Preparation Methods of Flux, Solder Paste and Bonded Body

Abstract

The soldering 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°C or is a solid at 30°C, a boiling point of 200°C or more, and a weight reduction rate of less than 96% by mass when heated to 230°C. The thixotropic agent contains a polyamide, and the polyamide is one or more selected from condensates of aliphatic carboxylic acids and amines, and condensates of aliphatic carboxylic acids, hydroxy-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 soldering flux. The content of the polyamide exceeds 2% by mass relative to the total mass of the soldering flux.

Description

Technical Field

[0001] The present invention relates to a method for preparing a soldering flux, a solder paste, and a bonded body.

[0002] This application claims priority based on Japanese Patent Application No. 2022-118197 filed in Japan on July 25, 2022, and incorporates its content herein. Background Art

[0003] Generally, fixing a component to a substrate and electrically connecting the component to the substrate are performed by soldering. In soldering, a soldering flux, solder powder, and a solder paste in which the soldering flux and the solder powder are mixed are used.

[0004] The soldering flux has the effect of chemically removing metal oxides present on the metal surface of the bonding object to be soldered and in the solder, and enabling metal elements to move at the boundary between the two. Therefore, by using a soldering flux for soldering, an intermetallic compound is formed between the two, thereby obtaining a firm bond.

[0005] In soldering using a solder paste, first, the solder paste is printed on a substrate, a component is mounted, and the substrate on which the component is mounted is heated using a heating furnace called a reflow furnace. As a result, the solder powder contained in the solder paste melts, and the component is soldered to the substrate.

[0006] The soldering flux used in reflow soldering generally contains a resin component, a solvent, an activator, a thixotropic agent, etc. In order to make the rheological properties such as the viscosity and thixotropic ratio of the soldering flux appropriate, rosin is added as a resin component to the soldering flux. Rosin remains as a soldering flux residue after reflow soldering.

[0007] On the other hand, in Patent Document 1, a solder paste with reduced soldering flux residue by not containing rosin is proposed.

[0008] Prior Art Documents

[0009] Patent Documents

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

[0011] Problems to be Solved by the Invention

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

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

[0014] Means for Solving the Problems

[0015] The present invention includes the following methods.

[0016] [1] A soldering flux containing 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 a solid at 30°C, the boiling point of the first solvent is 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 contains polyamide, and the polyamide is one or more selected from condensates of aliphatic carboxylic acids and amines, and condensates of aliphatic carboxylic acids, hydroxy-containing aliphatic carboxylic acids and amines. The content of the first solvent is 30% by mass or more relative to the total mass of 100% by mass of the soldering flux, and the content of the polyamide is more than 2% by mass relative to the total mass of 100% by mass of the soldering flux.

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

[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] [In the formula, R 1 represents a hydrocarbon group having 2 to 4 carbon atoms. R 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 the mass ratio of the first solvent to the second solvent is 0.1 to 1.0 in terms of the mass ratio represented by 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 dicarboxylic acid.

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

[0026] [8]A method for preparing a bonded body, which includes a step of obtaining a bonded body by soldering a component to a substrate. When performing the soldering, the solder paste described in [7] is used, and reflow soldering is performed in a reducing gas atmosphere.

[0027] Effects of the present invention

[0028] According to the present invention, it is possible to provide a flux, a solder paste, and a method for preparing a bonded body that can reduce flux residues and suppress heating slump. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0030] Figure 2 It is a graph showing the relationship between the proportion of the heat absorption amount of the polyamide contained in the flux according to an embodiment of the present invention and the temperature.

[0031] Figure 3 It is a diagram schematically showing the pattern hole I in the evaluation of the heating slump suppression ability. DETAILED DESCRIPTION OF THE INVENTION

[0032] (Flux)

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

[0034] By containing a first solvent and a specific polyamide, the flux of the present embodiment can reduce flux residues and easily impart prescribed rheological properties to the flux.

[0035] Reflow soldering includes, for example, the steps listed below. First, the substrate on which the components are mounted is heated at 150 to 180 °C for 1 to 2 minutes (this is called preheating). Then, it is heated at a temperature from the liquidus temperature of the solder alloy to a temperature about 20 °C higher than the liquidus temperature (this is called the peak temperature) for about 1 minute (this is called main heating).

[0036] The flux of the present embodiment is difficult to volatilize during preheating. Therefore, before main heating after preheating, the first solvent easily remains. Thus, it is easy to suppress the drying of the thixotropic agent, the activator, etc. to become flux residues. Since the flux of the present embodiment is difficult to volatilize during preheating, it is easy to suppress the volatilization of the activator, etc. As a result, it is easy to maintain the action of the activator, etc. In other words, it is easy to improve the heat resistance of the flux.

[0037] Furthermore, in the formal heating of the reflow soldering, the first solvent in the soldering flux of the present embodiment is likely to volatilize at a temperature near the peak temperature. As a result, since the amount of the solvent remaining after the reflow soldering is reduced, it is easy to reduce the soldering flux residue.

[0038] In addition, the soldering flux of the present embodiment is likely to suppress heating slump by containing a specific polyamide. Since the specific polyamide is likely to improve the heating slump suppression ability, the addition amount necessary to obtain a specified heating slump suppression ability can be reduced. As a result, the soldering flux residue can be reduced.

[0039] <Solvent>

[0040] <<First Solvent>>

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

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

[0043] As a result, even when the soldering flux does not contain rosin, the soldering flux of the present embodiment can easily keep the rheological properties of the soldering flux at a specified level.

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

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

[0046] Here, the melting point is the temperature at which a solid melts into a liquid. The melting point values of the compounds in this specification are mainly the values described in "Kagaku Binran Kisohen Kaitei Dai 5 Han".

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

[0048] By making the boiling point of the first solvent be above the lower limit value, the first solvent is likely to remain after preheating and before formal heating. Therefore, it is easy to maintain the functions of the thixotropic agent, activator, etc. As a result, after preheating and before formal heating, it is easy to improve the heat resistance of the solder flux and to suppress the curing of the thixotropic agent, activator, etc. to become solder flux residues.

[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, and particularly preferably 330 °C or lower.

[0050] By making the boiling point of the first solvent be below the upper limit value, the solder flux is likely to volatilize during formal heating. Thus, after formal heating, it is easy to reduce the solder flux residues.

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

[0052] In this specification, the boiling point means the temperature of the target liquid when the saturated vapor pressure of the liquid is equal to 1 atmospheric pressure (i.e., 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 making the weight reduction rate within the above range, the first solvent is likely to remain after preheating and before formal heating. Therefore, it is easy to maintain the function of the activator, etc. As a result, after preheating and before formal heating, it is easy to improve the heat resistance of the solder flux and to suppress the curing of the thixotropic agent, activator, etc. to become solder flux residues.

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

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

[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 measurement device (manufactured by Hitachi High - Technologies Science Corporation, STA7200), place 10 mg of the test sample to be measured in an aluminum pan, start heating, and raise the temperature at a rate of 10 °C / min to a specific temperature. Then, based on the mass W0 of the test sample before heating and the mass W1 of the test sample when it reaches the specific temperature, calculate the weight reduction rate using the following calculation formula.

[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, still more preferably 98% by mass or more, and particularly preferably 99% by mass or more.

[0061] By making the weight reduction rate of the first solvent when heated to 250 °C within the above - mentioned range, the flux is likely to volatilize during reflow soldering. Thus, it is easier to reduce flux residues after reflow soldering.

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

[0063] The upper limit value 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, still more 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 can be used alone or in combination of two or more.

[0065] Examples of the first solvent include isobornyl cyclohexanol, trimethylolpropane, etc., and isobornyl cyclohexanol is preferred.

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

[0067] The content of the first solvent is preferably 95% by mass or less, more preferably 90% by mass or less, still more preferably 85% by mass or less, and particularly preferably 80% by mass or less based on the total mass (100% by 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 soldering flux. Additionally, the content of the first solvent is preferably 30% by mass or more and 86% by mass or more, more preferably 40% by mass or more and 86% by mass or less, relative to the total mass (100% by mass) of the soldering flux.

[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] One type of other solvent may be used alone, or two or more types may be used in combination.

[0073] Examples of other solvents include the following solvents. The numbers in parentheses indicate the boiling points of the solvents.

[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 alcohol solvents 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 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 ester solvents include bis(2-ethylhexyl) sebacate.

[0078] (Second solvent)

[0079] In addition to the first solvent, the soldering flux of this embodiment may further contain a second solvent.

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

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

[0082] The relative dielectric constant of the second solvent is preferably 6.0 or higher and 50 or lower, more preferably 6.0 or higher and 30 or lower, still more preferably 6.0 or higher and 20 or lower, even more preferably 6.0 or higher and 15 or lower, and particularly preferably 6.0 or higher and 9.0 or lower.

[0083] Here, the relative dielectric constant is measured with the measurement frequency set to 1 GHz based on JISC2565 (1992). Specifically, a transmissive circular TM 010 mode resonator is used. The sample is mounted at the center of the resonator so that it is aligned with the axis of the resonator. An external magnetic field is applied in the axial direction of the sample until no change in the measured value can be observed even when the magnetic field changes, and the resonance frequency f1 is measured. Except for not mounting the sample on the resonator, the frequency f0 is measured in the same procedure. 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] By using the first solvent and the second solvent in combination, the solder paste printed on the substrate is less likely to volatilize during storage. As a result, it is easy to suppress the decrease in the viscosity of the solder paste containing the soldering flux, and it is easy to improve the assemblability of components to 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. R2 represents a hydrocarbon group having 4 to 10 carbon atoms. m is 1 to 3.

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

[0092] Examples of the aliphatic hydrocarbon group include linear or branched aliphatic hydrocarbon groups, or aliphatic hydrocarbon groups having a ring structure in the molecule, etc. Preferred is a linear aliphatic hydrocarbon group.

[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 linear aliphatic hydrocarbon group in, preferably a linear alkylene group. Specifically, examples include methylene [-CH2-], ethylene [-(CH2)2-], trimethylene [-(CH2)3-], tetramethylene [-(CH2)4-], etc. Preferred is ethylene [-(CH2)2-].

[0095] As R 1 the branched aliphatic hydrocarbon group in, preferably a branched alkylene group. Specifically, examples include alkylmethylenes such as -CH(CH3)-, -CH2-CH(CH3)-, -CH(CH2CH3)-, -C(CH3)2-, -C(CH3)(CH2CH3); alkylethylenes such as -CH(CH3)CH2-, -CH(CH3)CH(CH3)-, -C(CH3)2CH2-, -CH(CH2CH3)CH2-; alkyltrimethylenes such as -CH(CH3)CH2CH2-, -CH2CH(CH3)CH2-, etc. Preferred is -CH2-CH(CH3)-.

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

[0097] More specifically, examples of the aliphatic hydrocarbon group include linear or branched aliphatic hydrocarbon groups, or aliphatic hydrocarbon groups having a ring structure in the molecule, etc.

[0098] R 2 The hydrocarbon group in preferably has 4 to 8 carbon atoms, more preferably 5 to 7 carbon atoms, and most preferably 6 carbon atoms.

[0099] As the compound represented by the general formula (1), diethylene glycol monohexyl ether is preferred.

[0100] In the general formula (1), for diethylene glycol monohexyl ether, R1 is ethylene, and R 2 is a linear hexyl group, and m is 2.

[0101] The content of the second solvent is preferably 60% by mass or less, more preferably 50% by mass or less, still more preferably 40% by mass or less, particularly preferably 30% by mass or less, and most preferably 25% by mass or less, based on the total mass (100% by mass) of the solder flux.

[0102] By making the content of the second solvent not more than the above upper limit value, it is easy to improve the heating slump inhibition ability and the solder ball generation inhibition ability.

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

[0104] By making the content of the second solvent not less than the above lower limit value, it is easy to improve the viscosity of the solder paste containing the solder flux and the assemblability of components to a substrate printed with the solder paste containing the solder flux.

[0105] The content of the second solvent is preferably 5% by mass or more and 60% by mass or less, more preferably 5% by mass or more and 50% by mass or less, still more preferably 10% by mass or more and 46% by mass or less, further more preferably 10% by mass or more and 40% by mass or less, particularly preferably 10% by mass or more and 30% by mass or less, and most preferably 10% by mass or more and 25% by mass or less, based on the total mass (100% by mass) of the solder flux.

[0106] In the solder flux of the present embodiment, the mass ratio of the first solvent to the second solvent, which is expressed as the mass ratio of the second solvent to the first solvent, i.e., the ratio of the total mass of the second solvent to the total mass of the first solvent, is preferably 0.1 to 1.0.

[0107] By making the mass ratio expressed as the second solvent / the first solvent within the above range, it is easy to improve the viscosity of the solder flux and the assemblability of components to a substrate printed with the solder paste containing the solder flux.

[0108] In all the solvents in the solder flux of the present embodiment, the total content of the first solvent and the second solvent is preferably 65% by mass or more and 100% by mass or less, more preferably 75% by mass or more and 100% by mass or less, still more preferably 85% by mass or more and 100% by mass or less, further more preferably 100% by mass, based on the total mass (100% by mass) of all the solvents.

[0109] By having the total content of the first solvent and the second solvent within the above range in all the solvents of the solder flux, it is easy to increase the viscosity of the solder flux and easy to improve the assemblability of components to a substrate printed with a solder paste containing the solder flux.

[0110] <Thixotropic agent>

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

[0112] <Polyamide>

[0113] In the present 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 relative to the total amount (100% by mass) of the solder flux.

[0115] The specific polyamide is one or more selected from "condensates of aliphatic carboxylic acids and amines" and "condensates of hydroxy-containing aliphatic carboxylic acids, aliphatic carboxylic acids and amines", and preferably "condensates of hydroxy-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] As the aliphatic carboxylic acid, for example, monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, etc. can be cited. 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, and more preferably linear.

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

[0120] As the number of carbon atoms of the aliphatic monocarboxylic acid, it is preferably 12 to 22, more preferably 14 to 22, and further preferably 16 to 22.

[0121] As the aliphatic monocarboxylic acid, for example, lauric acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, etc. can be cited. The aliphatic unit carboxylic acid is preferably palmitic acid or stearic acid.

[0122] As the number of carbon atoms of the aliphatic dicarboxylic acid, it is preferably 2 to 20, more preferably 6 to 16, and further preferably 8 to 14.

[0123] As the aliphatic dicarboxylic acid, for example, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, etc. may be mentioned. 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 still 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 hydroxy 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 hydroxy aliphatic carboxylic acid may be any of linear, branched or cyclic. The hydrocarbon group is preferably linear or branched, and more preferably linear.

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

[0128] As the number of carbon atoms of the hydroxy aliphatic carboxylic acid, it is preferably 10 to 25, and more preferably 15 to 21.

[0129] As the hydroxy aliphatic carboxylic acid, for example, hydroxypentadecanoic acid, hydroxyhexadecanoic acid, hydroxyheptadecanoic acid, hydroxyoctadecanoic acid (hydroxystearic acid), hydroxyeicosanoic acid, hydroxyheneicosanoic acid, etc. may be mentioned. The hydroxy aliphatic carboxylic acid is preferably hydroxystearic acid, and more preferably 12-hydroxystearic acid.

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

[0131] As the amine, for example, aliphatic amine, aromatic amine may be mentioned. The amine is preferably an aliphatic amine.

[0132] As the amine, for example, monoamine, diamine, triamine, tetraamine, etc. may be mentioned. 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, and more preferably linear. As the number of carbon atoms of the aliphatic amine, it is preferably 3 to 10, and more preferably 4 to 8.

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

[0135] Examples of the amine include ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 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, pyrimidine-2,4,5,6-tetramine, etc. The amine is preferably hexamethylenediamine.

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

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

[0138] The specific polyamide used in the soldering flux of this embodiment has one or two or more endothermic peaks in the temperature range of 120 °C or higher and 200 °C or lower.

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

[0140] When the number of endothermic peaks is two or more, the specific polyamide may be such that the endothermic peak with the lowest temperature is in the range of 120 °C or higher and 200 °C or lower, or the endothermic peak with the highest temperature is in the range of 120 °C or higher and 200 °C or lower, or all the endothermic peaks are in the range of 120 °C or higher and 200 °C or lower.

[0141] The temperature of the endothermic peak with the highest temperature is preferably 150 °C or higher and 200 °C or lower, more preferably 160 °C or higher and 200 °C or lower, further preferably 170 °C or higher and 200 °C or lower, and particularly preferably 180 °C or higher and 200 °C or lower.

[0142] In the measurement using DSC, with respect to the total heat absorption in the range of 50 °C or higher and 200 °C or lower, the proportion of the heat absorption of the specific polyamide in the range of 160 °C or higher and 200 °C or lower is preferably 30% or more, more preferably 40% or more, and further preferably 45% or more.

[0143] By making the proportion of the heat absorption amount in the range of 160 °C or higher and 200 °C or lower in the measurement of a specific polyamide using DSC be at least the lower limit value, heating slump during reflow soldering can be sufficiently suppressed. In particular, even when the preheating temperature increases, for example, when it is 190 °C or higher, and further when it is 200 °C or higher, heating slump can be suppressed.

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

[0145] In the measurement of a specific polyamide using DSC, the proportion of the heat absorption amount in the range of 50 °C or higher and 150 °C or lower with respect to the total heat absorption amount in the range of 50 °C or higher and 200 °C or lower is preferably 80% or less, more preferably 60% or less, and still more preferably 50% or less.

[0146] The lower limit value of the proportion of the heat absorption amount is not particularly limited as long as the effects of the present invention can be achieved. For example, it can be 10% or more, can be 20% or more, and can also be 30% or more.

[0147] The proportion of the heat absorption amount is preferably 10% or more and 80% or less, more preferably 10% or more and 60% or less, and still more preferably 10% or more and 50% or less. Alternatively, the proportion of the heat absorption amount is preferably 20% or more and 80% or less, more preferably 20% or more and 60% or less, and still more preferably 30% or more and 50% or less.

[0148] In the measurement of a specific polyamide using DSC, the proportion of the heat absorption amount in the range of 50 °C or higher and 180 °C or lower with respect to the total heat absorption amount in the range of 50 °C or higher and 200 °C or lower is preferably 95% or less, more preferably 90% or less, and still more preferably 85% or less.

[0149] The lower limit value of the proportion of the heat absorption amount is not particularly limited as long as the effects of the present invention can be achieved. For example, it can be 40% or more, can be 50% or more, and can also be 60% or more.

[0150] The proportion of the heat absorption amount is preferably 40% or more and 95% or less, more preferably 40% or more and 90% or less, and still more preferably 40% or more and 85% or less. Alternatively, the proportion of the heat absorption amount is preferably 50% or more and 95% or less, more preferably 50% or more and 90% or less, and still more preferably 60% or more and 85% or less.

[0151] From the viewpoint of further improving the heating slump suppression ability, the specific polyamide contained in the flux of the present embodiment is preferably a condensate of an aliphatic carboxylic acid, a hydroxy-containing aliphatic monocarboxylic acid, and an amine.

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

[0153] The specific polyamide contained in the soldering flux of this embodiment is further preferably a condensate of an aliphatic dicarboxylic acid having 8 to 14 carbon atoms, a hydroxy-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 one or more selected from sebacic acid and dodecanedioic acid, 12-hydroxy stearic 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-hydroxy stearic acid, and hexamethylenediamine.

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

[0157] Here, let the aliphatic dicarboxylic acid used as a raw material for the specific polyamide be X moles, the hydroxy-containing aliphatic monocarboxylic acid be Y moles, and the aliphatic diamine be Z moles.

[0158] Preferably, the total molar number of amino groups of the compounds contained in the raw materials is equal to the total molar number of carboxyl groups, or the total molar number of amino groups of the compounds contained in the raw materials is less than the total molar number of carboxyl groups. Specifically, it is preferable to satisfy 2Z ≤ 2X + Y.

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

[0160] The relationship of the molar ratio between 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% by mass with respect to the total amount (100% by mass) of the soldering flux, more preferably 3% by mass or more, further preferably 4% by mass or more, and particularly preferably 5% by mass or more.

[0162] By making the content of the specific polyamide be the above lower limit value or more, it is easy to improve the heating slump suppression ability and the solder ball generation suppression ability.

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

[0164] By making the content of the specific polyamide not more than the upper limit value, it is easier to reduce the flux residue.

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

[0166] In the flux, the mass ratio of the specific polyamide to the second solvent, in terms of the mass ratio represented by specific polyamide / second solvent, that is, the ratio of the total mass of the specific polyamide to the total mass of the second solvent, is preferably 0.08 to 0.4, and more preferably 0.15 to 0.4.

[0167] By making the mass ratio represented by specific polyamide / second solvent within the above range, it is easy to improve the heating slump inhibition ability and easy to improve the solder ball generation inhibition ability.

[0168] 《Other Thixotropic Agents》

[0169] In addition to polyamide, the thixotropic agent may contain other thixotropic agents.

[0170] As other thixotropic agents, for example, amide-based thixotropic agents, wax-based thixotropic agents, sorbitol-based thixotropic agents, etc. other than the above can be cited.

[0171] Other thixotropic agents can be used alone or in combination of two or more.

[0172] As amide-based thixotropic agents other than the above, for example, monoamides, diamides, and other polyamides can be cited.

[0173] As monoamides, for example, lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxy stearic acid amide, saturated fatty acid amide, oleic acid amide, erucic acid amide, unsaturated fatty acid amide, p-toluamide, p-toluenemethane amide, aromatic amide, hexamethylene hydroxy stearic acid amide, substituted amide, hydroxymethyl stearic acid amide, hydroxymethyl amide, fatty acid ester amide, etc. can be cited.

[0174] Examples of the bisamide include methylene bisstearamide, ethylene bislauramide, ethylene bis(hydroxy fatty acid (fatty acid having 6 to 24 carbon atoms)) amide, ethylene bisstearamide, ethylene bis(hydroxystearic acid) amide, saturated fatty acid bisamide, methylene bisoleamide, unsaturated fatty acid bisamide, isophthalic acid bisstearamide, aromatic bisamide, and the like.

[0175] Examples of other polyamides include saturated fatty acid polyamide, unsaturated fatty acid polyamide, aromatic polyamide, 1,2,3 - propane tricarboxylic acid tris(2 - methylcyclohexylamide), cyclic amide oligomer, acyclic amide oligomer, and the like.

[0176] Examples of the cyclic amide oligomer include an amide oligomer obtained by condensation polymerization of a dicarboxylic acid and a diamine into a cyclic form, an amide oligomer obtained by condensation polymerization of a tricarboxylic acid and a diamine into a cyclic form, an amide oligomer obtained by condensation polymerization of a dicarboxylic acid and a triamine into a cyclic form, an amide oligomer obtained by condensation polymerization of a tricarboxylic acid and a triamine into a cyclic form, an amide oligomer obtained by condensation polymerization of a dicarboxylic acid and a tricarboxylic acid with a diamine into a cyclic form, an amide oligomer obtained by condensation polymerization of a dicarboxylic acid and a tricarboxylic acid with a triamine into a cyclic form, an amide oligomer obtained by condensation polymerization of a dicarboxylic acid with a diamine and a triamine into a cyclic form, an amide oligomer obtained by condensation polymerization of a tricarboxylic acid with a diamine and a triamine into a cyclic form, and an amide oligomer obtained by condensation polymerization of a dicarboxylic acid and a tricarboxylic acid with a diamine and a triamine into a cyclic form.

[0177] In addition, examples of the acyclic amide oligomer include a case where a mono - carboxylic acid is condensed with a diamine and / or a triamine into an acyclic form to obtain an amide oligomer, a case where a dicarboxylic acid and / or a tricarboxylic acid is condensed with a mono - amine into an acyclic form to obtain an amide oligomer, and the like. When the amide oligomer contains a mono - carboxylic acid or a mono - amine, the mono - carboxylic acid and the mono - amine function as terminal molecules and become an acyclic amide oligomer with a reduced molecular weight. In addition, in the case of an amide compound obtained by condensation polymerization of a dicarboxylic acid and / or a tricarboxylic acid with a diamine and / or a triamine into an acyclic form, the acyclic amide oligomer becomes an acyclic high - molecular amide polymer. In addition, the acyclic amide oligomer also includes an amide oligomer obtained by condensation of a mono - carboxylic acid and a mono - amine into an acyclic form.

[0178] Examples of the wax - based thixotropic agent include ester compounds, and specifically, hydrogenated castor oil and the like can be mentioned.

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

[0180] <Other Components>

[0181] The soldering flux of the present embodiment may contain other components as needed 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 passivators, antioxidants, silane coupling agents, colorants, and the like.

[0183] 《Activator》

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

[0185] [Organic Acid]

[0186] Examples of organic acids include carboxylic acids and organic sulfonic acids. Examples of carboxylic acids include aliphatic carboxylic acids and aromatic carboxylic acids. Examples of aliphatic carboxylic acids include aliphatic monocarboxylic acids and aliphatic dicarboxylic acids.

[0187] Examples of aliphatic monocarboxylic acids include caproic 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, cyclopenteneundecanoic acid, heptadecanoic acid, isostearic acid, elaidic acid, petroselinic acid, stearatetraenoic acid, eleostearic acid, tariric acid,

[0188] 11-octadecenoic 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 aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, icosanedioic acid, tartaric acid, 2,4-diethylglutaric acid, diglycolic acid, 2-methylnonanedioic acid, 4-(methoxycarbonyl)-2,4-dimethylundecanedioic acid, 4,6-bis(methoxycarbonyl)-2,4,6-trimethyltridecanedioic acid, 8,9-bis(methoxycarbonyl)-8,9-dimethylhexadecanedioic acid, etc.

[0190] Examples of aromatic carboxylic acids include salicylic acid, dibutylaniline diglycolic acid, terephthalic acid, 4-hydroxyphenylacetic acid, phenylsuccinic acid, phthalic acid, benzoic acid, 2,3-dihydroxybenzoic acid, 2-quinolinecarboxylic acid, 3-hydroxybenzoic acid, p-anisic acid, etc.

[0191] In addition, examples of carboxylic acids include tris(2-carboxyethyl) isocyanurate, 1,3-cyclohexanedicarboxylic acid, etc.

[0192] In addition, as the carboxylic acid, a compound represented by the following general formula (c1) can be cited.

[0193] R 11 -COOH·(c1)

[0194] [In the formula, R 11 represents a linear hydrocarbon group having 2 to 15 carbon atoms, an alicyclic hydrocarbon group having 3 to 15 carbon atoms, or an aromatic group. Among them, R 11 has a hydroxyl group.]

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

[0196] The linear hydrocarbon group and the alicyclic hydrocarbon group can be saturated hydrocarbon groups or unsaturated hydrocarbon groups, and are preferably saturated hydrocarbon groups.

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

[0198] As the linear hydrocarbon group, for example, 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, neohexyl, etc. can be cited.

[0199] The number of carbon atoms of the alicyclic hydrocarbon group is preferably 3 to 12, more preferably 4 to 12, and further preferably 4 to 8.

[0200] As the alicyclic hydrocarbon group, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, cycloundecyl, etc. can be cited.

[0201] R 11 The aromatic group in is a group having at least 1 aromatic ring. For example, aromatic hydrocarbon rings such as benzene, naphthalene, anthracene, and phenanthrene, aromatic heterocycles in which a part of the carbon atoms constituting the aromatic hydrocarbon ring is substituted by a heteroatom, condensed rings formed by condensation of an aromatic hydrocarbon ring and an aromatic heterocycle, etc. can be cited.

[0202] R 11 When the aromatic group in has a substituent, as the substituent, 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, etc. can be cited, and a carboxyl group or a hydroxyl group is preferred.

[0203] As the organic acid represented by the above general formula (c1), hydroxycarboxylic acid can be cited.

[0204] As hydroxycarboxylic acids, for example, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butyric acid, citric acid, isocitric acid, malic acid, tartaric acid, etc. may be mentioned, and 2,2-bis(hydroxymethyl)propionic acid is preferred.

[0205] In addition, as carboxylic acids, dimer acid, trimer acid, hydrogenated dimer acid which is a hydride of hydrogenated dimer acid, hydrogenated trimer acid which is a hydride of hydrogenated trimer acid, etc. may be mentioned.

[0206] As dimer acid and trimer acid, for example, dimer acid which is a reaction product of oleic acid and linoleic acid, trimer acid which is a reaction product of oleic acid and linoleic acid, dimer acid which is a reaction product of acrylic acid, trimer acid which is a reaction product of acrylic acid, dimer acid which is a reaction product of methacrylic acid, trimer acid which is a reaction product of methacrylic acid, dimer acid which is a reaction product of acrylic acid and methacrylic acid, trimer acid which is a reaction product of acrylic acid and methacrylic acid, dimer acid which is a reaction product of oleic acid, trimer acid which is a reaction product of oleic acid, dimer acid which is a reaction product of linoleic acid, trimer acid which is a reaction product of linoleic acid, dimer acid which is a reaction product of linolenic acid, trimer acid which is a reaction product of linolenic acid, dimer acid which is a reaction product of acrylic acid and oleic acid, trimer acid which is a reaction product of acrylic acid and oleic acid, dimer acid which is a reaction product of acrylic acid and linoleic 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 linolenic 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 oleic 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 hydride of each of the above dimer acids, hydrogenated trimer acid which is a hydride of each of the above trimer acids, etc. may be mentioned.

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

[0208] In addition, as carboxylic acids, compounds represented by the following general formula (a1) may be mentioned.

[0209] [Chemical formula 3]

[0210]

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

[0212] As the hydrocarbon group in R a1 and R a2 and R a3 and R a4 examples thereof include a linear 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, etc.

[0213] The linear hydrocarbon group may be linear or branched. The linear hydrocarbon group is 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 the monocyclic alicyclic hydrocarbon group, a group formed by removing one or more hydrogen atoms from a monocycloalkane is preferred. As the polycyclic alicyclic hydrocarbon group, a group formed by removing one or more hydrogen atoms from a polycycloalkane is preferred.

[0215] As the hydrocarbon group in R a1 and R a2 and R a3 and R a4 the substituents which the hydrocarbon group may have include an amino group, a hydroxyl group, a carboxyl group, an acyl group, an alkoxy group, a carbonyl group, a halogen atom, etc.

[0216] As the hydrocarbon group, a linear hydrocarbon group having 1 to 5 carbon atoms which may have a substituent or a carboxyl group is preferred. As the linear hydrocarbon group, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, tert-pentyl, neopentyl, etc. may be mentioned. As the hydrocarbon group, a carboxyl group is preferred.

[0217] As the compound represented by the above general formula (a1), for example, picolinic acid, pyridine dicarboxylic acid, 3-hydroxypicolinic acid may be mentioned.

[0218] Picolinic acid is a compound in which R a1 and R a2 and R a3 and R a4 in the above general formula (a1) are hydrogen atoms.

[0219] 3-Hydroxypicolinic acid is a compound in which R a1 in the above general formula (a1) is a hydroxyl group and R a2 and R a3 and R a4 in the above general formula (a1) are hydrogen atoms.

[0220] As organic sulfonic acids, for example, aliphatic sulfonic acids, aromatic sulfonic acids, etc. can be cited. As aliphatic sulfonic acids, for example, alkane sulfonic acids, alkanol sulfonic acids, etc. can be cited.

[0221] As alkane sulfonic acids, for example, methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, 2-propanesulfonic acid, 1-butanesulfonic acid, 2-butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid, decanesulfonic acid, dodecanesulfonic acid, etc. can be cited.

[0222] As alkanol sulfonic acids, for example, 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, etc. can be cited.

[0223] As aromatic sulfonic acids, for example, 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, etc. can be cited.

[0224] The organic acid can 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] As the organic acid, an aliphatic dicarboxylic acid is preferred, and it preferably contains one or more selected from glycolic acid, 2-methylnonanedioic acid, 4-(methoxycarbonyl)-2,4-dimethylundecanedioic acid, 4,6-bis(methoxycarbonyl)-2,4,6-trimethyltridecanedioic acid, and 8,9-bis(methoxycarbonyl)-8,9-dimethyhexadecanedioic acid, and more preferably contains one or more selected from glycolic acid and an organic acid mixture composed of 2-methylnonanedioic acid, 4-(methoxycarbonyl)-2,4-dimethylundecanedioic acid, 4,6-bis(methoxycarbonyl)-2,4,6-trimethyltridecanedioic acid, and 8,9-bis(methoxycarbonyl)-8,9-dimethyhexadecanedioic acid.

[0227] [Amine]

[0228] As amines, for example, azoles, guanidines, amino alcohols, alkylamine compounds, amine polyoxyalkylene adducts, etc. can be cited.

[0229] As azoles, for example, 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-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-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-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]diethanol, 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-phenyltetrazole, etc.

[0230] As guanidines, for example, 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylguanidine, 1,3-di-o-isopropylphenylguanidine, 1,3-di-o-isopropylphenyl-2-propionylguanidine, etc. can be cited.

[0231] As amino alcohols, for example, 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, tris(2-hydroxypropyl)amine, etc. can be cited.

[0232] As alkylamine compounds, for example, ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, cetylamine, stearylamine, etc. can be cited.

[0233] As amine polyalkylene oxide adducts, for example, terminal diamine polyalkylene glycols, aliphatic amine polyalkylene oxide adducts, aromatic amine polyalkylene oxide adducts, polyamine polyalkylene oxide adducts, etc. can be cited.

[0234] As alkylene oxides added to amine polyalkylene oxide adducts, for example, ethylene oxide, propylene oxide, butylene oxide, etc. can be cited.

[0235] Terminal diamine polyalkylene glycol is a compound in which the two terminals of polyalkylene glycol are amidated.

[0236] As terminal diamine polyalkylene glycols, for example, terminal diamine polyethylene glycol, terminal diamine polypropylene glycol, terminal diamine polyethylene glycol-polypropylene glycol copolymer, etc. can be cited.

[0237] As terminal diamine polyethylene glycol-polypropylene glycol copolymers, for example, polyethylene glycol-polypropylene glycol copolymer bis(2-aminopropyl) ether, polyethylene glycol-polypropylene glycol copolymer bis(2-aminoethyl) ether can be cited.

[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 an amine. Examples of the amine include ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, hexamethylenediamine, diethylenetriamine, laurylamine, stearylamine, oleylamine, tallowamine, cured tallowamine, tallow propylenediamine, 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, pyrimidine-2,4,5,6-tetraamine, etc.

[0239] The amine can be used alone or in combination of two or more.

[0240] The flux of this embodiment preferably does not contain a resin component. By not containing a resin component, it is easy to reduce the amount of flux residue.

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

[0242] In this specification, "rosin" includes natural resins mainly composed of rosin acid and containing a mixture of rosin acid and its isomers, and resins obtained by chemically modifying natural resins (sometimes called rosin derivatives).

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

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

[0245] Examples of resins other than rosin include terpene resin, modified terpene resin, terpene phenol resin, modified terpene phenol resin, styrene resin, modified styrene resin, xylene resin, modified xylene resin, acrylic resin, polyethylene resin, acrylic-polyethylene copolymer resin, other thermosetting resins, etc.

[0246] Examples of the modified terpene resin include aromatic modified terpene resin, hydrogenated terpene resin, hydrogenated aromatic modified terpene resin, etc. Examples of the modified terpene phenol resin include hydrogenated terpene phenol resin, etc. Examples of the modified styrene resin include styrene acrylic resin, styrene maleic resin, etc. Examples of the modified xylene resin include phenol modified xylene resin, alkylphenol modified xylene resin, phenol modified resol type xylene resin, polyol modified xylene resin, polyethylene oxide added xylene resin, etc.

[0247] Examples of other thermosetting resins include, for example, epoxy resins.

[0248] Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, glycidylamine type resin, alicyclic epoxy resin, aminopropane type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, anthracene type epoxy resin, triazine type epoxy resin, dicyclopentadiene type epoxy resin, triphenylmethane type epoxy resin, fluorene type epoxy resin, phenol aralkyl type epoxy resin, novolak type epoxy resin, etc.

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

[0250] The flux of the present embodiment described above can reduce the flux residue and can suppress the heating slump by containing the first solvent and a specific polyamide. Although the reason for obtaining this effect is not clear, it is speculated as follows.

[0251] A specific polyamide having three or more amide bonds in the molecule is more likely to improve the heating slump inhibition ability compared with monoamide and diamide. The flux of the present embodiment can suppress the heating slump even without rosin.

[0252] A specific polyamide is more likely to improve the heating slump inhibition ability compared with monoamide and diamide. However, the flux containing the specific polyamide usually tends to generate flux residue after reflow soldering.

[0253] Specific polyamides can reduce the addition amount necessary to obtain a specified heat slump suppression ability because they can easily improve the heat slump suppression ability. In addition, in the solder paste of the present embodiment, the first solvent easily remains after preheating and before formal heating, so it is easy to suppress the drying and solidification of thixotropic agents, activators, etc. Further, in the solder paste of the present embodiment, the first solvent easily volatilizes during the formal heating of reflow soldering. Through their synergistic effects, the solder paste of the present embodiment can reduce the solder paste residues derived from thixotropic agents, activators, the first solvent, etc. even when containing a specific polyamide by containing the first solvent.

[0254] (Solder paste)

[0255] The solder paste of the second embodiment contains solder alloy powder and the above-described solder paste.

[0256] The solder alloy powder may be composed of powder of solder of Sn monomer, or powders of Sn-Ag-based, Sn-Cu-based, Sn-Ag-Cu-based, Sn-Bi-based, Sn-In-based, etc., or powders of solder alloys in which Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. are added to these alloys.

[0257] The solder alloy powder may also be composed of powders of solder alloys obtained by adding Sb, Bi, In, Cu, Zn, As, Ag, Cd, Fe, Ni, Co, Au, Ge, P, etc. to Sn-Pb-based or Sn-Pb-based alloys.

[0258] The solder alloy powder is preferably a Pb-free solder.

[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] Content of the solder paste:

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

[0262] The solder paste of the present embodiment described above can reduce the solder paste residues and can suppress heat slump.

[0263] (Method for preparing a bonded body)

[0264] The method for preparing a bonded body of the third embodiment includes a step of obtaining a bonded body by soldering a component and a substrate. During the soldering, the solder paste of the second embodiment is used and reflow soldering is performed in a reducing gas atmosphere.

[0265] Hereinafter, an embodiment of the method for preparing a bonded body of the third embodiment will be described.

[0266] The method for preparing the bonded body of the present embodiment is a method that sequentially includes a solder paste coating process, a component mounting process, and a reflow soldering process.

[0267] In the solder paste coating process, the solder paste of the second method is coated on the surface of the substrate.

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

[0269] Examples of the method for coating the solder paste include a method of coating the solder paste using a mask printing with an opening, a method of discharging the solder paste using a dispenser, a method of transferring the solder paste using a probe, and the like.

[0270] In the component mounting process, components are mounted on the surface of the substrate coated with the solder paste.

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

[0272] The atmosphere of the reflow soldering process is not particularly limited as long as it can achieve the effects of the present invention. For example, it can be a nitrogen atmosphere or a reducing gas atmosphere.

[0273] The reducing gas atmosphere can be formed, for example, by volatilizing a reducing compound in a reflow furnace, or can be formed by supplying a reducing gas obtained by passing nitrogen through a liquid reducing compound to the reflow furnace. As the reducing compound, formic acid is preferred.

[0274] When the atmosphere of the reflow soldering process is a reducing gas atmosphere, the amount of the active agent in the solder paste used can be reduced, or the solder paste can be free of the active agent. Thereby, the amount of the flux residue can be further reduced.

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

[0276] The reflow soldering process may also have a preheating process before the formal heating process.

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

[0278] In the preheating process, the inside of the reflow furnace may be the above nitrogen atmosphere or a reducing gas atmosphere.

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

[0280] Examples

[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 the 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 10 Pa·s or more

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

[0290] Second 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 1 is an ethylene group, R 2 is a linear 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] Isooctadecanol (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 uses a substance obtained by the following method.

[0305] Add 12-hydroxy stearic acid and dodecanedioic acid, heat to about 100 °C, then add hexamethylenediamine, heat to about 220 °C, and hold for 3 hours to obtain the polyamide of Preparation Example 1.

[0306] The dodecanedioic acid used as a raw material is X moles, 12-hydroxy stearic acid is Y moles, and hexamethylenediamine is Z moles. The molar amounts of the raw materials satisfy the relationship 2Z = 2X + Y.

[0307] Other thixotropic agents:

[0308] Stearamide, N,N'-methylenebis(stearamide), hydrogenated castor oil

[0309] Activator:

[0310] Organic acid mixture (an organic acid mixture composed of 2-methylnonanedioic acid, 4-(methoxycarbonyl)-2,4-dimethylundecanedioic acid, 4,6-bis(methoxycarbonyl)-2,4,6-trimethyltridecanedioic acid, and 8,9-bis(methoxycarbonyl)-8,9-dimethylhexadecanedioic acid)

[0311] Diglycolic acid

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

[0313] Weight loss rate:

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

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

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

[0317] Weight loss rate when heated to 230 °C

[0318] Isobornyl cyclohexanol: 81 mass %

[0319] Trimethylolpropane: 94 mass %

[0320] Weight loss rate when heated to 250 °C

[0321] Isobornyl cyclohexanol: 99 mass % or more

[0322] Trimethylolpropane: 99 mass % or more

[0323] Relative dielectric constant:

[0324] The relative dielectric constant of the solvent was measured with the measurement frequency set to 1 GHz based on JISC2565 (1992).

[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, in a nitrogen atmosphere, the heating rate was set to 20 °C / min, and about 7 mg of the polyamide of Preparation Example 1 was heated from 30 °C to 220 °C for measurement. As the measurement instrument, DSC7020 (manufactured by Hitachi High-Tech Science) was used. The temperature at the peak top was defined as the temperature of the endothermic peak. The measurement results are shown in Figure 1 .

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

[0329] Proportion of the heat absorption amount of polyamide

[0330] For the polyamide of Preparation Example 1, the proportion of the heat absorption amount at a specific temperature was calculated as follows.

[0331] The heat absorption amount of the polyamide is calculated from the peak area of the DSC curve of the polyamide.

[0332] Herein, the "proportion of the heat absorption amount at a specific temperature" means the ratio of the heat absorption amount in the range above 50°C and below the specific temperature to the total heat absorption amount in the range above 50°C and below 200°C. The results are shown in Figure 2 .

[0333] <Preparation of Solder Paste>

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

[0335] The soldering flux of Example 23 was mixed with the following solder alloy powder (2) to prepare solder paste. In the prepared solder paste, the soldering flux was 12.5% by mass and the solder alloy powder was 87.5% by mass.

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

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

[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] With respect to the total amount of the powder (100% by mass), the content of the powder with the length of the minor axis exceeding 38 μm is 1% by mass or less.

[0341] With respect to the total amount of the powder (100% by mass), the content of the powder with the length of the minor axis being 20 μm or more and 38 μm or less is 80% by mass or more.

[0342] With respect to the total amount of the powder (100% by mass), the content of the powder with the length of the minor axis less than 20 μm is 10% by mass or less.

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

[0344] According to the evaluation methods described in the following <Evaluation>, evaluations of "Evaluation of the amount of flux residue", "Evaluation of the ability to suppress heating slump", "Evaluation of the ability to suppress solder ball generation", "Evaluation of viscosity", and "Evaluation of component assemblability" were conducted. The results of these evaluations are shown in Tables 1 to 4.

[0345] <Evaluation>

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

[0347] Verification method:

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

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

[0350] Judgment criterion:

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

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

[0353] Regarding the evaluation result, the flux with A is qualified, and the flux with B is unqualified.

[0354] 《Evaluation of the ability to suppress heating slump》

[0355] Verification method:

[0356] For the prepared solder paste, the heating slump was evaluated according to the method described in the "Slump test during heating" of JIS Z3284-3:2014. First, a test board was obtained by printing the solder paste using a metal mask configured with the pattern holes shown in I (hole size 3.0 × 0.7) in Figure 6 of the "Slump test during printing". The obtained test board was left standing in a constant temperature bath at 150 °C for 3 minutes. The schematic diagram of the pattern of the above I is shown in Figure 3 . In Figure 3 , the numerical values from 0.2 to 1.2 represent the distance between the pattern holes. For the heated test board, the minimum interval at which the printed solder paste does not all become integrated was evaluated.

[0357] <Evaluation of the ability to suppress solder ball generation>

[0358] Verification method:

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

[0360] Judgment criteria:

[0361] A: Solder balls of φ0.1 mm or more are not generated around the chip capacitor.

[0362] B: Solder balls of φ0.1 mm or more are generated around the chip capacitor.

[0363] The evaluation result is that the flux of A is qualified and the flux of B is unqualified.

[0364] "Evaluation of Tackiness"

[0365] Verification method:

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

[0367] Using a metal mask, the solder paste of each example is printed on an alumina plate to prepare 4 printed patterns of φ6.5 mm and a thickness of 0.2 mm. Next, the alumina plate printed with the solder paste is placed in a sealed container and left standing for 8 hours at 25°C and a humidity of 50% in a temperature and humidity control chamber. Then, the printed pattern is placed under the probe of the tackiness 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 pressed with a constant pressing force of 0.05 ± 0.005 N. Then, within 0.2 seconds after pressing, the probe is lifted at a speed of 10 mm / s. For the 4 printed patterns, the force when the probe is peeled off is measured, and the maximum force among them is taken as the adhesive strength. In the table, the unit of the adhesive strength is [N].

[0368] "Evaluation of Assembly Property of Components"

[0369] Verification method:

[0370] Using a metal mask, a pattern of φ1.6 mm in diameter and 0.12 mm in thickness is printed on a printed circuit board having a pad pattern for mounting chip components with the modulated solder paste. Next, the printed circuit board printed with the solder paste is placed in a sealed container and left standing for 8 hours at 25 °C and 50% humidity in a temperature and humidity control chamber. Next, 30 3216 chip capacitors are mounted on the printed circuit board after printing using a mounter (manufactured by Panasonic Corporation, NPM-W2).

[0371] Judgment criteria:

[0372] A: Capacitors that are not offset from the substrate or detached from the substrate.

[0373] B: The number of capacitors that are offset from the substrate or detached from the substrate is 1 or more.

[0374] [Table 1]

[0375]

[0376] [Table 2]

[0377]

[0378] [Table 3]

[0379]

[0380] [Table 4]

[0381]

[0382] For the soldering fluxes of Examples 1 to 23 containing the first solvent, the evaluation result of the amount of flux residue is A.

[0383] For the soldering fluxes of Examples 1 to 23 containing polyamide, the evaluation result of the heating slump suppression ability is less than 0.5 mm, and the evaluation result of the solder ball generation suppression ability is A.

[0384] For the soldering fluxes of Comparative Examples 1, 3 to 4 that do not contain polyamide, the evaluation result of the heating slump suppression ability is 0.6 mm or more, and the evaluation result of the solder ball generation suppression ability is B.

[0385] For the soldering flux of Comparative Example 2 with a polyamide content of 2% by mass, the evaluation result of the heating slump suppression ability is 0.5 mm, and the evaluation result of the solder ball generation suppression ability is B.

[0386] For the soldering flux of Example 18 with a mass ratio of polyamide / second solvent less than 0.15, the evaluation result of the heating slump suppression ability is 0.4 mm.

[0387] For the soldering fluxes of Examples 16 to 17 where the mass ratio represented by polyamide / second solvent is 0.15 to 0.40, the evaluation result of the heating slump inhibition ability is 0.2 mm.

[0388] That is, it can be confirmed that by making the mass ratio represented by polyamide / second solvent be 0.15 to 0.40, it is easier to improve the heating slump inhibition ability.

[0389] For the soldering flux of Example 19 containing isobornyl cyclohexanol, the evaluation result of the heating slump inhibition ability is 0.3 mm.

[0390] For the soldering flux of Example 22 containing trimethylolpropane, the evaluation result of the heating slump inhibition ability is 0.4 mm.

[0391] That is, it can be confirmed that the soldering flux containing isobornyl hexanol as the first solvent is liable to further improve the heating slump inhibition ability.

[0392] For the soldering fluxes of Examples 1, 9 to 11, 14 to 23 and Comparative Examples 1 to 4 containing the second solvent, the evaluation result of the viscosity is 0.3 N or more, and the evaluation result of the assembly property of the components is A.

[0393] For the soldering fluxes of Examples 2 to 8, 12 to 13 not containing the second solvent, the evaluation result of the viscosity is 0.1 N, and the evaluation result of the assembly property of the components is B.

[0394] That is, it can be confirmed that by the co - existence of the first solvent and the second solvent, the viscosity of the soldering flux is further improved, and the assembly property of the components is further improved.

[0395] For the soldering fluxes of Examples 14 to 18, 21 and 23 formulated with the solvent composed of the first solvent and the second solvent, the evaluation result of the viscosity is 0.6 N.

[0396] That is, it can be confirmed that by making the mass ratio represented by the second solvent / first solvent be 0.1 to 1.0, it is easy to further improve the evaluation result of the viscosity.

[0397] Industrial applicability

[0398] According to the present invention, it is possible to provide a soldering flux and a solder paste that can reduce the soldering flux residue and can inhibit heating slump. This soldering flux is suitable for soldering in a process where there is no process for cleaning the soldering flux residue.

Claims

1. A soldering flux containing one or more selected from isobornyl cyclohexanol and trimethylolpropane, a compound represented by the following general formula (1) having a boiling point of 250 °C or higher and a relative dielectric constant of 6.0 or higher, and a thixotropic agent, In the formula, R 1 represents a hydrocarbon group having 2 to 4 carbon atoms, and R 2 represents a hydrocarbon group having 4 to 10 carbon atoms, and m is 1 to 3. The soldering flux does not contain a resin component, The thixotropic agent contains a polyamide, which is a condensate of an aliphatic carboxylic acid, a hydroxy-containing aliphatic carboxylic acid, and an amine, The content of one or more selected from isobornyl cyclohexanol and trimethylolpropane is 30% by mass or more based on 100% by mass of the total mass of the soldering flux, The content of the polyamide is more than 2% by mass based on 100% by mass of the total mass of the soldering flux.

2. The soldering flux according to claim 1, wherein, The mass ratio of the first solvent, which is one or more selected from isobornyl cyclohexanol and trimethylolpropane, to the second solvent, which is the compound represented by the above general formula (1) having a boiling point of 250 °C or higher and a relative dielectric constant of 6.0 or higher, is 0.1 to 1.0 in terms of the mass ratio represented by the second solvent / the first solvent.

3. The soldering flux according to claim 1, wherein, The mass ratio of the polyamide to the second solvent, which is the compound represented by the above general formula (1) having a boiling point of 250 °C or higher and a relative dielectric constant of 6.0 or higher, is 0.15 to 0.4 in terms of the mass ratio represented by the polyamide / the second solvent.

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

5. A solder paste containing a solder alloy powder and the soldering flux according to any one of claims 1 to 4.

6. A method for preparing a joined body, which includes a step of obtaining a joined body by welding a component and a substrate, During the welding, the solder paste according to claim 5 is used, and reflow soldering is performed in a reducing gas atmosphere.

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