JP6895213B2 - Method for manufacturing solder composition and electronic board - Google Patents

Description

The present invention relates to solder compositions and electronic substrates.

The solder composition is a mixture obtained by kneading a flux composition (rosin-based resin, activator, solvent, etc.) with solder powder to form a paste (for example, Patent Document 1). In this solder composition, in addition to solderability such as solder meltability and the property that the solder easily wets and spreads (solder wet spread), void suppression and printability are required.
Further, by using this solder composition, a solder bond can be formed between an electronic component and an electronic substrate by a reflow process. Examples of the reflow device used in this reflow process include an air reflow device, a vacuum reflow device, a formic acid reflow device, and a plasma reflow device. From the viewpoint of equipment cost, an air reflow device that performs a reflow process in an air atmosphere is preferable. Therefore, the solder composition is required to have excellent solder meltability even when the reflow process is performed in an air atmosphere.

Japanese Patent No. 5756067

However, when the reflow step is performed in an air atmosphere, the flux composition needs to contain a predetermined amount or more of the rosin-based resin from the viewpoint of removing the oxide film and maintaining the cleanliness of the copper foil surface. On the other hand, when the content of the rosin-based resin in the flux composition is high, the viscosity of the flux composition increases and voids are likely to occur. Further, from the viewpoint of suppressing voids, it is conceivable to use a solvent having a low boiling point as the solvent in the flux composition. However, when a solvent having a low boiling point is used, the solvent volatilizes during printing and the viscosity of the solder composition changes, so that the printability deteriorates. As described above, there is a trade-off relationship between void suppression and printability, and there has been no solder composition that can satisfy these at the same time.

Therefore, the present invention provides a solder composition having excellent solder meltability, sufficiently suppressing voids, and sufficient printability even when the reflow process is performed in an atmospheric atmosphere, and an electronic substrate using the same. The purpose is.

In order to solve the above problems, the present invention provides the following solder compositions and electronic substrates.
The solder composition of the present invention comprises a flux composition containing (A) a rosin resin, (B) an activator and (C) a solvent, and (D) a solder powder having a melting point of 200 ° C. or higher and 250 ° C. or lower. The component (A) contains a hydrogenated additive of (A1) unsaturated organic acid-modified rosin, and the component (C) has a (C1) melting point of 40 ° C. or higher and a boiling point of 220 ° C. or lower. The hexanediol-based solvent (C2) and the solvent having a viscosity of (C2) of 10 mPa · s or less at 20 ° C. and a boiling point of 270 ° C. or higher are contained, and the blending amount of the component (A) is the flux composition. It is characterized in that it is 30% by mass or more with respect to 100% by mass of the substance.

In the solder composition of the present invention, the component (C1) is preferably at least one selected from the group consisting of 2,5-dimethylhexane-2,5-diol and 1,6-hexanediol. ..
In the solder composition of the present invention, the component (C2) is preferably tetraethylene glycol dimethyl ether.
The electronic substrate of the present invention is characterized by including a soldering portion using the solder composition.

According to the solder composition of the present invention, the reason why the solder meltability is excellent, voids can be sufficiently suppressed, and sufficient printability is obtained even when the reflow process is performed in an air atmosphere is not necessarily clear, but the present invention. Those infer as follows.
That is, in the solder composition of the present invention, (A1) a hydrogenated additive of unsaturated organic acid-modified rosin is used as the (A) rosin-based resin, and the blending amount of the component (A) is set to a predetermined amount or more. .. Therefore, even when the reflow process is performed in an air atmosphere, the oxide film can be removed, the cleanliness of the copper foil surface can be maintained, and sufficient solder meltability can be ensured. Further, in the solder composition of the present invention, as the (C) solvent, (C1) a hexanediol-based solvent having a melting point of 40 ° C. or higher and a boiling point of 220 ° C. or lower, and (C2) a viscosity at 20 ° C. A solvent having a boiling point of 10 mPa · s or less and a boiling point of 270 ° C. or more is used in combination. Since the component (C1) has a relatively low boiling point, it volatilizes before the solder melts or when the solder melts and becomes a gas, but this gas has the effect of pushing the gas in the solder composition to the outside. is there. Since the component (C2) has a high boiling point, it hardly volatilizes even when the solder is melted. Therefore, the generation of voids due to the vaporization of the solvent can be suppressed. Further, since the solder composition containing the component (C2) has a certain degree of fluidity even when the solder is melted, the gas in the solder composition is gradually collected and released to the outside. In this way, voids can be sufficiently suppressed. Further, neither the component (C1) nor the component (C2) volatilizes at room temperature. Therefore, at the time of printing, the change in viscosity of the solder composition is small, and sufficient printability can be ensured. As described above, the present inventors presume that the above-mentioned effect of the present invention is achieved.

According to the present invention, it is possible to provide a solder composition having excellent solder meltability, sufficiently suppressing voids, and sufficient printability even when the reflow process is performed in an atmospheric atmosphere, and an electronic substrate using the same. ..

The solder composition of the present invention contains the flux composition described below and the solder powder (D) described below.

[Flux composition]
First, the flux composition used in the present invention will be described. The flux composition used in the present invention is a component other than the solder powder in the solder composition, and contains (A) a rosin-based resin, (B) an activator, and (C) a solvent.

[(A) component]
Examples of the (A) rosin-based resin used in the present embodiment include rosins and rosin-based modified resins. Examples of rosins include gum rosin, wood rosin and tall oil rosin. Examples of the rosin-based modified resin include unsaturated rosins, polymerized rosins, hydrogenated rosins (fully hydrogenated rosins, partially hydrogenated rosins, and unsaturated organic acids ((meth) acrylic acids and other aliphatic unsaturated monobases). An unsaturated organic that is a modified rosin of an aliphatic unsaturated dibasic acid such as α, β-unsaturated carboxylic acid such as acid, fumaric acid and maleic acid, and an unsaturated carboxylic acid having an aromatic ring such as cinnamic acid). Examples thereof include hydrogenated additives of acid-modified rosin (also referred to as "hydrogenated acid-modified rosin") and derivatives thereof. One of these rosin-based resins may be used alone, or two or more thereof may be mixed and used.

In the present embodiment, the component (A) needs to contain a hydrogenated additive of (A1) unsaturated organic acid-modified rosin. When this component (A1) is not contained, the solder meltability becomes insufficient even when the reflow step is performed in an air atmosphere.
Further, the component (A) may contain a rosin-based resin (component (A2)) other than the component (A1), if necessary. In such a case, the mass ratio of the component (A1) to the component (A) [{(A1) / (A)} × 100] is preferably 50% by mass or more, preferably 70% by mass or more. It is more preferable, and 90% by mass or more is particularly preferable.

The blending amount of the component (A) needs to be 30% by mass or more with respect to 100% by mass of the flux composition. When the blending amount of the component (A) is less than 30% by mass, the solder meltability when the reflow step is performed in an air atmosphere becomes insufficient. Further, from the viewpoint of the balance between the solder meltability and the flux residue, the blending amount of the component (A) is preferably 30% by mass or more and 70% by mass or less with respect to 100% by mass of the flux composition, and 35 It is more preferably mass% or more and 65 mass% or less, and particularly preferably 40 mass% or more and 60 mass% or less.

[(B) component]
Examples of the (B) activator used in the present embodiment include an organic acid, a non-dissociative activator composed of a non-dissociative halogenated compound, and an amine-based activator. One of these activators may be used alone, or two or more thereof may be mixed and used. Among these, from the viewpoint of environmental measures and the viewpoint of suppressing corrosion at the soldered portion, it is preferable to use an organic acid or an amine-based activator (which does not contain halogen), and an organic acid is used. Is more preferable.

Examples of the organic acid include other organic acids in addition to monocarboxylic acids and dicarboxylic acids.
Monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enant acid, capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, tubercrostearic acid , Arakidic acid, behenic acid, lignoseric acid, and glycolic acid.
Examples of the dicarboxylic acid 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, and diglycolic acid.
Other organic acids include dimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anis acid, citric acid, picolin acid and the like.

Examples of the non-dissociative activator include non-salt organic compounds in which halogen atoms are covalently bonded. The halogenated compound may be a compound formed by a covalent bond of each single element of chlorine, bromine, and fluorine, such as chlorinated compound, brominated compound, and fluoride, but any two or all of chlorine, bromine, and fluorine can be used. It may be a compound having a covalent bond of. These compounds preferably have a polar group such as a hydroxyl group or a carboxyl group, such as a halogenated alcohol or a halogenated carboxyl compound, in order to improve the solubility in an aqueous solvent. Examples of the halogenated alcohol include 2,3-dibromopropanol, 2,3-dibromobutanediol, trans-2,3-dibromo-2-butene-1,4-diol, 1,4-dibromo-2-butanol, and the like. And brominated alcohols such as tribromoneopentyl alcohols, chlorinated alcohols such as 1,3-dichloro-2-propanol and 1,4-dichloro-2-butanol, fluorinated alcohols such as 3-fluorocatechol, and Other compounds similar to these can be mentioned. The carboxylated carboxyl compounds include carboxyl compounds iodide such as 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, and 5-iodoanthranic acid, 2-chlorobenzoic acid, and Examples thereof include carboxyl chloride compounds such as 3-chloropropionic acid, brominated carboxyl compounds such as 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid, and 2-bromobenzoic acid, and other similar compounds. ..

Examples of the amine-based activator include amines (polyamines such as ethylenediamine), amine salts (amines such as trimethylolamine, cyclohexylamine, and diethylamine, and organic or inorganic acid salts such as aminoalcohol (hydrochloride, sulfuric acid). , And hydrobromic acid)), amino acids (such as glycine, alanine, aspartic acid, glutamic acid, and valine), amide compounds, and the like. Specifically, diphenylguanidine hydrobromide, cyclohexylamine hydrobromide, diethylamine salts (such as hydrochloride, succinate, adipate, and sebasinate), triethanolamine, monoethanolamine, In addition, hydrobromide of these amines and the like can be mentioned.

The blending amount of the component (B) is preferably 1% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 15% by mass or less, based on 100% by mass of the flux composition. It is particularly preferable that it is 2% by mass or more and 10% by mass or less. If the blending amount of the component (B) is less than the lower limit, solder balls tend to be generated, while if it exceeds the upper limit, the insulating property of the flux composition tends to decrease.

[(C) component]
The (C) solvent used in this embodiment is (C1) a hexanediol-based solvent having a melting point of 40 ° C. or higher and a boiling point of 220 ° C. or lower, and (C2) a viscosity at 20 ° C. of 10 mPa · s or less. It is necessary to contain a solvent having a boiling point of 270 ° C. or higher. By using the component (C1) and the component (C2) in combination, it is possible to achieve both suppression of voids and printability.
The upper limit of the melting point of the component (C1) is not particularly limited. For example, the melting point of the component (C1) may be 100 ° C. or lower. Further, the lower limit of the boiling point of the component (C1) is not particularly limited. For example, the boiling point of the component (C1) may be 120 ° C. or higher. In the present specification, the boiling point means the boiling point at 1013 hPa.

The component (C1) includes 2,5-dimethyl-2,5-hexanediol (melting point: 86 to 90 ° C., boiling point: 214 ° C.) and 1,6-hexanediol (melting point: 40 to 44 ° C., boiling point: 215 ° C.) and (2S, 5S) -2,5-hexanediol (melting point: 52 to 56 ° C., boiling point: 212 to 215 ° C.) and the like. Among these, 2,5-dimethyl-2,5-hexanediol is more preferable from the viewpoint of the melting point of the solvent. One of these may be used alone, or two or more thereof may be mixed and used.

Further, from the viewpoint of further suppressing voids, the viscosity of the component (C2) at 20 ° C. is more preferably 8 mPa · s or less, particularly preferably 5 mPa · s or less, and 2 mPa · s or less. Is most preferable. The lower limit of the viscosity of the component (C2) at 20 ° C. is not particularly limited. For example, the viscosity of the component (C2) at 20 ° C. may be 0.01 mPa · s or more. The viscosity of the solvent can be measured with a Brookfield type rotational viscometer.
Further, from the viewpoint of further suppressing voids, the boiling point of the component (C2) is more preferably 275 ° C. or higher and 300 ° C. or lower.

The components (C2) include tetraethylene glycol dimethyl ether (boiling point: 275 ° C., viscosity: 3.8 mPa · s), tripropylene glycol monobutyl ether (boiling point: 274 ° C., viscosity: 8.4 mPa · s), and maleic acid. Examples thereof include dibutyl (boiling point: 281 ° C., viscosity: 5.0 mPa · s). Among these, tetraethylene glycol dimethyl ether is more preferable from the viewpoint of the viscosity of the solvent. One of these may be used alone, or two or more thereof may be mixed and used. The viscosity described in parentheses is the viscosity at 20 ° C.

The mass ratio of the component (C2) to the component (C1) ((C2) / (C1)) is preferably 1 or more and 10 or less from the viewpoint of the balance between void suppression and printability. It is more preferably 2 or more and 8 or less, and particularly preferably 2 or more and 6 or less.

The component (C) may contain a solvent (component (C3)) other than the component (C1) and the component (C2) as long as the object of the present invention can be achieved. The component (C3) can dissolve or disperse the solid content in the solder composition. The component (C3) is preferably liquid at 20 ° C.

As the component (C3), diethylene glycol monohexyl ether (boiling point: 259 ° C., viscosity: 8.6 mPa · s), diethylene glycol monobutyl ether (boiling point: 230 ° C., viscosity: 6.6 mPa · s), α, β, γ -Tarpineol (boiling point: 217 ° C., viscosity: 67 mPa · s), benzyl glycol (boiling point: 256 ° C., viscosity: 12.6 mPa · s), diethylene glycol mono2-ethylhexyl ether (boiling point: 272 ° C., viscosity: 10.4 mPa · s) s), Tripropylene glycol (boiling point: 265 ° C., viscosity: 57.2 mPa · s), diethylene glycol monobenzyl ether (boiling point: 302 ° C., viscosity: 19.3 mPa · s), diethylene glycol dibutyl ether (boiling point: 255 ° C., viscosity) : 2.4 mPa · s), tripropylene glycol monomethyl ether (boiling point: 242 ° C., viscosity: 1 mPa · s), dipropylene glycol monobutyl ether (boiling point: 231 ° C., viscosity: 7.4 mPa · s), ethylene glycol mono 2 -Ethylhexyl ether (boiling point: 229 ° C., viscosity: 7.6 mPa · s), diethylene glycol monoethyl ether acetate (boiling point: 220 ° C., viscosity: 2.8 mPa · s) and 2,2-dimethyl-1,3-propanediol (Viscosity: 127 to 130 ° C., boiling point: 210 ° C.) and the like. One of these may be used alone, or two or more thereof may be mixed and used. The viscosity described in parentheses is the viscosity at 20 ° C.

When the component (C3) is used, the mass ratio of the component (C3) to the component (C) ((C3) / (C)) is 1/15 from the viewpoint of the balance between void suppression and printability. It is preferably 1/2 or more, more preferably 1/10 or more and 1/2 or less, and particularly preferably 1/5 or more and 1/3 or less.

The blending amount of the component (C) is preferably 20% by mass or more and 65% by mass or less, more preferably 30% by mass or more and 60% by mass or less, based on 100% by mass of the flux composition. It is particularly preferable that it is by mass% or more and 50% by mass or less. When the blending amount of the solvent is within the above range, the viscosity of the obtained solder composition can be appropriately adjusted within an appropriate range.

In the present embodiment, a thixo agent may be further contained from the viewpoint of printability and the like. Examples of the thixo agent used in the present embodiment include cured castor oil, amides, kaolin, colloidal silica, organic bentonite, and glass frit. One of these thixogens may be used alone, or two or more thereof may be mixed and used.

When the thixo agent is used, the blending amount thereof is preferably 3% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less with respect to 100% by mass of the flux composition. .. If the blending amount is less than the lower limit, the tix property is not obtained and dripping tends to occur. On the other hand, if the blending amount exceeds the upper limit, the tix property is too high and printing defects tend to occur.

[Other ingredients]
In the flux composition used in the present embodiment, in addition to the component (A), the component (B), the component (C) and the thixo agent, if necessary, other additives, and further Resin can be added. Other additives include antifoaming agents, antioxidants, modifiers, matting agents, foaming agents and the like. The blending amount of these additives is preferably 0.01% by mass or more and 5% by mass or less with respect to 100% by mass of the flux composition. Examples of other resins include acrylic resins.

[Solder composition]
Next, the solder composition of this embodiment will be described. The solder composition of the present embodiment contains the above-mentioned flux composition of the present embodiment and the solder powder (D) 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 8% by mass with respect to 100% by mass of the solder composition. It is particularly preferable that it is% or more and 12% by mass or less. 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, so the flux composition and the solder powder are mixed. 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), the obtained solder composition is used. It tends to be difficult to form a sufficient solder joint.

[(D) component]
The solder powder (D) used in this embodiment is a solder powder having a melting point of 200 ° C. or higher and 250 ° C. or lower. In this embodiment, the boiling points of the component (C1) and the component (C2) are defined on the premise that a solder powder having a melting point of 200 ° C. or higher and 250 ° C. or lower is used.
As the solder alloy in this solder powder, an alloy containing tin (Sn) as a main component is preferable. Examples of the second element of this alloy include silver (Ag), copper (Cu), zinc (Zn), bismuth (Bi), indium (In) and antimony (Sb). Further, other elements (third element and later) may be added to this alloy as needed. Other elements include copper, silver, bismuth, indium, antimony, aluminum (Al) and the like.
Here, the lead-free solder powder refers to a solder metal or alloy powder to which lead is not added. However, it is permissible for lead to be present as an unavoidable impurity in the lead-free solder powder, but in this case, the amount of lead is preferably 300 mass ppm or less.

Specific examples of the solder alloy in the lead-free solder powder include Sn-Ag type and Sn-Ag-Cu type. Among these, Sn-Ag-Cu based solder alloys are preferably used from the viewpoint of the strength of the solder joint. The melting point of the Sn—Ag—Cu-based solder is usually 200 ° C. or higher and 250 ° C. or lower (preferably 200 ° C. or higher and 240 ° C. or lower). Among the Sn—Ag—Cu type solders, the solder having a low silver content has a melting point of 210 ° C. or higher and 250 ° C. or lower (preferably 220 ° C. or higher and 240 ° C. or lower).

The average particle size of the component (D) is usually 1 μm or more and 40 μm or less, but it is more preferably 1 μm or more and 35 μm or less from the viewpoint of supporting an electronic substrate having a narrow solder pad pitch, and 2 μm or more. It is even more preferably 30 μm or less, and particularly preferably 3 μm or more and 20 μm or less. The average particle size can be measured by a dynamic light scattering type particle size measuring device.

[Manufacturing method of solder composition]
The solder composition of the present embodiment can be produced by blending the flux composition described above and the solder powder (D) described above in the above-mentioned predetermined ratios and stirring and mixing them.

[Electronic substrate]
Next, the electronic substrate of this 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 board of the present invention can be manufactured by mounting an electronic component on an electronic board (printed wiring board or the like) using the solder composition.
The solder composition of the present embodiment described above can sufficiently suppress voids having a large diameter even when the printed area of the solder composition is large. Therefore, as the electronic component, an electronic component having a large electrode terminal area (for example, a power transistor) may be used. The printed area of the solder composition may be, for example, 20 mm ² or more, 30 mm ² or more, ^{or 40 mm 2} or more. The printed area corresponds to the area of the electrode terminals of the electronic component.
Examples of the coating apparatus used here include a screen printing machine, a metal mask printing machine, a dispenser, and a jet dispenser.
Further, the electronic components are placed on the solder composition coated by the coating device, heated by a reflow furnace under predetermined conditions, and the electronic components are mounted on the printed wiring board by a reflow process. Can be implemented in.

In the reflow step, the electronic component is placed on the solder composition and heated by a reflow furnace under predetermined conditions. By this reflow process, sufficient solder bonding can be performed 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 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 more and 120 seconds or less. 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. The holding time of the temperature of 220 ° C. or higher is preferably 20 seconds or longer and 60 seconds or shorter.

Further, the solder composition and the electronic substrate of the present embodiment are not limited to the above-described embodiment, and modifications and improvements within the range in which the object of the present invention can be achieved are included in the present invention.
For example, in the electronic board, the printed wiring board and the electronic component are bonded by the reflow process, but the present invention is not limited to this. For example, instead of the reflow step, the printed wiring board and the electronic component may be adhered by a step of heating the solder composition using a laser beam (laser heating step). In this case, the laser light source is not particularly limited, and can be appropriately adopted according to the wavelength matched to the absorption band of the metal. Laser sources include, for example, solid-state lasers (ruby, glass, YAG, etc.), semiconductor lasers (GaAs, and InGaAsP, etc.), liquid lasers (dye, etc.), and gas lasers (He-Ne, Ar, CO ₂ , and so on). Eximer etc.).

Next, the present invention will 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 Examples and Comparative Examples are shown below.
((A1) component)
Rosin-based resin A: Hydrophobic acid-modified rosin, trade name "Pine Crystal KE-604", manufactured by Arakawa Chemical Industry Co., Ltd. Rosin-based resin B: polymerized rosin, trade name "China Polymerized Rosin 140", manufactured by Arakawa Chemical Industry Co., Ltd. B) Ingredients)
Activator A: Suberic acid Activator B: Dibromobutenediol, manufactured by Air Brown ((C1) component)
Solvent A: 2,5-dimethyl-2,5-hexanediol (melting point: 86-90 ° C, boiling point: 214 ° C)
Solvent B: 1,6-hexanediol (melting point: 40-44 ° C, boiling point: 215 ° C)
((C2) component)
Solvent C: Tetraethylene glycol dimethyl ether (boiling point: 275 ° C., viscosity: 3.8 mPa · s), trade name "High Solve MTEM", Toho Chemical Industry Solvent D: tripropylene glycol monobutyl ether (boiling point: 274 ° C., viscosity: 8) .4mPa · s)
((C3) component)
Solvent E: Diethylene glycol monohexyl ether (boiling point: 259 ° C., viscosity: 8.6 mPa · s)
Solvent F: 2,2-dimethyl-1,3-propanediol (melting point: 127 to 130 ° C, boiling point: 210 ° C)
Solvent G: Diethylene glycol monobutyl ether (boiling point: 230 ° C., viscosity: 6.6 mPa · s)
Solvent H: α, β, γ-turpineol (boiling point: 217 ° C., viscosity: 67 mPa · s), trade name “tarpineol C”, manufactured by Nippon Terpene Chemical Co., Ltd. ((D) component)
Solder powder: Alloy composition is Sn-3.0Ag-0.5Cu, particle size distribution is 20 to 38 μm, solder melting point is 217 to 220 ° C.
(Other ingredients)
Tixo agent: Hardened castor oil, trade name "Himakou", KF Trading's antioxidant: Trade name "Irganox 245", BASF's

[Example 1]
Rosin resin A 40% by mass, activator A2% by mass, activator B2% by mass, solvent A5% by mass, solvent C26.5% by mass, solvent E14.5% by mass, thixo agent 6% by mass and antioxidant 4% by mass Was put into a container and mixed using a planetary mixer to obtain a flux composition.
Then, 11% by mass of the obtained flux composition and 89% by mass of the solder powder (100% by mass in total) were put into a container and mixed with a planetary mixer to prepare a solder composition.

[Examples 2 to 5]
A solder composition was obtained in the same manner as in Example 1 except that each material was blended according to the composition shown in Table 1.
[Comparative Examples 1 to 11]
A solder composition was obtained in the same manner as in Example 1 except that each material was blended according to the composition shown in Table 1.

<Evaluation of solder composition>
Evaluation of the solder composition (void, printability, solder meltability, adhesiveness, viscosity change during continuous printing, copper plate corrosion) was carried out by the following methods. The results obtained are shown in Table 1.
(1) Void power transistor (size: 5.5 mm x 6.5 mm, thickness: 2.3 mm, land: tin plating, land area: 30 mm ² ) and QFN (size: 6 mm x 6 mm, land: tin plating) , Land area: 36 mm ² ) The solder composition was printed on a substrate having electrodes capable of mounting the solder composition using a metal mask (thickness: 0.13 mm) having a corresponding pattern. After that, a power transistor and a QFN are mounted on the solder composition, and reflow (in the air) is performed under the conditions of preheating 150 to 180 ° C. for 80 seconds and a peak temperature of 240 ° C. for a melting time of 40 seconds to prepare a test substrate. did. The solder joint portion of the obtained test substrate was observed using an X-ray inspection apparatus (“NLX-5000”, manufactured by NAGOYA ELECTRIC WORKS). Then, the void ratio [(void area / land area) × 100] in the power transistor and QFN after the reflow was measured.
Then, the void was evaluated according to the following criteria.
◯: The void area ratio is 15% or less.
X: The void area ratio is more than 15% and 20% or less.
XX: The void area ratio is more than 20%.
(2) Printability Diameters are 0.2 mmφ, 0.22 mmφ, 0.24 mmφ, 0.26 mmφ, 0.28 mmφ, 0.3 mmφ, 0.32 mmφ, 0.34 mmφ, 0.36 mmφ, 0.38 mmφ and 0.4 mmφ A test plate was obtained by printing the solder composition on a substrate under the conditions of a printing speed of 50 mm / sec and a printing pressure of 20 N using a plate having 100 holes each of the above and having a thickness of 0.13 mm. .. Then, the obtained test plate was analyzed by an image inspection machine, the volume ratio (volume fraction) of the solder composition with holes was measured at 100 points, and the printability was evaluated according to the following criteria.
◯: Of the 100 locations having a diameter of 0.24 mmφ, all the missing volume fractions are 70% or more.
Δ: Among 100 locations having a diameter of 0.24 mmφ, there are locations where the volume fraction is less than 70%, but there are locations where the volume fraction is 70% or more.
X: Of the 100 locations having a diameter of 0.24 mmφ, all the missing volume fractions are less than 70%. On the other hand, out of 100 places having a diameter of 0.26 mmφ, all the missing volume fractions are 70% or more.
(3) Solder meltability The diameters are 0.2 mmφ, 0.22 mmφ, 0.24 mmφ, 0.26 mmφ, 0.28 mmφ, 0.3 mmφ, 0.32 mmφ, 0.34 mmφ, 0.36 mmφ, 0.38 mmφ and 0. A test plate is obtained by printing the solder composition on a substrate under the conditions of a printing speed of 50 mm / sec and a printing pressure of 20 N using a plate having 100 holes of 4 mmφ and a thickness of 0.13 mm. It was. Then, the obtained test plate was reflowed (in the air) under the conditions of preheating 150 to 180 ° C. for 80 seconds, a peak temperature of 240 ° C. and a melting time of 40 seconds. Then, the test plate after the reflow was visually observed, and the solder meltability was evaluated according to the following criteria.
⊚: Solder melting was confirmed in the printed portion having a diameter of 0.22 mmφ.
◯: There was no solder melting in the printed portion having a diameter of 0.22 mmφ, but solder melting was confirmed in the printed portion having a diameter of 0.24 mmφ.
X: There was no solder melting in the printed portion having a diameter of 0.26 mmφ or less, but solder melting was confirmed in the printed portion having a diameter of 0.28 mmφ.
(4) Adhesiveness The adhesiveness was evaluated according to the following criteria by the method described in Annex 9 of JIS Z3284 (1994).
◯: The adhesive strength after printing is 1N or more, and the adhesive strength after being left for 12 hours under the condition of 25 ° C. and 50% is 1N or more.
X: The adhesive strength after printing is 1N or more, but the adhesive strength after being left for 12 hours under the condition of 25 ° C. and 50% is less than 1N.
(5) Viscosity change during continuous printing First, the initial viscosity is measured using the solder composition as a sample. Then, the sample is placed on a sealed metal mask, and a continuous printing test is performed in which the squeegee is continuously moved for 12 hours. Then, the viscosity of the sample after the continuous printing test is measured. Next, the viscosity change rate [{(η2-η1) / η1} × 100] with respect to the initial viscosity value (η1) with the viscosity value (η2) of the sample after the continuous printing test is obtained. The viscosity is measured by a spiral type viscosity measurement (measurement temperature: 25 ° C., rotation speed: 10 rpm).
Then, based on the result of the viscosity change rate, the viscosity change during continuous printing was evaluated according to the following criteria.
◯: The viscosity change rate is 10% or less.
X: The viscosity change rate is more than 20%.
(6) Copper plate corrosion A test was conducted in accordance with the method described in JIS Z 3197 (1999). Specifically, the test was carried out by the method described in JIS Z 3197 (1999) except that the test time was changed to 120 hours. Then, the copper plate corrosion was evaluated according to the following criteria.
◯: No corrosion or discoloration.
Δ: There is slight corrosion or slight discoloration.

As is clear from the results shown in Table 1, the solder compositions of the present invention (Examples 1 to 5) have good results of voids, printability, solder meltability, adhesiveness, and viscosity changes during continuous printing. It was confirmed that. Therefore, it was confirmed that the solder composition of the present invention has excellent solder meltability even when the reflow process is performed in an air atmosphere, can sufficiently suppress voids, and has sufficient printability.

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

Claims (4)

A flux composition containing (A) a rosin-based resin, (B) an activator and (C) a solvent, and (D) a solder powder having a melting point of 200 ° C. or higher and 250 ° C. or lower are contained.
The component (A) contains a hydrogenated additive of (A1) unsaturated organic acid-modified rosin.
The component (C) is a hexanediol-based solvent having a melting point of (C1) of 40 ° C. or higher and a boiling point of 220 ° C. or lower, and (C2) having a viscosity of 10 mPa · s or less at 20 ° C. and a boiling point of 10 mPa · s or less. Contains a solvent that is 270 ° C or higher,
Amount of the component (A), relative to the flux composition 100 wt% state, and are more than 30 wt%,
The mass ratio of the component (A1) to the component (A) [{(A1) / (A)} × 100] is 50% by mass or more.
The blending amount of the component (C) is 20% by mass or more and 65% by mass or less with respect to 100% by mass of the flux composition.
The mass ratio ((C2) / (C1)) of the component (C2) to the component (C1) is 1 or more and 10 or less.
The total blending amount of the component (C1) and the component (C2) is 50% by mass or more with respect to 100% by mass of the component (C).
A solder composition characterized by that. In the solder composition according to claim 1,
A solder composition, wherein the component (C1) is at least one selected from the group consisting of 2,5-dimethylhexane-2,5-diol and 1,6-hexanediol. In the solder composition according to claim 1 or 2.
A solder composition, wherein the component (C2) is tetraethylene glycol dimethyl ether. Using a solder composition according to any one of claims 1 to 3, a method of manufacturing an electronic substrate, and forming a soldering portion.