Flux composition, solder composition, and electronic substrate

Abstract

To provide a flux composition which can suppress occurrence of heating droop.SOLUTION: A flux composition contains (A) a rosin-based resin, (B) an activator, (C) a thixotropic agent, and (D) a solvent, wherein the component (C) contains (C1) 1,3:2,4-bis-O-benzylidene-D-glucitol, and the component (D) contains (D1) imidazolidinones represented by the following general formula (1). In the general formula (1), R1 and R4 are independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an alkenyl group having 2 to 8 carbon atoms; R2 and R3 are independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkenyl group having 2 to 4 carbon atoms; and R2 and R3 may be bonded to each other and form a ring.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a flux composition, a solder composition, and an electronic substrate.

Background Art

[0002] A solder composition is a mixture obtained by kneading a flux composition (such as a rosin-based resin, an activator, and a solvent) with solder powder to form a paste (see Patent Document 1). In recent years, as solder, lead-free solder that does not contain lead (Pb) has been widely used in consideration of environmental problems. On the other hand, in printed wiring boards, small components are densely mounted in a narrow area. Therefore, it has become important that no solder sag occurs during heating of the solder composition so as not to affect adjacent small components.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a flux composition and a solder composition capable of suppressing the occurrence of solder sag, and an electronic substrate using the same.

Means for Solving the Problems

[0005] According to one aspect of the present invention, there is provided a solder composition containing (A) a rosin-based resin, (B) an activator, (C) a thixotropic agent, and (D) a solvent, wherein the component (C) contains (C1) 1,3:2,4-bis-O-benzylidene-D-glucitol, and the component (D) contains (D1) imidazolidinones represented by the following general formula (1).

[0006]

Chemical Formula

[0007] In general formula (1), R 1 and R 4 are independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an alkenyl group having 2 to 8 carbon atoms, and R 2 and R 3 are independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkenyl group having 2 to 4 carbon atoms, and R 2 and R 3 may combine to form a ring.

[0008] According to one aspect of the present invention, there is provided a solder composition containing the flux composition according to one aspect of the present invention and (E) solder powder.

[0009] According to one aspect of the present invention, there is provided an electronic substrate including a soldered portion using the solder composition according to one aspect of the present invention.

Effects of the Invention

[0010] According to the present invention, it is possible to provide a flux composition, a solder composition, and an electronic substrate using these, which can suppress the generation of heating sag.

Modes for Carrying Out the Invention

[0011] The solder composition according to the present embodiment contains a flux composition containing (A) a rosin-based resin, (B) an activator, (C) a thixotropic agent, and (D) a solvent, and (E) solder powder, and the component (C) contains (C1) 1,3:2,4-bis-O-benzylidene-D-glucitol, and the component (D) contains (D1) imidazolidinones represented by the general formula (1).

[0012] According to the present embodiment, the reason why a solder composition capable of suppressing the generation of heating sag can be obtained is not necessarily clear, but the present inventors presume as follows. That is, the solder composition according to this embodiment contains a dibenzylidene sorbitol-based thixotropic agent such as (C1) 1,3:2,4-bis-O-benzylidene-D-glucitol. This thixotropic agent can suppress the occurrence of heating sag during reflow. However, when using a dibenzylidene sorbitol-based thixotropic agent in a solder composition, heating and dissolution or dispersion by a roll mill are required. And since the solder composition contains an acidic component, benzaldehydes are liberated from the dibenzylidene sorbitol-based thixotropic agent due to such heating and dissolution, resulting in a problem that the effect of suppressing heating sag cannot be obtained. In contrast, the solder composition according to this embodiment contains (D1) imidazolidinones, which can dissolve the (C1) component. And when the (C1) component dissolves in the (D1) component, the effect of suppressing heating sag can be exhibited without performing heating and dissolution or the like. The inventors of the present invention surmise that the effects of the present invention are achieved in the above manner. Note that the (D1) component is not a substance subject to regulation at present and can be used as a solvent for the solder composition.

[0013] [Flux Composition] First, the flux composition used in this embodiment will be described. The flux composition used in this embodiment is a component other than the solder powder in the solder composition and contains the following (B) activator, (C) thixotropic agent, and (D) solvent to be described below.

[0014] [Component (A)] Examples of the (A) rosin-based resin used in this embodiment include rosins and rosin-based modified resins. Examples of rosins include gum rosin, wood rosin, and tall oil rosin. Examples of rosin-based modified resins include disproportionated rosin, polymerized rosin, hydrogenated rosin, formylated rosin, and derivatives thereof. Examples of hydrogenated rosin include fully hydrogenated rosin, partially hydrogenated rosin, and hydrogenated products of unsaturated organic acid-modified rosins (also referred to as "hydrogenated acid-modified rosins") which are modified rosins of unsaturated organic acids (such as aliphatic unsaturated monobasic acids such as (meth)acrylic acid, aliphatic unsaturated dibasic acids such as α,β-unsaturated carboxylic acids such as fumaric acid and maleic acid, and unsaturated carboxylic acids having an aromatic ring such as cinnamic acid). These rosin-based resins may be used alone or in combination of two or more. Among these rosin-based resins, from the viewpoint of the balance of various physical properties, it is preferably at least one selected from the group consisting of hydrogenated rosin and formylated rosin.

[0015] The blending amount of component (A) is preferably 30% by mass or more and 60% by mass or less, more preferably 40% by mass or more and 50% by mass or less, based on 100% by mass of the flux composition. If the blending amount of component (A) is at least the above lower limit, the oxidation of the copper foil surface of the soldering land can be prevented, and the so-called solderability can be improved so that the molten solder wets the surface well, and solder balls can be sufficiently suppressed. Also, if the blending amount of component (A) is at most the above upper limit, the amount of flux residue can be sufficiently suppressed.

[0016] [Component (B)] Examples of the (B) activator used in this embodiment include organic acids, non-dissociative activators composed of non-dissociative halogenated compounds (halogen-based activators), and amine-based activators. These activators may be used alone or in combination of two or more. Examples of organic acids include monocarboxylic acids, dicarboxylic acids, and other organic acids. Examples of monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, tuberculostearic acid, arachidic acid, behenic acid, lignoceric acid, glycolic acid, and the like. Examples of dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, tartaric acid, diglycolic acid, and the like. Examples of other organic acids include dimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anisic acid, citric acid, picolinic acid, and the like.

[0017] Examples of the non-dissociative activator composed of a non-dissociative halogenated compound include non-salt organic compounds in which halogen atoms are bonded by covalent bonds. Examples of such halogenated compounds include compounds formed by covalent bonds of individual elements such as chlorine, bromine, and fluorine, such as chlorides, bromides, and fluorides. However, compounds having covalent bonds of any two or all of chlorine, bromine, and fluorine may also be used. In order to improve the solubility in an aqueous solvent, these compounds preferably have polar groups such as hydroxyl groups and carboxyl groups, such as halogenated alcohols and halogenated carboxyls. Examples of halogenated alcohols include brominated alcohols such as 2,3-dibromopropanol, 2,3-dibromobutanediol, trans-2,3-dibromo-2-butene-1,4-diol, 1,4-dibromo-2-butanol, and tribromoneopentyl alcohol; chlorinated alcohols such as 1,3-dichloro-2-propanol and 1,4-dichloro-2-butanol; fluorinated alcohols such as 3-fluorocatechol; and other similar compounds. Examples of halogenated carboxyls include iodinated carboxyls such as 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, and 5-iodoanthranilic acid; chlorinated carboxyls such as 2-chlorobenzoic acid and 3-chloropropionic acid; brominated carboxyls such as 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid, and 2-bromobenzoic acid; and other similar compounds.

[0018] Examples of amine-based activators include amines (such as polyamines such as ethylenediamine), amine salts (such as amines such as trimethylolamine, cyclohexylamine, and diethylamine, and organic acid salts and inorganic acid salts (such as hydrochloric acid, sulfuric acid, and hydrobromic acid) of amino alcohols), amino acids (such as glycine, alanine, aspartic acid, glutamic acid, and valine), and amide-based compounds. Specifically, examples include diphenylguanidine hydrobromide, cyclohexylamine hydrobromide, diethylamine salts (such as hydrochloride, succinate, adipate, and sebacate), triethanolamine, monoethanolamine, and hydrobromide salts of these amines.

[0019] (B) The blending amount of the component varies depending on other components and the alloy composition of the solder powder used, but is usually 20% by mass or less with respect to 100% by mass of the flux composition. The lower limit may be, for example, 0.1% by mass or more.

[0020] [Component (C)] The thixotropic agent (C) used in this embodiment needs to contain (C1) 1,3:2,4 - bis - O - benzylidene - D - glucitol. The combination of this (C1) component and the (D1) component described later can suppress the occurrence of heating sag.

[0021] The blending amount of the (C1) component is preferably 0.1% by mass or more and 5% by mass or less, and more preferably 0.5% by mass or more and 2% by mass or less with respect to 100% by mass of the flux composition. If the blending amount of the (C1) component is above the lower limit, the suppression effect of heating sag can be further improved. Even if the blending amount of the (C1) component exceeds the upper limit, no further suppression effect of heating sag can be obtained.

[0022] The thixotropic agent (C) used in this embodiment may further contain a thixotropic agent other than the (C1) component (hereinafter also referred to as the (C2) component) from the viewpoint of printability and the like. Examples of the (C2) component used here include hydrogenated castor oil, amides, kaolin, colloidal silica, organic bentonite, and glass frit. These may be used alone or in combination of two or more. Also, from the viewpoint of printability and the like, the (C2) component is preferably a thixotropic agent having a melting point of 100°C or lower. Examples of the thixotropic agent having a melting point of 100°C or lower include hydrogenated castor oil. When using the (C2) component, its blending amount is preferably 3% by mass or more and 12% by mass or less, and more preferably 5% by mass or more and 10% by mass or less with respect to 100% by mass of the flux composition. If the blending amount is less than the lower limit, thixotropy cannot be obtained and printing sag tends to occur. On the other hand, if it exceeds the upper limit, the thixotropy is too high and printing defects tend to occur.

[0023] The blending amount of component (C) is preferably 2% by mass or more and 15% by mass or less, more preferably 5% by mass or more and 10% by mass or less, based on 100% by mass of the flux composition. If the blending amount is less than the lower limit, thixotropy cannot be obtained and printing drip tends to occur. On the other hand, if it exceeds the upper limit, the thixotropy is too high and printing defects tend to occur.

[0024] [Component (D)] The solvent (D) used in this embodiment needs to contain imidazolidinones represented by the following general formula (1). By this component (D1), component (C1) can be dissolved and the effect of suppressing heating drip due to component (C1) can be exerted.

[0025] [Chemical formula]

[0026] In general formula (1), R 1 and R 4 are independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an alkenyl group having 2 to 8 carbon atoms. Among these, an alkyl group having 1 to 4 carbon atoms or an alkenyl group having 2 to 4 carbon atoms is preferable, and a methyl group is more preferable. R 2 and R 3 are independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkenyl group having 2 to 4 carbon atoms. Among these, a hydrogen atom, a methyl group, or an alkenyl group having 2 to 4 carbon atoms is preferable, a hydrogen atom or a methyl group is more preferable, and a hydrogen atom is particularly preferable. Also, R 2 and R 3 may be bonded to form a ring.

[0027] From the viewpoint of dissolving component (C1) at normal temperature, component (D1) is preferably liquid at 25°C. (D1) component preferably has a boiling point of 170 °C or higher, more preferably 200 °C or higher, from the viewpoint of printability and the like. In this specification, the boiling point refers to the boiling point at 1013 hPa. Examples of the (D1) component include 1,3-dimethyl-2-imidazolidinone (boiling point 221 °C), 1,3-bis(2-methylpropyl)-2-imidazolidinone, 1-heptyl-3-methyl-2-imidazolidinone (boiling point 289 to 297 °C), 1,3,4-trimethyl-2-imidazolidinone, 1,3-diethenyl-1,3-dihydro-2H-benzimidazol-2-one, and 1,3-dimethyl-2-imidazolidinone (solid at 25 °C). Among these, from the above viewpoints, 1,3-dimethyl-2-imidazolidinone, 1,3-bis(2-methylpropyl)-2-imidazolidinone, 1-heptyl-3-methyl-2-imidazolidinone, or 1,3,4-trimethyl-2-imidazolidinone is preferred, and 1,3-dimethyl-2-imidazolidinone or 1-heptyl-3-methyl-2-imidazolidinone is more preferred.

[0028] The blending amount of the (D1) component is preferably 1% by mass or more and 15% by mass or less, more preferably 3% by mass or more and 12% by mass or less, and even more preferably 5% by mass or more and 10% by mass or less, based on 100% by mass of the flux composition, from the viewpoint of dissolving the (C1) component. Also, from the viewpoint of more surely dissolving the (C1) component, the mass ratio (D1 / C1) of the (D1) component to the (C1) component is preferably 4 or more and 30 or less, more preferably more than 4 and 20 or less, even more preferably 5 or more and 15 or less, and particularly preferably 6 or more and 10 or less.

[0029] The (D) solvent used in this embodiment may further contain a solvent other than the (D1) component (hereinafter also referred to as the (D2) component) from the viewpoint of printability and the like. As the (D2) component used here, known solvents can be appropriately used. As such a solvent, a solvent having a boiling point of 170 °C or higher is preferably used. Also, glycol-based solvents are preferred. Examples of such solvents include diethylene glycol, dipropylene glycol, triethylene glycol, hexylene glycol, hexyl diglycol, 1,5 - pentanediol, methyl carbitol, butyl carbitol, 2 - ethylhexyl diglycol (EHDG), octanediol, phenyl glycol, diethylene glycol monohexyl ether, tetraethylene glycol dimethyl ether, and dibutyl maleate. These solvents may be used alone or in combination of two or more.

[0030] The blending amount of component (D) is preferably 10% by mass or more and 60% by mass or less, more preferably 20% by mass or more and 50% by mass or less, based on 100% by mass of the flux composition. If the blending amount of the solvent is within the above range, the viscosity of the resulting solder composition can be appropriately adjusted to an appropriate range.

[0031] [Other components] In addition to components (A), (B), (C), and (D), other additives and even other resins can be added to the flux composition used in this embodiment, if necessary. Examples of other additives include antioxidants, defoamers, modifiers, matting agents, and foaming agents. The blending amount of these additives is preferably 0.01% by mass or more and 5% by mass or less based on 100% by mass of the flux composition. Examples of other resins include acrylic resins.

[0032] [Solder composition] Next, the solder composition of this embodiment will be described. The solder composition of this embodiment contains the above - described flux composition of this embodiment and (E) solder powder described below. The blending amount of the flux composition is preferably 5% by mass or more and 35% by mass or less, more preferably 7% by mass or more and 15% by mass or less, and particularly preferably 8% by mass or more and 12% by mass or less with respect to 100% by mass of the solder composition. When the blending amount of the flux composition is less than 5% by mass (when the blending amount of the solder powder exceeds 95% by mass), the flux composition as a binder is insufficient, and thus it tends to be difficult to mix the flux composition and the solder powder. On the other hand, when the blending amount of the flux composition exceeds 35% by mass (when the blending amount of the solder powder is less than 65% by mass), it tends to be difficult to form a sufficient solder joint when the obtained solder composition is used.

[0033] [Component (E)] The (E) solder powder used in the present invention preferably consists only of lead-free solder powder, but may be leaded solder powder. Further, the solder alloy in this solder powder preferably contains at least one selected from the group consisting of tin (Sn), copper (Cu), zinc (Zn), silver (Ag), antimony (Sb), lead (Pb), indium (In), bismuth (Bi), nickel (Ni), cobalt (Co), and germanium (Ge). As the solder alloy in this solder powder, an alloy mainly composed of tin is preferable. Further, this solder alloy more preferably contains tin, silver, and copper. Furthermore, this solder alloy may contain at least one of antimony, bismuth, and nickel as an additive element. Here, the lead-free solder powder refers to a powder of a solder metal or alloy to which no lead is added. However, the presence of lead as an unavoidable impurity in the lead-free solder powder is allowed, and in this case, the amount of lead is preferably 300 ppm by mass or less.

[0034] Specific examples of the alloy systems of lead-free solder powder include Sn-Ag-Cu, Sn-Cu, Sn-Ag, Sn-Bi, Sn-Ag-Bi, Sn-Ag-Cu-Bi, Sn-Ag-Cu-Ni, Sn-Ag-Cu-Bi-Sb, Sn-Ag-Bi-In, Sn-Ag-Cu-Bi-In-Sb, and the like.

[0035] (E) The average particle size is usually 1 μm or more and 40 μm or less. From the perspective of also being compatible with electronic substrates having a narrow pitch of solder pads, it is more preferably 1 μm or more and 35 μm or less, even more preferably 2 μm or more and 35 μm or less, and particularly preferably 3 μm or more and 32 μm or less. The average particle size can be measured by a dynamic light scattering type particle size measuring device.

[0036] [Method for manufacturing solder composition] The solder composition of the present embodiment can be manufactured by blending the flux composition described above and the (E) solder powder described above at the above-mentioned predetermined ratio and stirring and mixing them.

[0037] [Electronic substrate] Next, the electronic substrate of the present embodiment will be described. The electronic substrate of the present embodiment is characterized by including a soldering portion using the solder composition described above. The electronic substrate of the present embodiment can be manufactured by mounting electronic components on an electronic substrate (such as a printed wiring board) using the above-mentioned solder composition. Examples of the coating device used here include a screen printer, a metal mask printer, a dispenser, and a jet dispenser. Also, electronic components can be mounted on the electronic substrate through a reflow process in which the electronic components are placed on the solder composition coated by the coating device and heated under predetermined conditions by a reflow furnace to mount the electronic components on the printed wiring board.

[0038] In the reflow process, the electronic component is placed on the solder composition and heated under predetermined conditions by a reflow furnace. Through this reflow process, sufficient solder bonding can be achieved between the electronic component and the printed wiring board. As a result, the electronic component can be mounted on the printed wiring board. The reflow conditions may be appropriately set according to the melting point of the solder. For example, the preheat temperature is preferably 100°C or higher and 180°C or lower. The preheat time is preferably 20 seconds or longer and 120 seconds or shorter. The peak temperature is preferably 238°C or higher and 260°C or lower, and more preferably 238°C or higher and 245°C or lower. Also, the holding time at a temperature of 220°C or higher is preferably 20 seconds or longer and 60 seconds or shorter.

[0039] Moreover, the solder composition and the electronic substrate of the present embodiment are not limited to the above embodiment, and modifications, improvements, etc. within the scope that can achieve the object of the present invention are included in the present invention. For example, in the above electronic substrate, the printed wiring board and the electronic component are adhered by the reflow process, but it is not limited thereto. For example, instead of the reflow process, the printed wiring board and the electronic component may be adhered by a process of heating the solder composition using a laser beam (laser heating process). In this case, the laser light source is not particularly limited and can be appropriately adopted according to the wavelength corresponding to the absorption band of the metal. Examples of the laser light source include solid-state lasers (such as ruby, glass, YAG, etc.), semiconductor lasers (such as GaAs and InGaAsP, etc.), liquid lasers (such as dyes, etc.), and gas lasers (such as He-Ne, Ar, CO 2 , and excimer, etc.).

Examples

[0040] Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited by these examples. The materials used in the examples and comparative examples are shown below. (Component (A)) Rosin resin A: fully hydrogenated rosin, trade name "Foral AXE", manufactured by Eastman Chemical Company Rosin resin B: formylated rosin, trade name "FG-90", manufactured by Harima Chemicals, Inc. (Component (B)) Activator A: tris(2,3-dibromopropyl)isocyanurate, trade name "Taic-6B", manufactured by Nippon Kasei Co., Ltd. Activator B: glutaric acid (Component (C1)) Thixotropic agent A: 1,3:2,4-bis-O-benzylidene-D-glucitol (melting point 210 - 230°C), trade name "Gelol D", manufactured by Shin Nippon Rika Co., Ltd. (Component (C2)) Thixotropic agent B: castor hardened oil (melting point 85 - 87°C), trade name "Himakou", manufactured by K.F. Trading Co., Ltd. Thixotropic agent C: dibenzylidene sorbitol-based thixotropic agent (1,3:2,4-bis-O-(4-methylbenzylidene)-D-sorbitol, melting point 255 - 267°C), trade name "Gelol MD", manufactured by Shin Nippon Rika Co., Ltd. Thixotropic agent D: polyamide, trade name "Talen VA-79", manufactured by Kyoeisha Chemical Co., Ltd. (Component (D1)) Solvent A: 1,3-dimethyl-2-imidazolidinone (boiling point 221°C), manufactured by Mitsui Chemicals, Inc. (Component (D2)) Solvent B: 2-ethylhexyl diglycol (EHDG), manufactured by Nippon Emulsion Co., Ltd. (Component (E)) Solder powder: alloy composition is Sn-3.0Ag-0.5Cu, particle size distribution is 1 - 12 μm (corresponding to type 7 of IPC-J-STD-005A), solder melting point is 217 - 220°C

[0041] [Examples 1 - 4 and Comparative Examples 1 - 3] Each component was kneaded with the composition and formulation shown in Table 1 to prepare each flux composition and each solder composition according to Examples 1 - 4 and Comparative Examples 1 - 3. The unit of the numerical values representing the composition is mass% unless otherwise specified.

[0042] (Evaluation of solder composition) The evaluation (heating sag) of the solder composition was conducted by the following method. The obtained results are shown in Table 1. (1) Heating sag For the evaluation of heating sag, an evaluation substrate (solder resist opening width: 100 μm, surface treatment: water-soluble preflux), a metal mask (mask opening: 250 μm, metal mask thickness: 50 μm), and a squeegee (metal squeegee) were prepared. Next, the obtained solder composition was printed onto the evaluation substrate and heated in a hot air oven at 190 °C for 90 seconds. The diameters of the printed solder before and after heating were measured. The size of the spread of the solder composition due to heating (heating sag width) was calculated. Then, the heating sag was evaluated according to the following criteria. ◎: The heating sag width is less than 10 μm. 〇: The heating sag width is 10 μm or more and less than 15 μm. △: The heating sag width is 15 μm or more and less than 20 μm. ×: The heating sag width is 20 μm or more.

[0043]

Table 1

[0044] As is clear from the results shown in Table 1, it was confirmed that the solder compositions of the present invention (Examples 1 to 4) had good heating sag results. On the other hand, when a dibenzylidene sorbitol-based thixotropic agent other than the (C1) component (thixotropic agent C) was used (Comparative Example 1), the thixotropic agent C did not dissolve in the solvent A which is the (D1) component, high-temperature heating was required, and it is presumed that due to the decomposition of the thixotropic agent C, the effect of suppressing heating sag could not be exhibited. Also, when the (C1) component was not contained (Comparative Examples 2 and 3), it was found that heating sag could not be suppressed. Therefore, it was confirmed that the solder composition of the present invention can suppress the occurrence of heating sag.

Industrial Applicability

[0045] The solder composition of the present invention can be suitably used as a technique for mounting electronic components on an electronic substrate such as a printed wiring board of an electronic device.

Claims

1. A flux composition containing (A) a rosin-based resin, (B) an activator, (C) a thixotropic agent, and (D) a solvent, wherein the component (C) contains (C1) 1,3:2,4-bis-O-benzylidene-D-glucitol, and the component (D) contains (D1) imidazolidinones represented by the following general formula (1). Flux composition. 【Chemical 1】 (In general formula (1), R １ and R ４ are independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an alkenyl group having 2 to 8 carbon atoms, and R ２ and R ３ are independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkenyl group having 2 to 4 carbon atoms, and R ２ and R ３ may combine to form a ring.)

2. The flux composition according to Claim 1, wherein the component (D1) is 1,3-dimethyl-2-imidazolidinone. Flux composition.

3. The flux composition according to Claim 1 or Claim 2, wherein the component (A) is at least one selected from the group consisting of hydrogenated rosin and formylated rosin. Flux composition.

4. A solder composition containing the flux composition according to any one of Claims 1 to 3 and (E) solder powder. Solder composition.

5. An electronic substrate provided with a soldered portion using the solder composition according to Claim 4. Electronic substrate.

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