene resins, etc. Examples of modified terpene phenol resins include hydrogenated terpene phenol resins, etc. Examples of modified styrene resins include styrene acrylic resins, styrene maleic acid resins, etc. Examples of modified xylene resins include phenol modified xylene resins, alkylphenol modified xylene resins, phenol modified resol type xylene resins, polyol modified xylene resins, polyoxyethylene added xylene resins, etc.

[0247] As other thermosetting resins, epoxy resins can be mentioned, for example.

[0248] Examples of epoxy resins include bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, glycidylamine type resins, alicyclic epoxy resins, aminopropane type epoxy resins, biphenyl type epoxy resins, naphthalene type epoxy resins, anthracene type epoxy resins, triazine type epoxy resins, dicyclopentadiene type epoxy resins, triphenylmethane type epoxy resins, fluorene type epoxy resins, phenol aralkyl type epoxy resins, and novolac type epoxy resins.

[0249] Conventionally, in order to reduce flux residue, it has been proposed to reduce the rosin content in the flux. In a flux with a reduced rosin content, it becomes difficult to obtain rheological properties of the flux such as viscosity and thixotropic ratio of the flux.

[0250] The flux of the present embodiment described above can reduce flux residue and suppress heat collapse by containing the first solvent and the specific polyamide. The reason for obtaining this effect is not clear, but it is presumed as follows.

[0251] The specific polyamide having three or more amide bonds in the molecule is more likely to improve the ability to suppress heat collapse than monoamide and bisamide. The flux of this embodiment can suppress heat collapse even if it does not contain rosin.

[0252] Specific polyamides tend to improve the ability to suppress heat slump compared to monoamides and bisamides. However, flux containing specific polyamides tends to generate flux residues after reflow soldering.

[0253] Since the specific polyamide can easily improve the ability to suppress the slump when heated, the amount of addition required to obtain the specified ability to suppress the slump when heated can be reduced. In addition, in the flux of this embodiment, the first solvent is likely to remain after preheating and before the main heating, so it is easy to suppress the thixotropic agent, activator, etc. from drying up. In addition, in the flux of this embodiment, the first solvent is likely to volatilize during the main heating of the reflow soldering. Due to their synergistic effect, the flux of this embodiment, even if it contains a specific polyamide, can reduce the flux residue derived from the thixotropic agent, activator, first solvent, etc. by containing the first solvent.

[0254] (Solder Paste)

[0255] The solder paste of the second aspect contains solder alloy powder and the above-mentioned flux.

[0256] The solder alloy powder can be composed of powder of solder of Sn alone, or powder of Sn-Ag system, Sn-Cu system, Sn-Ag-Cu system, Sn-Bi system, Sn-In system, etc., or powder of solder alloy with Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. added to these alloys.

[0257] The solder alloy powder can also be composed of powder of a solder alloy formed by adding Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. to the Sn-Pb system or the Sn-Pb system.

[0258] The solder alloy powder is preferably a solder that does not contain Pb.

[0259] As the solder alloy powder, for example, a solder alloy powder having a melting temperature of 150 to 250° C. can be used.

[0260] Flux content:

[0261] In the solder paste, the content of the flux is preferably 5 to 30% by mass, more preferably 5 to 15% by mass, based on the total mass of the solder paste.

[0262] The solder paste of the present embodiment described above can reduce flux residue and suppress heat collapse.

[0263] (Method for preparing a conjugate)

[0264] The method for producing a bonded body according to the third aspect includes the step of obtaining the bonded body by soldering a component and a substrate, wherein the soldering is performed by reflowing in a reducing gas atmosphere using the solder paste according to the second aspect.

[0265] Hereinafter, one embodiment of the method for producing a joined body according to the third aspect will be described.

[0266] The method for producing a bonded structure according to the present embodiment is a method that includes a solder paste coating step, a component mounting step, and a reflow step in sequence.

[0267] In the solder paste applying step, the solder paste of the second embodiment is applied to the surface of the substrate.

[0268] Examples of the substrate include a printed wiring board and a wafer.

[0269] Examples of the method for applying the solder paste include a method of applying the solder paste by printing using a mask having openings, a method of discharging the solder paste using a dispenser or the like, and a method of transferring the solder paste using a probe or the like.

[0270] In the component mounting step, components are mounted on the surface of the substrate to which the solder paste is applied.

[0271] Examples of the component include a chip, an integrated circuit, a transistor, a diode, a resistor, and a capacitor.

[0272] The atmosphere of the reflow process is not particularly limited as long as the effects of the present invention can be achieved, and may be, for example, a nitrogen atmosphere or a reducing gas atmosphere.

[0273] The reducing gas atmosphere may be formed, for example, by volatilizing a reducing compound in a reflow furnace, or by supplying a reducing gas obtained by passing nitrogen through a liquid reducing compound into the reflow furnace. Formic acid is preferred as the reducing compound.

[0274] When the atmosphere of the reflow process is a reducing gas atmosphere, the amount of activator in the solder paste used may be reduced or the activator may not be contained, thereby further reducing the flux residue.

[0275] In the reflow process, the substrate after the components are mounted is heated in a reflow furnace at a temperature higher than the melting point of the solder powder contained in the solder paste (i.e., the peak temperature) (this is called the formal heating process). The heating temperature may be, for example, 5 to 30°C higher than the melting point of the solder powder. The heating time may be, for example, 10 seconds to 2 minutes.

[0276] The reflow process may include a preheating process before the main heating process.

[0277] The preheating step is to heat the substrate after mounting the components in a reflow furnace at a temperature lower than the melting point of the solder powder contained in the solder paste. The heating temperature may be, for example, 150 to 180° C. The heating time may be, for example, 30 seconds to 2 minutes.

[0278] In the preheating step, the interior of the reflow furnace may be in the above-mentioned nitrogen atmosphere or in a reducing gas atmosphere.

[0279] According to the method for producing a bonded body of the present embodiment described above, since flux residue can be reduced and heat collapse can be suppressed, the bonding strength of the resulting bonded body can be improved. In addition, the possibility of short circuits in the substrate can be reduced.

[0280] Example

[0281] Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to the following examples.

[0282] <Preparation of flux>

[0283] (Examples 1 to 23, Comparative Examples 1 to 4)

[0284] The fluxes of Examples and Comparative Examples were prepared according to the compositions shown in Tables 1 to 4.

[0285] The raw materials used are as follows.

[0286] Solvent:

[0287] First solvent:

[0288] Isobornyl cyclohexanol: boiling point 318°C, viscosity at 30°C above 10 Pa·s

[0289] Trimethylolpropane: melting point 60°C, boiling point 295°C

[0290] Secondary solvent:

[0291] Diethylene glycol monohexyl ether (relative dielectric constant 6.58, boiling point 259°C)

[0292] In the general formula (1), R of diethylene glycol monohexyl ether is 1 is ethylene, R 2 It is a straight-chain hexyl group, and m is 2.

[0293] Other solvents:

[0294] Ethylene glycol monophenyl ether (relative dielectric constant 6.01, boiling point 237°C)

[0295] Propylene glycol monophenyl ether (relative dielectric constant 4.47, boiling point 243°C)

[0296] Diethylene glycol mono-2-ethylhexyl ether (relative dielectric constant 5.04, boiling point 272°C)

[0297] Tripropylene glycol n-butyl ether (relative dielectric constant 4.48, boiling point 274°C)

[0298] Diethylene glycol monobutyl ether (relative dielectric constant 8.37, boiling point 231°C)

[0299] Isostearyl alcohol (relative dielectric constant 2.67, boiling point 304°C)

[0300] 2-Methylpentane-2,4-diol (relative dielectric constant 4.47, boiling point 197°C)

[0301] α-Terpineol (relative dielectric constant 3.04, boiling point 218°C)

[0302] Thixotropic agent:

[0303] Polyamide:

[0304] The polyamide used was obtained by the following method.

[0305] 12-Hydroxystearic acid and dodecanedioic acid were added, heated to about 100°C, and then hexamethylenediamine was added, heated to about 220°C, and maintained for 3 hours to obtain the polyamide of Preparation Example 1.

[0306] The moles of dodecanedioic acid used as raw materials are X, 12-hydroxystearic acid is Y, and hexamethylenediamine is Z. The molar numbers of the raw materials satisfy the relationship 2Z=2X+Y.

[0307] Other thixotropic agents:

[0308] Stearic acid amide, N,N'-methylene bis(stearic acid amide), hydrogenated castor oil

[0309] Active Agent:

[0310] Organic acid mixture (an organic acid mixture consisting of 2-methylzelaic acid, 4-(methoxycarbonyl)-2,4-dimethylundecanedioic acid, 4,6-di(methoxycarbonyl)-2,4,6-trimethyltridecanedioic acid and 8,9-di(methoxycarbonyl)-8,9-dimethylhexadecanedioic acid)

[0311] Diglycolic acid

[0312] The value of the boiling point of the compound used in the examples is a value obtained by measuring the temperature of the liquid when the saturated vapor pressure of the liquid of interest is equal to 1 atmosphere (ie, 1013 hPa).

[0313] Weight reduction rate:

[0314] The weight reduction rate of the solvent is measured as follows.

[0315] Using a differential thermal-thermogravimetric simultaneous measuring apparatus (manufactured by Hitachi High-Tech Scientific Co., Ltd., STA7200), 10 mg of the sample to be measured was placed in an aluminum pan, and heating was started, and the temperature was raised to a specific temperature at 10°C / min. Then, the weight loss rate was calculated by the following calculation formula based on the mass W0 of the sample before heating and the mass W1 of the sample when the sample reached the specific temperature.

[0316] Weight reduction rate (mass %) = 100 × (W0-W1) / W0

[0317] Weight loss rate when heated to 230℃

[0318] Isobornyl cyclohexanol: 81% by mass

[0319] Trimethylolpropane: 94 mass%

[0320] Weight loss rate when heated to 250℃

[0321] Isobornyl cyclohexanol: 99% by mass or more

[0322] Trimethylolpropane: 99% by mass or more

[0323] Relative dielectric constant:

[0324] The relative dielectric constant of the solvent was measured in accordance with JIS C2565 (1992) at a measurement frequency of 1 GHz.

[0325] Endothermic peak of polyamide

[0326] The temperature of the endothermic peak of the polyamide of Preparation Example 1 was measured by DSC (Differential Scanning Calorimetry).

[0327] As a more specific method for measuring the endothermic peak, the temperature of about 7 mg of the polyamide of Preparation Example 1 was raised from 30°C to 220°C under a nitrogen atmosphere with the heating rate set to 20°C / min. A DSC7020 (manufactured by Hitachi High-Tech Scientific) was used as a measuring instrument. The temperature of the peak top was defined as the temperature of the endothermic peak. The measurement results are shown in Figure 1 .

[0328] The peak top temperatures of all endothermic peaks of the obtained polyamide are 120° C. or higher and 200° C. or lower.

[0329] The ratio of heat absorption of polyamide

[0330] For the polyamide of Preparation Example 1, the ratio of the amount of heat absorbed at a certain temperature was calculated as follows.

[0331] The endothermic amount of polyamide was calculated from the peak area of ​​the DSC curve of polyamide.

[0332] Here, the "ratio of the amount of heat absorbed at a certain temperature" refers to the ratio of the amount of heat absorbed in the range of 50°C to a certain temperature to the total amount of heat absorbed in the range of 50°C to 200°C. Figure 2 .

[0333] <Preparation of Solder Paste>

[0334] The fluxes of Examples 1 to 22 and Comparative Examples 1 to 4 were mixed with the following solder alloy powder (1) to prepare solder pastes. In the prepared solder pastes, the fluxes were 10% by mass and the solder alloy powders were 90% by mass.

[0335] The flux of Example 23 and the following solder alloy powder (2) were mixed to prepare a solder paste. In the prepared solder paste, the flux accounted for 12.5% ​​by mass and the solder alloy powder accounted for 87.5% by mass.

[0336] The solder alloy powder (1) is a powder composed of a solder alloy containing 3 mass % Ag, 0.5 mass % Cu, and the balance Sn. The solidus temperature of the solder alloy is 217° C., and the liquidus temperature is 219° C. The size of the solder alloy powder (1) satisfies the size (particle size distribution) of symbol 4 in the classification of powder size in JIS Z3284-1:2014 (Table 2).

[0337] The size (particle size distribution) that satisfies mark 4 is:

[0338] The ratio of the major axis to the minor axis of the powder is 1.2 or less.

[0339] The length of the minor axis of the powder is 40 μm or less.

[0340] The content of the powder having a minor axis length exceeding 38 μm is 1% by mass or less relative to the total amount of the powder (100% by mass).

[0341] The content of the powder having a minor axis length of 20 μm or more and 38 μm or less is 80 mass % or more relative to the total amount of the powder (100 mass %).

[0342] The content of the powder having a minor axis length of less than 20 μm is 10% by mass or less relative to the total amount of the powder (100% by mass).

[0343] The solder alloy powder (2) is a powder composed of a solder alloy containing 5 mass % Sb and the balance Sn. The solidus temperature of the solder alloy is 240° C. and the liquidus temperature is 243° C. The size of the solder alloy powder (2) is the same as that of the solder alloy powder (1).

[0344] According to the evaluation methods described in <Evaluation> below, "Evaluation of flux residue amount", "Evaluation of heat slump suppression capability", "Evaluation of solder ball generation suppression capability", "Evaluation of viscosity", and "Evaluation of component assemblability" were performed. These evaluation results are shown in Tables 1 to 4.

[0345] <Evaluation>

[0346] 《Evaluation of the amount of residual flux》

[0347] Verification method:

[0348] Using a differential thermal-thermogravimetric simultaneous measuring apparatus (manufactured by Hitachi High-Technologies, Ltd., STA7200), 10 mg of the flux of each example was added to an aluminum pan, and heating was started, and the temperature was raised to 250° C. at a rate of 10° C. / min. Then, the residual rate was calculated by the following calculation formula based on the mass W0 of the target sample before heating and the mass W1 of the target sample when the target sample reached 250° C.

[0349] Residual rate (%) = 100 × W1 / W0

[0350] Judgment criteria:

[0351] A: The residual rate is less than 10%.

[0352] B: The residual rate is 10% or more.

[0353] The evaluation results showed that flux A was acceptable and flux B was unacceptable.

[0354] 《Evaluation of Heating Slump Suppression Capability》

[0355] Verification method:

[0356] The prepared solder paste was evaluated for heating collapse according to the method described in the "Heating collapse test" of JIS Z3284-3:2014. First, a test plate was obtained by printing the solder paste using a metal mask having pattern holes shown in I (hole size 3.0×0.7) in FIG. 6 of the "Printing collapse test". The obtained test plate was left to stand in a thermostatic chamber at 150°C for 3 minutes. The schematic diagram of the pattern of I is shown in FIG. Figure 3 .exist Figure 3 The numerical values ​​of 0.2 to 1.2 represent the distance between the pattern holes. The minimum distance at which all the printed solder pastes do not become one is evaluated for the heated test board.

[0357] <Evaluation of Solder Ball Generation Suppression Capability>

[0358] Verification method:

[0359] Using a metal mask, the prepared solder paste was printed on a printed circuit board with a pad pattern for mounting chip components in a pattern of φ1.6 mm and a thickness of 0.12 mm. Next, using an assembly machine (NPM-W2 manufactured by Panasonic Corporation), 30 3216 chip capacitors were mounted on the printed circuit board after printing. Next, it was verified whether solder balls (called chip edge balls or capillary balls) were generated around the chip components.

[0360] Judgment criteria:

[0361] A: No solder balls larger than 0.1 mm in diameter are generated around the chip capacitor.

[0362] B: Solder balls with a diameter of 0.1 mm or more were generated around the chip capacitor.

[0363] The evaluation results showed that flux A was acceptable and flux B was unacceptable.

[0364] "Sticky Reviews"

[0365] Verification method:

[0366] The adhesive force of the flux after storage was evaluated according to the evaluation method described in JIS Z3284-3 (2014) 4.5. As a measuring device, TACKINESS TESTER TK-1 (manufactured by Malcom) was used.

[0367] Using a metal mask, the solder paste of each embodiment is printed on an alumina plate to prepare four printed patterns with a diameter of 6.5 mm and a thickness of 0.2 mm. Next, the alumina plate printed with the solder paste is placed in a sealed container and allowed to stand in a temperature and humidity control room at 25°C and 50% humidity for 8 hours. Then, the printed pattern is placed under the probe of the viscosity tester, and the center of the pattern is aligned with the center of the probe. Next, the probe is lowered into the paste at a speed of 2.0 mm / s and pressurized at a constant pressure of 0.05±0.005 N. Next, within 0.2 seconds after pressurization, the probe is lifted at a speed of 10 mm / s. For the four printed patterns, the force when the probe is peeled off is measured, and the largest force is taken as the adhesion. In the table, the unit of adhesion is [N].

[0368] 《Evaluation of component assemblability》

[0369] Verification method:

[0370] Using a metal mask, the prepared solder paste was printed on a printed circuit board with a pad pattern for mounting chip components in a pattern of φ1.6 mm and a thickness of 0.12 mm. Next, the printed circuit board printed with the solder paste was placed in a sealed container and left to stand for 8 hours at 25°C and 50% humidity in a temperature and humidity control room. Next, an assembly machine (NPM-W2 manufactured by Panasonic Corporation) was used to mount 30 3216 chip capacitors on the printed printed circuit board.

[0371] Judgment criteria:

[0372] A: There are no capacitors that are displaced relative to or detached from the substrate.

[0373] B: The number of capacitors that were displaced from the substrate or fell off the substrate was one or more.

[0374] [Table 1]

[0375]

[0376] [Table 2]

[0377]

[0378] [Table 3]

[0379]

[0380] [Table 4]

[0381]

[0382] The evaluation result of the flux residue amount of Examples 1 to 23 containing the first solvent was A.

[0383] The evaluation results of the ability to suppress heat slump of the fluxes of Examples 1 to 23 containing polyamide were less than 0.5 mm, and the evaluation results of the ability to suppress the generation of solder balls were A.

[0384] The fluxes of Comparative Examples 1, 3 and 4 not containing polyamide had a heat slump suppression ability of 0.6 mm or more and a solder ball generation suppression ability of B as the evaluation result.

[0385] The flux of Comparative Example 2, in which the polyamide content was 2% by mass, had an evaluation result of 0.5 mm for the ability to suppress the formation of solder balls and a B for the ability to suppress the formation of solder balls.

[0386] The evaluation result of the heat slump suppression capability of the flux of Example 18, in which the mass ratio represented by polyamide / second solvent was less than 0.15, was 0.4 mm.

[0387] The evaluation result of the heat slump suppression ability of the fluxes of Examples 16 to 17, in which the mass ratio represented by polyamide / second solvent was 0.15 to 0.40, was 0.2 mm.

[0388] That is, it was confirmed that the heat collapse suppression capability can be more easily improved by setting the mass ratio represented by polyamide / second solvent to 0.15 to 0.40.

[0389] The evaluation result of the heat slump suppression ability of the flux of Example 19 containing isobornylcyclohexanol was 0.3 mm.

[0390] The evaluation result of the heat slump suppression capability of the flux of Example 22 containing trimethylolpropane was 0.4 mm.

[0391] That is, it was confirmed that the flux containing isobornylhexanol as the first solvent tends to further improve the ability to suppress thermal collapse.

[0392] The fluxes of Examples 1, 9 to 11, 14 to 23, and Comparative Examples 1 to 4 containing the second solvent had a viscosity evaluation result of 0.3 N or more, and a component assembly property evaluation result of A.

[0393] The fluxes of Examples 2 to 8 and 12 to 13 not containing the second solvent had a viscosity evaluation result of 0.1N and a component assembly property evaluation result of B.

[0394] That is, it was confirmed that the presence of the first solvent and the second solvent further increased the viscosity of the flux and further improved the assembly performance of the components.

[0395] The fluxes of Examples 14 to 18, 21, and 23 in which the solvent consisting of the first solvent and the second solvent was blended had a viscosity evaluation result of 0.6N.

[0396] That is, it was confirmed that the evaluation result of the viscosity is easily improved by setting the mass ratio represented by the second solvent / the first solvent to 0.1 to 1.0.

[0397] Industrial Applicability

[0398] According to the present invention, a flux and a solder paste capable of reducing flux residue and suppressing heat collapse can be provided. The flux is suitable for soldering without a step of cleaning flux residue.

Claims

1. A soldering flux comprising a first solvent and a thixotropic agent, The first solvent has a viscosity of 10 Pa·s or more at 30° C. or is solid at 30° C., The boiling point of the first solvent is above 200°C, The weight reduction rate of the first solvent when heated to 230° C. is less than 96% by mass. The thixotropic agent contains polyamide, and the polyamide is one or more selected from the group consisting of a condensate of an aliphatic carboxylic acid and an amine, and a condensate of an aliphatic carboxylic acid, a hydroxyl-containing aliphatic carboxylic acid, and an amine. The content of the first solvent is 30% by mass or more relative to the total mass of the soldering flux. The content of the polyamide exceeds 2 mass % based on the total mass of the soldering flux.

2. The soldering flux according to claim 1, wherein The soldering flux further contains a second solvent (but excluding the solvent belonging to the first solvent), The second solvent has a boiling point of 250° C. or higher and a relative dielectric constant of 6.0 or higher.

3. The soldering flux according to claim 2, wherein: The second solvent is a compound represented by the following general formula (1): [Chemical formula 1] In the formula, R 1 represents a hydrocarbon group having 2 to 4 carbon atoms, R 2 It represents a hydrocarbon group having 4 to 10 carbon atoms, and m is 1 to 3.

4. The soldering flux according to claim 2, wherein The mass ratio of the first solvent to the second solvent is 0.1 to 1.0 as represented by the mass ratio of the second solvent / the first solvent.

5. The soldering flux according to claim 2, wherein: The mass ratio of the polyamide to the second solvent is 0.15 to 0.4 as a mass ratio represented by polyamide / second solvent.

6. The soldering flux according to claim 1, wherein The aliphatic carboxylic acid contains dicarboxylic acid.

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

8. A method for preparing a joint body, comprising the step of obtaining the joint body by welding a component and a substrate, During the soldering, the solder paste according to claim 7 is used and reflow soldering is performed in a reducing gas atmosphere.

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