Flux composition, solder composition, and electronic substrate

Abstract

To provide a flux composition that can sufficiently suppress voids and exhibits high storage stability.SOLUTION: A flux composition comprises (A) a resin, (B) an activator, and (C) a solvent. The component (C) comprises (C1) a solvent with a boiling point of higher than 250°C and a viscosity of more than 10 mPa s at 20°C and (C2) a diol solvent with a boiling point of 250°C or lower and a resistance value of 60 MΩ or more and 80 MΩ or less, comprising two hydroxy groups in one molecule.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] The solder composition is a paste-like mixture made by kneading solder powder with a flux composition (rosin-based resin, activator, solvent, etc.) (see, for example, Patent Document 1). This solder composition is required to have solderability, such as solder meltability and solder wetting and spreading properties (solder wetting and spreading), as well as void suppression and printability. On the other hand, as the functions of electronic devices become more diverse, larger electronic components are being mounted on electronic boards. Among these large electronic components, there are those with large electrode terminal areas (e.g., QFN (Quad Flatpack No Lead) and power transistors). These electronic components tend to be prone to voids due to the large printing area of ​​the solder composition. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5756067 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to reduce voids in solder compositions, the use of high-viscosity solvents such as diol-based solvents has been considered. However, diol-based solvents tend to have relatively high viscosity and high polarity, which tends to reduce the storage stability of the solder composition.

[0005] An object of the present invention is to provide a flux composition, a solder composition, and an electronic substrate that can sufficiently suppress voids and have excellent storage stability. [Means for solving the problem]

[0006] According to the present invention, there are provided the following flux composition, solder composition, and electronic substrate. [1] A flux composition comprising (A) a resin, (B) an activator, and (C) a solvent, the component (C) contains (C1) a solvent having a boiling point of more than 250°C and a viscosity at 20°C of more than 10 mPa·s, and (C2) a diol solvent having a boiling point of 250°C or less, a resistance value of 60 MΩ or more and 80 MΩ or less, and two hydroxy groups in one molecule; Flux composition. [2] In the flux composition according to [1], The component (B) contains (B1) a dicarboxylic acid having 6 or more carbon atoms. Flux composition. [3] The flux composition according to [1] or [2], the component (C) further contains (C3) a solvent having a boiling point of 210°C or higher and 275°C or lower and a viscosity at 20°C of 10 mPa s or lower; Flux composition. [4] The flux composition according to any one of [1] to [3], The component (C1) is diethylene glycol mono-2-ethylhexyl ether. Flux composition. [5] The flux composition according to any one of [1] to [4], Further, (D) a thixotropic agent is contained, The component (D) contains an amide. Flux composition. [6] The flux composition according to any one of [1] to [5], Further, (E) a hindered amine compound is contained, Flux composition. [7] The flux composition according to any one of [1] to [6], Further, (F) a hindered phenol-based antioxidant is contained, Flux composition. [8] A flux composition according to any one of [1] to [7] and (G) a solder powder. Solder composition. [9] [8] A soldered portion using the solder composition according to the present invention. Electronic board. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to provide a flux composition, a solder composition, and an electronic substrate that can sufficiently suppress voids and have excellent storage stability. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Flux composition] First, the flux composition according to this embodiment will be described. The flux composition according to this embodiment contains the components other than the solder powder in the solder composition: (A) resin, (B) activator, and (C) solvent, which will be described below. Furthermore, component (C) must contain (C1) a solvent having a boiling point greater than 250°C and a viscosity at 20°C greater than 10 mPa·s, and (C2) a diol-based solvent having a boiling point of 250°C or less, a resistivity of 60 MΩ or more and 80 MΩ or less, and two hydroxy groups per molecule.

[0009] The reason why the flux composition according to this embodiment can sufficiently suppress voids and improve printability is not entirely clear, but the inventors speculate as follows. Specifically, the flux composition of the present invention uses, as the solvent (C), a diol-based solvent (C2) having a boiling point of 250°C or less, a resistivity of 60 MΩ to 80 MΩ, and two hydroxyl groups per molecule. A portion of the component (C2) volatilizes and becomes gas before or during solder melting. This gas expels gases from the solder composition. Furthermore, the solder composition containing the non-volatilized component (C2) retains a certain degree of fluidity even during solder melting, allowing the gases in the solder composition to gradually gather and be released to the outside. In this way, voids can be sufficiently suppressed. Furthermore, the component (C2) tends to have low polarity among diol-based solvents. This suppresses viscosity changes during storage of the solder composition, despite the use of a diol-based solvent. Thus, excellent storage stability can be ensured. The inventors believe that the above-mentioned effects of the present invention are achieved in this manner.

[0010] [Component (A)] Examples of the resin (A) used in this embodiment include rosin resins, acrylic resins, epoxy resins, and phenolic resins. These may be used alone or in combination of two or more. Among these, rosin resins and acrylic resins are preferred from the viewpoint of viscosity stability. Examples of rosin-based resins include rosins and rosin-modified resins. Examples of rosins include gum rosin, wood rosin, and tall oil rosin. Examples of rosin-modified resins include disproportionated rosin, polymerized rosin, hydrogenated rosin, and derivatives thereof. Examples of hydrogenated rosins include fully hydrogenated rosin, partially hydrogenated rosin, and hydrogenated products of unsaturated organic acid-modified rosins (also referred to as "hydrogenated acid-modified rosin"), which are rosins modified with 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, fully hydrogenated rosin and hydrogenated acid-modified rosin are preferred, and a combination of fully hydrogenated rosin and hydrogenated acid-modified rosin is more preferred. Acrylic resins are obtained by polymerizing at least one monomer, such as acrylic acid, methacrylic acid, various esters of acrylic acid, various esters of methacrylic acid, crotonic acid, itaconic acid, maleic acid, maleic anhydride, esters of maleic acid, esters of maleic anhydride, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, vinyl chloride, and vinyl acetate. Acrylic resins are useful because they can prevent cracking in flux residues, even in environments with large temperature differences and thermal shocks. Among these acrylic resins, acrylic resins obtained by polymerizing monomers containing methacrylic acid and a monomer having an alkyl group containing 2 to 6 carbon atoms, and acrylic resins obtained by polymerizing monomers containing methacrylic acid and a monomer having an alkyl group containing 2 carbon atoms, are preferred. These acrylic resins are preferred because they reduce the stickiness of the resulting flux residue (solidified flux) and provide good crack suppression.

[0011] The blending amount of component (A) is preferably 25% by mass to 60% by mass, and more preferably 30% by mass to 50% by mass, based on 100% by mass of the flux composition. When the blending amount of component (A) is above the lower limit, oxidation of the copper foil surface of the soldering land is prevented, making the surface more easily wetted by molten solder, improving so-called solderability and sufficiently suppressing solder balls. Furthermore, when the blending amount of component (A) is below the upper limit, the amount of flux residue can be sufficiently suppressed.

[0012] [(B) Component] The (B) activator used in this embodiment preferably contains (B1) a dicarboxylic acid having 6 or more carbon atoms. This (B1) component can improve solderability. Examples of the component (B1) include adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, eicosanedioic acid, and 8,13-dimethyl-8,12-eicosadienedioic acid. These may be used alone or in combination of two or more.

[0013] The blending amount of component (B1) is preferably 0.1% by mass to 15% by mass, more preferably 1% by mass to 12% by mass, even more preferably 3% by mass to 10% by mass, and particularly preferably 5% by mass to 8% by mass, based on 100% by mass of the flux composition. If the blending amount of component (B1) is equal to or greater than the lower limit, solderability tends to be improved without deteriorating other physical properties, while if it is equal to or less than the upper limit, the insulating properties of the flux composition tend to be maintained.

[0014] Component (B) may further contain (B2) an amine-based activator, which can further improve solderability. Examples of component (B2) include benzotriazoles (benzotriazole, 2-(2-hydroxy-5-methylphenyl), etc.), imidazolines (2-phenylimidazoline, 2-benzylimidazoline, etc.), amines (polyamines such as ethylenediamine), amine salts (organic acid salts or inorganic acid salts (hydrochloric acid, sulfuric acid, hydrobromic acid, etc.) of amines such as trimethylolamine, cyclohexylamine, diethylamine, and amino alcohols), amino acids (glycine, alanine, aspartic acid, glutamic acid, valine, etc.), amide compounds, etc. Among these, imidazolines are preferred from the viewpoint of activity.

[0015] The blending amount of component (B2) is preferably 0.1% by mass to 10% by mass, more preferably 0.5% by mass to 8% by mass, even more preferably 1% by mass to 7% by mass, and particularly preferably 3% by mass to 6% by mass, based on 100% by mass of the flux composition. If the blending amount of component (B2) is equal to or greater than the lower limit, solderability tends to be improved, while if it is equal to or less than the upper limit, the insulating properties of the flux composition tend to be maintained.

[0016] The component (B) may further contain an organic acid other than the component (B1) (hereinafter sometimes referred to as the component (B3)). Examples of the component (B3) include monocarboxylic acids, dicarboxylic acids other than the component (B1), and other organic acids. These may be used alone or in combination of two or more. 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, and glycolic acid. Dicarboxylic acids include succinic acid, dimer acid, tartaric acid, and diglycolic acid. Other organic acids include trimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anisic acid, citric acid, and picolinic acid, etc. Among these, picolinic acid is more preferably used.

[0017] When component (B3) is used, its amount is preferably 0.1% by mass to 8% by mass, more preferably 0.2% by mass to 5% by mass, and particularly preferably 0.3% by mass to 3% by mass, based on 100% by mass of the flux composition. If the amount of component (B3) is equal to or greater than the lower limit, the activation effect tends to be improved, while if it is equal to or less than the upper limit, the insulating properties of the flux composition tend to be maintained.

[0018] In addition to components (B1) to (B3), component (B) may further contain another activator (hereinafter also referred to as component (B4)) within the scope of the present invention. Examples of component (B4) include halogen-based activators.

[0019] The blending amount of component (B) is preferably 1% by mass or more and 20% by mass or less, and more preferably 2% by mass or more and 15% by mass or less, based on 100% by mass of the flux composition. If the blending amount of component (B) is equal to or more than the lower limit, the activation action tends to be improved, while if it is equal to or less than the upper limit, the insulating properties of the flux composition tend to be maintained.

[0020] [(C) component] The solvent (C) used in this embodiment must contain a solvent (C1) having a boiling point of more than 250° C. and a viscosity of more than 10 mPa s at 20° C. This component (C1) is the main solvent, and it allows the viscosity of the solder composition to fall within an appropriate range during printing and after reflow. Examples of component (C1) include diethylene glycol mono-2-ethylhexyl ether (boiling point 272°C, viscosity 11.8 mPa·s) and polyethylene glycol monomethyl ether (boiling point 290-310°C, viscosity 12.8 mPa·s). Among these, diethylene glycol mono-2-ethylhexyl ether is preferred from the viewpoint of printability. These may be used alone or in combination of two or more. The viscosity in parentheses is the viscosity at 20°C.

[0021] The blending amount of component (C1) is preferably 40% by mass or more and 85% by mass or less, more preferably 45% by mass or more and 80% by mass or less, and particularly preferably 50% by mass or more and 75% by mass or less, relative to 100% by mass of component (C).

[0022] The solvent (C) used in this embodiment must contain a diol solvent (C2) having a boiling point of 250° C. or less, a resistance of 60 MΩ to 80 MΩ, and two hydroxyl groups per molecule. This component (C2) is highly effective in suppressing voids and has little adverse effect on storage stability. The resistance value of the solvent can be measured using a Milliohm HiTester (manufactured by Hioki E.E. Corp.) The temperature of the solvent during measurement may be room temperature (for example, 25°C). Examples of the component (C2) include 1,2-butanediol (resistance value 65 MΩ), 1,2-pentanediol (resistance value 70 MΩ), and 1,2-hexanediol (resistance value 70 MΩ). These may be used alone or in combination of two or more.

[0023] The blending amount of component (C2) is preferably 10% by mass to 50% by mass, more preferably 15% by mass to 45% by mass, and particularly preferably 20% by mass to 40% by mass, based on 100% by mass of component (C). If the blending amount of component (C2) is equal to or greater than the lower limit, the void suppression effect can be further enhanced. On the other hand, if the blending amount of component (C2) is equal to or less than the upper limit, adverse effects on storage stability can be suppressed.

[0024] The (C) solvent used in this embodiment preferably contains (C3) a solvent having a boiling point of 210° C. or higher and 275° C. or lower and a viscosity of 10 mPa·s or lower at 20° C. Such a (C3) component can improve printability. Examples of component (C3) include diethylene glycol dibutyl ether (boiling point 256°C, viscosity 2.4 mPa·s), diethylene glycol butyl methyl ether (boiling point 212°C, viscosity 1.6 mPa·s), tetraethylene glycol dimethyl ether (boiling point 275°C, viscosity 3.8 mPa·s), diethylene glycol monobutyl ether (boiling point 230°C, viscosity 5.85 mPa·s), and diethylene glycol monobutyl ether acetate (boiling point 247°C, viscosity 3.56 mPa·s). Note that the viscosity in parentheses is at 20°C.

[0025] From the viewpoint of printability, the blending amount of the (C3) component is preferably 5% by mass or more and 30% by mass or less, more preferably 8% by mass or more and 22% by mass or less, and particularly preferably 10% by mass or more and 15% by mass or less, relative to 100% by mass of the (C) component.

[0026] From the viewpoint of the balance between the void suppression effect and printability, the mass ratio of the (C2) component to the (C3) component ((C2) / (C3)) is preferably 1 / 2 or more and 6 or less, more preferably 1 or more and 5 or less, and particularly preferably 3 / 2 or more and 4 or less.

[0027] Component (C) may contain a solvent other than components (C1), (C2), and (C3) (hereinafter also referred to as component (C4)). A known solvent can be used as component (C4). Preferably, such a solvent has a boiling point of 170°C or higher and 250°C or lower. Examples of such solvents include hexylene glycol (boiling point 197° C.) and methyl carbitol (boiling point 194° C.), etc. These may be used alone or in combination of two or more. From the viewpoint of storage stability, it is preferable not to use a diol solvent other than the component (C2) as the component (C).

[0028] The blending amount of component (C) is preferably 20% by mass to 60% by mass, and more preferably 30% by mass to 50% by mass, 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.

[0029] [(D) component] The flux composition according to this embodiment preferably contains a thixotropic agent (D) from the viewpoint of suppressing sagging during printing or heating. A known thixotropic agent can be used as component (D). Examples of thixotropic agents used here include hydrogenated castor oil, amides, kaolin, colloidal silica, organic bentonite, and glass frit. Among these, amides are preferred from the viewpoint of storage stability. These agents may be used alone or in combination of two or more. From the viewpoint of storage stability, it is preferable not to use a thixotropic agent other than an amide (particularly, hydrogenated castor oil) as component (D).

[0030] The blending amount of component (D) is preferably 2% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 15% by mass or less, and particularly 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 above the lower limit, sufficient thixotropy is obtained and sagging tends to be suppressed. On the other hand, if the blending amount is below the upper limit, thixotropy is not too high and printing defects tend to be less likely to occur.

[0031] [(E) component] From the viewpoint of suppressing voids, the flux composition according to this embodiment preferably contains a hindered amine compound (E). The component (E) has a structure represented by the following general formula (E1).

[0032] [ka]

[0033] In general formula (E1), R 1 are independently a methyl group or an ethyl group, and are preferably a methyl group. X is hydrogen, an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. In component (E), the structure of the portion beyond the wavy line is not particularly limited. The number of structures represented by general formula (E1) in one molecule of component (E) is preferably 1 or more and 10 or less, and more preferably 2 or more and 4 or less.

[0034] Component (E) includes bis(2,2,6,6-tetramethyl-4-piperidyl) sebacicate, tetrakis(2,2,6,6-tetramethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate, 2,2,6,6-tetramethyl-4-piperidyl methacrylate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]ethyl]butylmalonate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacic acid, bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, 1-(methyl)-8-(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl) butane-1,2,3,4-tetracarboxylate, 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, and bis(1-undecaoxy-2,2,6,6-tetramethylpiperidin-4-yl) carbonate. These may be used alone or in combination of two or more.

[0035] From the viewpoint of suppressing voids, the blending amount of component (E) is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less, even more preferably 1% by mass or more and 7% by mass or less, and particularly preferably 1.5% by mass or more and 4% by mass or less, relative to 100% by mass of the flux composition.

[0036] [Component (F)] From the viewpoint of storage stability, the flux composition according to this embodiment preferably further contains (F) a hindered phenol-based antioxidant.

[0037] Examples of component (F) include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], ethylene bis(oxyethylene)(3-tert-butyl-4-hydroxy-5-methylbenzenepropanoate), N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxamide, and N,N'-bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl}hydrazine. Among these, ethylene bis(oxyethylene)(3-tert-butyl-4-hydroxy-5-methylbenzenepropanoate) is more preferred from the viewpoint of storage stability. These may be used alone or in combination of two or more.

[0038] The blending amount of the (F) component is preferably 0.1% by mass or more and 7% by mass or less, more preferably 1% by mass or more and 6% by mass or less, and particularly preferably 2% by mass or more and 5% by mass or less, based on 100% by mass of the flux composition. When the blending amount of the antioxidant is equal to or more than the lower limit, the solder melting property and storage stability tend to be improved, while when the blending amount is equal to or less than the upper limit, the insulating properties of the flux composition tend to be maintained.

[0039] [Other ingredients] In addition to components (A), (B), (C), (D), (E), and (F), other additives may be added to the flux composition used in this embodiment as needed. Examples of other additives include imidazole compounds, antifoaming agents, modifiers, matting agents, and foaming agents. The amount of these additives added is preferably 0.01% by mass or more and 5% by mass or less based on 100% by mass of the flux composition.

[0040] [Solder composition] Next, the solder composition according to this embodiment will be described. The solder composition according to this embodiment contains the flux composition according to this embodiment described above and the (G) solder powder described below. The 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, relative to 100% by mass of the solder composition. If the amount of the flux composition is less than 5% by mass (if the amount of the solder powder exceeds 95% by mass), there will be an insufficient amount of flux composition as a binder, making it difficult to mix the flux composition and the solder powder. On the other hand, if the amount of the flux composition is more than 35% by mass (if the amount of the solder powder is less than 65% by mass), it will be difficult to form a satisfactory solder joint when using the resulting solder composition.

[0041] [(G) component] The solder powder (G) used in this embodiment is preferably made of lead-free solder powder alone, but may also be lead-containing solder powder. 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), gold (Au), antimony (Sb), lead (Pb), indium (In), bismuth (Bi), nickel (Ni), cobalt (Co), and germanium (Ge). The solder alloy in this solder powder is preferably an alloy containing tin as a main component, and 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, lead-free solder powder refers to a powder of solder metal or alloy to which no lead is added. Although the presence of lead as an unavoidable impurity in lead-free solder powder is permitted, in this case, the amount of lead is preferably 300 ppm by mass or less.

[0042] Specific examples of alloy systems for lead-free solder powder include Sn-Ag-Cu systems, Sn-Cu systems, Sn-Ag systems, Sn-Bi systems, Sn-Ag-Bi systems, Sn-Ag-Cu-Bi systems, Sn-Ag-Cu-Ni systems, Sn-Ag-Cu-Bi-Sb systems, Sn-Ag-Bi-In systems, and Sn-Ag-Cu-Bi-In-Sb systems.

[0043] The average particle size of component (G) is usually 1 μm or more and 40 μm or less, but from the viewpoint of compatibility with electronic boards with narrow solder pad pitches, 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 using a dynamic light scattering particle size measuring device.

[0044] [Method for manufacturing solder composition] The solder composition of this embodiment can be produced by blending the above-described flux composition and the above-described (G) solder powder in the above-described predetermined ratio, and stirring and mixing them.

[0045] [Electronic board] Next, the electronic substrate according to this embodiment will be described. The electronic substrate according to this embodiment is characterized by having a soldered portion using the solder composition according to this embodiment. The electronic substrate according to this embodiment can be manufactured by mounting electronic components on an electronic substrate (such as a printed wiring board) using the solder composition. Examples of the coating device used here include a screen printer, a metal mask printer, a dispenser, and a jet dispenser. Furthermore, electronic components can be mounted on an electronic board by a reflow process in which an electronic component is placed on the solder composition applied by an application device and heated under predetermined conditions in a reflow furnace to mount the electronic component on a printed wiring board.

[0046] In the reflow process, an electronic component is placed on the solder composition and heated in a reflow furnace under predetermined conditions. This reflow process allows for a sufficient solder bond 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 set appropriately depending on the melting point of the solder. For example, the preheat temperature is preferably 140°C or higher and 200°C or lower, and more preferably 150°C or higher and 160°C or lower. The preheat time is preferably 60 seconds or higher and 120 seconds or lower. The peak temperature is preferably 230°C or higher and 270°C or lower, and more preferably 240°C or higher and 255°C or lower. Furthermore, the holding time at a temperature of 220°C or higher is preferably 20 seconds or higher and 60 seconds or lower.

[0047] Furthermore, the flux composition, solder composition, and electronic substrate according to the present embodiment are not limited to the above-described embodiment, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. For example, in the electronic substrate, the printed wiring board and electronic components are bonded by a reflow process, but this is not limiting. For example, instead of the reflow process, the printed wiring board and electronic components may be bonded by a process of heating the solder composition using laser light (laser heating process). In this case, the laser light source is not particularly limited and can be appropriately selected depending on the wavelength that matches the absorption band of the metal. Examples of laser light sources include solid-state lasers (ruby, glass, YAG, etc.), semiconductor lasers (GaAs, InGaAsP, etc.), liquid lasers (dye, etc.), and gas lasers (He-Ne, Ar, CO2, excimer, etc.). [Example]

[0048] The present invention will now be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. The materials used in the examples and comparative examples are listed below. (Component (A)) Rosin resin A: Acrylic acid-modified hydrogenated rosin, product name "Pine Crystal KE-604", manufactured by Arakawa Chemical Industries, Ltd. Rosin resin B: Fully hydrogenated rosin, trade name "Foral AXE", manufactured by Eastman Chemical Company ((B1) component) Dicarboxylic acid A: Dodecanedioic acid Dicarboxylic acid B: Adipic acid ((B2) component) Amine surfactant: 2-phenylimidazoline ((C1) component) Solvent A: Diethylene glycol mono 2-ethylhexyl ether (boiling point 272°C, viscosity 11.8 mPa·s), trade name "EHDG", manufactured by Nippon Nyukazai Co., Ltd. ((C2) component) Solvent B: 1,2-butanediol (resistance 65 MΩ) Solvent C: 1,2-pentanediol (resistance 70 MΩ) Solvent D: 1,2-hexanediol (resistance 70MΩ) ((C3) component) Solvent E: Diethylene glycol dibutyl ether (boiling point 256°C, viscosity 2.4 mPa·s) ((C4) component) Solvent F: 1,4-butanediol (resistance 50MΩ) Solvent G: 1,3-butanediol (resistance 36 MΩ) Solvent H: 1,5-pentanediol (resistance 50MΩ) Solvent I: 2,4-pentanediol (resistance cannot be measured because it is a solid) Solvent J: 1,6-hexanediol (resistance cannot be measured because it is a solid) Solvent K: 1,2,4-butanetriol (resistance 20MΩ) ((D) component) Thixotropic agent A: Higher fatty acid polyamide, trade name "Tallen VA-79", manufactured by Kyoeisha Chemical Co., Ltd. Thixotropic agent B: fatty acid amide, product name "Slipax H", manufactured by Nippon Kasei Co., Ltd. Thixotropic agent C: fatty acid amide, trade name "Slipax ZHH", manufactured by Nippon Kasei Co., Ltd. Thixotropic agent D: Trade name "Himakou", manufactured by KF Trading Co., Ltd. ((E) component) Hindered amine compound: bis(1,2,2,6,6-pentamethyl-4-piperidyl)-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]ethyl]butylmalonate, trade name "Tinuvin 144", manufactured by BASF (Component (F)) Antioxidant A: bis(3-tert-butyl-4-hydroxy-5-methylbenzenepropanoate) ethylene bis(oxyethylene), trade name "Irganox 245", manufactured by BASF Antioxidant B: Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], trade name "ANOX20", manufactured by SI Group Antioxidant C: N,N'-bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl}hydrazine, trade name "Irganox MD1024", manufactured by BASF ((G) component) Solder powder: alloy composition Sn-3.0Ag-0.5Cu, particle size distribution 15-25μm

[0049] [Example 1] 28.5 mass% of rosin-based resin A, 14.5 mass% of rosin-based resin B, 5 mass% of dicarboxylic acid A, 3 mass% of dicarboxylic acid B, 5 mass% of amine-based activator, 2 mass% of antioxidant A, 23 mass% of solvent A, 9 mass% of solvent B, 4.5 mass% of solvent E, and 5.5 mass% of thixotropic agent A were charged into a container and mixed using a planetary mixer to obtain a flux composition. Thereafter, 11.5 mass % of the obtained flux composition and 88.5 mass % of the solder powder (total 100 mass %) were placed in a container and mixed with a planetary mixer to prepare a solder composition.

[0050] [Examples 2 to 13] A solder composition was obtained in the same manner as in Example 1, except that the materials were mixed according to the composition shown in Table 1. [Comparative Examples 1 to 8] A solder composition was obtained in the same manner as in Example 1, except that the materials were mixed according to the composition shown in Table 1.

[0051] <Evaluation of solder composition> The solder compositions were evaluated (void area ratio, storage stability) by the following methods. The results are shown in Table 1. (1) Void area ratio A solder composition was printed on a substrate capable of mounting QFN components, and a Sn-plated QFN (6 mm x 6 mm) was mounted on it. The solder composition was melted and soldered in a reflow oven (manufactured by Tamura Corporation) to obtain an evaluation board. The reflow conditions were a preheat temperature of 130 to 180°C (approximately 80 seconds), a time at 220°C or higher for approximately 50 seconds, a peak temperature of 248°C, and air. An X-ray photograph was taken of the bonded portion of the evaluation substrate, and the void area ratio of the lower electrode portion [(void area ÷ land area) × 100] (unit: %) was measured. The void area ratio was then calculated and evaluated according to the following criteria. A: The void area ratio is less than 10%. ◯: The void area ratio is 10% or more and less than 20%. △: The void area ratio is 20% or more and less than 30%. ×: The void area ratio is 30% or more. (2) Storage stability A solder composition was used as a sample, and a stability test was performed by storing the sample in (i) a 30°C thermostatic chamber and (ii) a 40°C thermostatic chamber for 30 days. The viscosity of the sample was measured before and after the stability test. The difference (η2-η1) between the initial viscosity value (η1) and the viscosity value (η2) after the stability test was calculated, and the viscosity change rate [{(η2-η1) / η1}×100] (unit: %) was calculated. The viscosity was measured using a spiral viscosity measurement device (PCU-II model, manufactured by Malcom Co., Ltd., measurement temperature: 25°C, rotation speed: 10 rpm, after 3 minutes of stirring). The appearance of the sample after the stability test was also observed. The storage stability was evaluated according to the following criteria. ⊚: The viscosity change rate is -15% or more and 15% or less. ◯: The viscosity change rate is −25% or more and less than −15%, or more than 15% and 25% or less. △: The viscosity change rate is −50% or more and less than −25%, or more than 25% and 50% or less. ×: The viscosity change rate is less than −50% or more than 50%, or the appearance of the sample after the stability test is dull and gritty.

[0052] [Table 1]

[0053] As is clear from the results shown in Table 1, it was confirmed that the solder compositions of the present invention (Examples 1 to 13) were excellent in both void area ratio and storage stability. Therefore, it was confirmed that the solder composition of the present invention can sufficiently suppress voids and has excellent storage stability. [Industrial Applicability]

[0054] The flux composition and solder composition of the present invention can be suitably used as a technique for mounting electronic components on electronic substrates such as printed wiring boards of electronic devices.

Claims

1. A flux composition comprising: (A) a resin; (B) an activator; (C) a solvent; (D) a thixotropic agent; and (F) a hindered phenol-based antioxidant; The component (B) contains (B1) a dicarboxylic acid having 6 or more carbon atoms, the component (C) contains (C1) a solvent having a boiling point of more than 250°C and a viscosity at 20°C of more than 10 mPa s, (C2) a diol solvent having a boiling point of 250°C or less, a resistance value of 60 MΩ or more and 80 MΩ or less, and two hydroxy groups in one molecule, and (C3) a solvent having a boiling point of 210°C or more and 275°C or less and a viscosity at 20°C of 10 mPa s or less, The component (C) does not contain a diol solvent other than the component (C2), the blending amount of the component (A) is 25% by mass or more and 60% by mass or less with respect to 100% by mass of the flux composition, the blending amount of the (B) component is 1% by mass or more and 20% by mass or less with respect to 100% by mass of the flux composition, the blending amount of the component (C) is 20% by mass or more and 60% by mass or less with respect to 100% by mass of the flux composition, the blending amount of the (D) component is 2% by mass or more and 20% by mass or less with respect to 100% by mass of the flux composition, the blending amount of the (F) component is 0.1 mass % or more and 7 mass % or less with respect to 100 mass % of the flux composition, the blending amount of the (B1) component is 0.1 mass % or more and 15 mass % or less with respect to 100 mass % of the flux composition, the blending amount of the component (C1) is 40% by mass or more and 85% by mass or less, relative to 100% by mass of the component (C); the blending amount of the component (C2) is 10% by mass or more and 50% by mass or less, relative to 100% by mass of the component (C), the blending amount of the component (C3) is 5% by mass or more and 30% by mass or less, relative to 100% by mass of the component (C); the mass ratio ((C2) / (C3)) of the component (C2) to the component (C3) is 1 / 2 or more and 6 or less; Flux composition.

2. 2. The flux composition according to claim 1, The component (C1) is diethylene glycol mono-2-ethylhexyl ether. Flux composition.

3. The flux composition according to claim 1 or 2, further containing (E) a hindered amine compound, The blending amount of the component (E) is 0.1 mass % or more and 20 mass % or less with respect to 100 mass % of the flux composition. Flux composition.

4. A flux composition according to claim 1 or 2, and (G) a solder powder, Solder composition.

5. A soldered portion using the solder composition according to claim 4. Electronic board.

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