JP2024137336A - Flux composition, solder composition, and electronic board - Google Patents

Abstract

[Problem] To provide a flux composition that can sufficiently suppress voids and improve printability. [Solution] A flux composition containing (A) a resin, (B) an activator, and (C) a solvent, wherein 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 and having a hydroxy group at each of the 1st and 2nd positions, 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. [Selected Figures] None

Description

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

The solder composition is a mixture of solder powder and a flux composition (rosin resin, activator, solvent, etc.) kneaded into a paste (see, for example, Patent Document 1). This solder composition is required to have solderability such as solder meltability and the property that solder easily wets and spreads (solder wettability), as well as void suppression, printability, etc.
On the other hand, due to the diversification of functions of electronic devices, large electronic components are being mounted on electronic boards. In addition, among the large electronic components, there are electronic components with large electrode terminal areas (e.g., QFN (Quad Flatpack No Lead), power transistors). In such electronic components, the printing area of the solder composition is large, so voids tend to occur easily.

Patent No. 5756067

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 relatively low boiling points, so the solder composition tends to become highly viscous when in use. As a result, the solder composition tends to adhere to the wall surface of the metal mask during rolling, which tends to reduce continuous printability and printability after being left on the plate.

The present invention aims to provide a flux composition, a solder composition, and an electronic board that can sufficiently suppress voids and improve printability.

According to the present invention, there are provided a flux composition, a solder composition, and an electronic board as described below.
[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, (C2) a diol solvent having a boiling point of 250° C. or less and having a hydroxy group at each of the 1- and 2-positions, 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.
Flux composition.
[2] 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 (C1) is diethylene glycol mono 2-ethylhexyl ether.
Flux composition.
[4] The flux composition according to any one of [1] to [3],
Further, (D) a thixotropic agent is contained,
The component (D) contains an amide.
Flux composition.
[5] The flux composition according to any one of [1] to [4],
Further, the composition contains (E) a hindered amine compound,
Flux composition.
[6] A flux composition according to any one of [1] to [5] and (F) a solder powder.
Solder composition.
[7] A soldered portion using the solder composition according to [6].
Electronic board.

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 improve printability.

[Flux composition]
First, the flux composition according to the present embodiment will be described. The flux composition according to the present embodiment is a component other than the solder powder in the solder composition, and contains (A) a resin, (B) an activator, and (C) a solvent, which will be described below. In addition, it is necessary for the (C) component to contain (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-based solvent having a boiling point of 250°C or less and having hydroxy groups at the 1st and 2nd positions, 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 reason why the flux composition according to the present embodiment can sufficiently suppress voids and improve printability is not necessarily clear, but the present inventors speculate as follows.
That is, in the flux composition of the present invention, as the (C) solvent, a diol-based solvent (C2) having a boiling point of 250° C. or less and having hydroxyl groups at the 1st and 2nd positions is used. A part of the (C2) component volatilizes and becomes a gas before or when the solder melts, and this gas has the effect of pushing the gas in the solder composition to the outside. And, since the solder composition containing the (C2) component that has not volatilized has a certain degree of fluidity even when the solder melts, the gas in the solder composition is gradually collected and released to the outside. In this way, voids can be sufficiently suppressed. Also, among diol-based solvents, this (C2) component tends to have a low viscosity at room temperature. And, in the flux composition of the present invention, as the (C) solvent, a solvent (C3) having a boiling point of 210° C. or more and 275° C. or less and a viscosity of 10 mPa·s or less at 20° C. is used in combination, and this makes it possible to suppress the viscosity change during use of the solder composition. In this way, the printability can be improved. The inventors presume that the effects of the present invention are achieved in the above manner.

[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 or acrylic resins are preferred from the viewpoint of viscosity stability and the like.
Examples of the rosin-based resin include rosins and rosin-based modified resins. Examples of the rosins include gum rosin, wood rosin, and tall oil rosin. Examples of the rosin-based modified resin include disproportionated rosin, polymerized rosin, hydrogenated rosin, and derivatives thereof. Examples of the hydrogenated rosin include fully hydrogenated rosin, partially hydrogenated rosin, and hydrogenated products of unsaturated organic acid-modified rosins (also called "hydrogenated acid-modified rosin"), which are modified rosins of unsaturated organic acids (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 aromatic rings such as cinnamic acid). These rosin-based resins may be used alone or in combination of two or more. Among these rosin-based resins, it is preferable to use fully hydrogenated rosin and hydrogenated acid-modified rosin, and it is more preferable to use fully hydrogenated rosin and hydrogenated acid-modified rosin in combination.
The acrylic resin is 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 in that they can prevent cracks from occurring in the flux residue even in an environment with a large temperature difference and large thermal shock. Among these acrylic resins, acrylic resins obtained by polymerizing monomers containing methacrylic acid and a monomer having an alkyl group with 2 to 6 carbon atoms, and further acrylic resins obtained by polymerizing monomers containing methacrylic acid and a monomer having an alkyl group with 2 carbon atoms are preferred. Such acrylic resins are preferred in that they suppress the stickiness of the flux residue (flux solidified product) formed and have a good crack suppression effect.

The amount of component (A) is preferably 25% by mass or more and 60% by mass or less, and more preferably 30% by mass or more and 50% by mass or less, relative to 100% by mass of the flux composition. If the amount of component (A) is equal to or more than 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. Also, if the amount of component (A) is equal to or less than the upper limit, the amount of flux residue can be sufficiently suppressed.

[Component (B)]
The activator (B) used in this embodiment preferably contains a dicarboxylic acid (B1) having 6 or more carbon atoms. This component (B1) can improve the 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.

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

The component (B) may further contain an amine-based activator (B2), which can further improve the 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, etc.), amine salts (organic acid salts or inorganic acid salts of amines such as trimethylolamine, cyclohexylamine, diethylamine, and aminoalcohols (hydrochloric acid, sulfuric acid, hydrobromic acid, etc.)), amino acids (glycine, alanine, aspartic acid, glutamic acid, valine, etc.), and amide compounds. Among these, imidazolines are preferred from the viewpoint of activity.

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

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, it is more preferable to use picolinic acid.

When the (B3) component is used, its amount is preferably 0.1% by mass or more and 8% by mass or less, more preferably 0.2% by mass or more and 5% by mass or less, and particularly preferably 0.3% by mass or more and 3% by mass or less, relative to 100% by mass of the flux composition. If the amount of the (B3) component 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.

In addition to the components (B1) to (B3), the component (B) may further contain another activator (hereinafter also referred to as the component (B4)) to the extent that the object of the present invention can be achieved. Examples of the component (B4) include halogen-based activators.

The 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, relative to 100% by mass of the flux composition. If the amount of component (B) is equal to or more than the lower limit, the activation action tends to be improved, while if the amount is equal to or less than the upper limit, the insulating properties of the flux composition tend to be maintained.

[Component (C)]
The (C) solvent used in this embodiment is required to contain (C1) a solvent having a boiling point of more than 250° C. and a viscosity of more than 10 mPa·s at 20° C. Such component (C1) is the main solvent, which allows the viscosity of the solder composition to be within an appropriate range during printing and after reflow.
Examples of the (C1) component include diethylene glycol mono 2-ethylhexyl ether (boiling point 272°C, viscosity 11.8 mPa·s) and polyethylene glycol monomethyl ether (boiling point 290 to 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.

The 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).

The (C) solvent used in this embodiment is required to contain (C2) a diol-based solvent having a boiling point of 250° C. or less and having a hydroxy group at each of positions 1 and 2. Such a (C2) component has a high effect of suppressing voids and has little adverse effect on printability.
Examples of the (C2) component include 1,2-butanediol, 1,2-pentanediol, and 1,2-hexanediol. Among these, 1,2-butanediol is preferred from the viewpoint of printability. These may be used alone or in combination of two or more.

The amount of the (C2) component is preferably 10% by mass or more and 50% by mass or less, more preferably 15% by mass or more and 45% by mass or less, and particularly preferably 20% by mass or more and 40% by mass or less, relative to 100% by mass of the (C) component. If the amount of the (C2) component is equal to or more than the lower limit, the effect of suppressing voids can be further enhanced. On the other hand, if the amount of the (C2) component is equal to or less than the upper limit, adverse effects on printability can be suppressed.

The (C) solvent used in this embodiment is required to contain (C3) a solvent having a boiling point of 210° C. or more and 275° C. or less and a viscosity of 10 mPa·s or less at 20° C. Such a (C3) component can improve printability.
Examples of the (C3) component 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). The viscosity in parentheses is the viscosity at 20°C.

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.

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.

The (C) component may contain a solvent other than the (C1), (C2) and (C3) components (hereinafter also referred to as the (C4) component). As the (C4) component, a known solvent can be appropriately used. As such a solvent, it is preferable to use a solvent having a boiling point of 170°C or more and 250°C or less.
Examples of such a solvent include hexylene glycol (boiling point 197° C.) and methyl carbitol (boiling point 194° C.). These may be used alone or in combination of two or more.
From the viewpoint of printability, it is preferable not to use a diol solvent other than the component (C2) as the component (C).

The amount of component (C) is preferably 20% by mass or more and 60% by mass or less, and more preferably 30% by mass or more and 50% by mass or less, relative to 100% by mass of the flux composition. If the amount of the solvent is within the above range, the viscosity of the resulting solder composition can be appropriately adjusted to an appropriate range.

[Component (D)]
The flux composition according to the present embodiment preferably contains (D) a thixotropic agent from the viewpoint of suppressing sagging during printing or heating. As the (D) component, a known thixotropic agent can be appropriately used. Examples of the thixotropic agent used here include hardened castor oil, amides, kaolin, colloidal silica, organic bentonite, and glass frit. Among these, amides are preferred from the viewpoint of suppressing sagging. These may be used alone or in combination of two or more.

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 equal to or more than the lower limit, sufficient thixotropy is obtained and sagging tends to be suppressed. On the other hand, if the blending amount is equal to or less than the upper limit, the thixotropy is not too high and printing defects are less likely to occur.

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

In formula (E1), R ¹ is independently a methyl group or an ethyl group, and is 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 addition, 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 the component (E) is preferably 1 or more and 10 or less, and more preferably 2 or more and 4 or less.

(E) component includes bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, 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)sebacate, cate, 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.

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.

[Antioxidants]
From the viewpoint of solder melting property, the flux composition according to the present embodiment preferably further contains an antioxidant. As the antioxidant used here, a known antioxidant can be appropriately used. Examples of the antioxidant include sulfur compounds, hindered phenol compounds, and phosphite compounds. Among these, hindered phenol compounds are preferred.

Examples of hindered phenol compounds include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], bis(3-tert-butyl-4-hydroxy-5-methylbenzenepropanoate)ethylene bis(oxyethylene), 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. These may be used alone or in combination of two or more.

When an antioxidant is used, the amount of the antioxidant is preferably 0.1% by mass or more and 5% by mass or less, based on 100% by mass of the flux composition. If the amount of the antioxidant is equal to or more than the lower limit, the solder melting property tends to be improved, while if the amount is equal to or less than the upper limit, the insulating properties of the flux composition tend to be maintained.

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

[Solder Composition]
Next, the solder composition according to the present embodiment will be described. The solder composition according to the present embodiment contains the flux composition according to the present embodiment described above and the solder powder (F) 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. When the amount of the flux composition is less than 5% by mass (when the amount of the solder powder exceeds 95% by mass), the flux composition as a binder is insufficient, so that it tends to be difficult to mix the flux composition and the solder powder. On the other hand, when the amount of the flux composition is more than 35% by mass (when the amount of the solder powder is less than 65% by mass), when the obtained solder composition is used, it tends to be difficult to form a sufficient solder joint.

[Component (F)]
The solder powder (F) used in this embodiment is preferably made of only lead-free solder powder, but may 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 the solder powder is preferably an alloy mainly composed of tin, more preferably containing tin, silver and copper, and may further contain at least one of antimony, bismuth and nickel as an additive element.
Here, 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 permitted, but in this case, the amount of lead is preferably 300 ppm by mass or less.

Specific examples of alloy systems for 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, and Sn-Ag-Cu-Bi-In-Sb systems.

The average particle diameter of component (F) is usually 1 μm or more and 40 μm or less, but from the viewpoint of being compatible with electronic boards with narrow pitches 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 diameter can be measured by a dynamic light scattering type particle diameter measuring device.

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

[Electronic board]
Next, the electronic board according to the present embodiment will be described. The electronic board according to the present embodiment is characterized by having a soldered portion using the solder composition according to the present embodiment. The electronic board according to the present embodiment can be manufactured by mounting electronic components on an electronic board (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.
In addition, electronic components can be mounted on an electronic board by a reflow process in which electronic components are placed on the solder composition applied by an application device and heated under specified conditions in a reflow furnace to mount the electronic components on a printed wiring board.

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 a sufficient solder joint to be formed 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 140° C. or more and 200° C. or less, and more preferably 150° C. or more and 160° C. or less. The preheat time is preferably 60 seconds or more and 120 seconds or less. The peak temperature is preferably 230° C. or more and 270° C. or less, and more preferably 240° C. or more and 255° C. or less. The holding time at a temperature of 220° C. or more is preferably 20 seconds or more and 60 seconds or less.

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

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 shown below.
(Component (A))
Rosin-based resin A: acrylic acid-modified hydrogenated rosin, trade name "Pine Crystal KE-604", manufactured by Arakawa Chemical Industries, Ltd. Rosin-based resin B: fully hydrogenated rosin, trade name "Foral AXE", manufactured by Eastman Chemical Co. (component (B1))
Dicarboxylic acid A: dodecanedioic acid Dicarboxylic acid B: adipic acid (component (B2))
Amine-based surfactant: 2-phenylimidazoline (component (C1))
Solvent A: Diethylene glycol mono 2-ethylhexyl ether (boiling point 272°C, viscosity 11.8 mPa·s), product name "EHDG", manufactured by Nippon Nyukazai Co., Ltd. (component (C2))
Solvent B: 1,2-butanediol Solvent C: 1,2-pentanediol Solvent D: 1,2-hexanediol (component (C3))
Solvent E: Diethylene glycol dibutyl ether (boiling point 256° C., viscosity 2.4 mPa·s)
Solvent F: Diethylene glycol butyl methyl ether (boiling point 212°C, viscosity 1.6 mPa·s)
Solvent G: Tetraethylene glycol dimethyl ether (boiling point 275°C, viscosity 3.8 mPa·s)
Solvent H: Diethylene glycol monobutyl ether (boiling point 230° C., viscosity 5.85 mPa·s)
Solvent I: Diethylene glycol monobutyl ether acetate (boiling point 247° C., viscosity 3.56 mPa·s)
(Component (C4))
Solvent J: 1,4-butanediol Solvent K: 1,3-butanediol Solvent L: 1,5-pentanediol Solvent M: 2,4-pentanediol Solvent N: 1,6-hexanediol Solvent O: 1,2,4-butanetriol (Component (D))
Thixotropic agent: higher fatty acid polyamide, trade name "Talen VA-79", manufactured by Kyoeisha Chemical Co., Ltd. (component (E))
Hindered amine compound: bis(1,2,2,6,6-pentamethyl-4-piperidyl)-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]ethyl]butyl malonate, trade name "Tinuvin 144", manufactured by BASF (component (F))
Solder powder: alloy composition Sn-3.0Ag-0.5Cu, particle size distribution 15-25 μm

[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, 25 mass% of solvent A, 9 mass% of solvent B, 4.5 mass% of solvent E, and 5.5 mass% of a thixotropic agent were charged into a container and mixed using a planetary mixer to obtain a flux composition.
Thereafter, 11.5% by mass of the obtained flux composition and 88.5% by mass of solder powder (total 100% by mass) were placed in a container and mixed with a planetary mixer to prepare a solder composition.

[Examples 2 to 11]
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 9]
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.

<Evaluation of Solder Composition>
The solder compositions were evaluated (void area ratio, continuous printability, printability after being left on the plate, and viscosity change after rolling) by the following methods. The results are shown in Table 1.
(1) Void area ratio A solder composition was printed on a board capable of mounting QFN components, and a Sn-plated QFN (6 mm x 6 mm) was mounted on it. The solder composition was melted in a reflow furnace (manufactured by Tamura Corporation) and soldered to obtain an evaluation board. The reflow conditions were a preheat temperature of 130 to 180°C (about 80 seconds), a time at or above 220°C for about 50 seconds, a peak temperature of 248°C, and air.
An X-ray radiograph 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%.
A: The void area ratio is 10% or more and less than 20%.
Δ: The void area ratio is 20% or more and less than 30%.
×: The void area ratio is 30% or more.
(2) Continuous Printability The solder composition was put into a printer, and 10 sheets were continuously printed without cleaning under the conditions of a mask thickness of 0.08 mm, a squeegee speed of 50 mm/s, a printing pressure of 20 mm×N, and a plate release speed of 2 mm/s. 100 points each with a diameter of 0.18 mm were checked with a visual inspection machine (Kohyoung aspire 2), and the continuous printability was evaluated according to the following criteria.
⊚: The Min volume fraction is 60% or more.
◯: The Min volume fraction is 50% or more and less than 60%.
Δ: The Min volume fraction is more than 30% and less than 50%.
×: The minimum volume ratio is 30% or less.
(3) Printability after being left on the plate The above (2) continuous printability test was performed, and then the plate was left on the plate in an environment of a temperature of 25° C. and a relative humidity of 50% for 1 hour. After being left on the plate, the above (2) continuous printability test was performed, and 10 sheets were continuously reprinted. 100 points each with a diameter of 0.18 mm were checked with a visual inspection machine (Kohyoung aspire 2), and the printability after being left on the plate was evaluated according to the following criteria.
⊚: The number of printed sheets when the minimum volume ratio recovered to 50% was the first sheet.
◯: The number of printed sheets when the minimum volume ratio recovered to 50% was 2.
Δ: The number of printed sheets when the minimum volume ratio recovered to 50% was 3.
x: The number of printed sheets at which the minimum volume ratio recovered to 50% was 4 or more.
(4) Viscosity change after rolling The solder composition is used as a sample, and this sample is placed on a metal mask without an opening. This is set in a printing machine, and a rolling test is performed in which continuous printing is performed with a urethane squeegee for 12 hours. The viscosity of the sample before and after the rolling test is measured. The difference (η2-η1) between the initial viscosity value (η1) and the viscosity value after the rolling test (η2) is calculated, and the viscosity change rate [{(η2-η1)/η1}×100] (unit: %) is calculated. The viscosity measurement was performed using a spiral type viscosity measurement (PCU-II type, manufactured by Malcom Co., Ltd., measurement temperature: 25°C, rotation speed: 10 rpm, after stirring for 3 minutes). The viscosity change after rolling was evaluated according to the following criteria.
⊚: The viscosity change rate is −10% or more and 10% or less.
◯: The rate of change in viscosity is −20% or more and less than −10%, or more than 10% and 20% or less.
Δ: The rate of change in viscosity is −30% or more and less than −20%, or more than 20% and 30% or less.
×: The viscosity change rate is less than −30% or more than 30%.

As is clear from the results shown in Table 1, it was confirmed that the solder compositions of the present invention (Examples 1 to 11) were good in all respects of void area ratio, continuous printability, printability after being left on the plate, and viscosity change after rolling.
Therefore, it was confirmed that the solder composition of the present invention can sufficiently suppress voids and improve printability.

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 for electronic devices.

Claims (7)

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, (C2) a diol solvent having a boiling point of 250° C. or less and having a hydroxy group at each of the 1- and 2-positions, 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.
Flux composition. 2. The flux composition according to claim 1,
The component (B) contains (B1) a dicarboxylic acid having 6 or more carbon atoms.
Flux composition. The flux composition according to claim 1 or 2,
The component (C1) is diethylene glycol mono 2-ethylhexyl ether.
Flux composition. The flux composition according to claim 1 or 2,
Further, (D) a thixotropic agent is contained,
The component (D) contains an amide.
Flux composition. The flux composition according to claim 1 or 2,
Further, the composition contains (E) a hindered amine compound,
Flux composition. A flux composition according to claim 1 or 2, and (F) a solder powder.
Solder composition. A soldered portion comprising the solder composition according to claim 6.
Electronic board.