JP6653686B2 - Solder composition and electronic substrate - Google Patents

Description

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

The solder composition is a mixture obtained by kneading a flux composition (a rosin-based resin, an activator, a solvent, and the like) with a solder powder to form a paste (for example, Patent Document 1). In this solder composition, in addition to solderability such as solder melting property and a property that solder easily spreads (solder wet spreading), suppression of voids and printability are required.
On the other hand, with the diversification of functions of electronic devices, large-sized electronic components have been mounted on electronic substrates. Further, among large electronic components, there are electronic components (for example, power transistors) having a large electrode terminal area. In such an electronic component, since the printed area of the solder composition is large, voids having a large diameter tend to be easily generated.

Patent No. 5756067

  In the solder composition, use of a solvent having a high boiling point and a high viscosity such as isobornylcyclohexanol has been studied in order to reduce voids having a large diameter. However, even with such a solvent having a high boiling point and a high viscosity, the effect of reducing large-diameter voids may be insufficient for electronic components having a large electrode terminal area such as a power transistor. Do you get it. Furthermore, it has been found that the reflow process may be performed on the electronic substrate a plurality of times, but the voids may be further enlarged by repeating the reflow process.

  Therefore, the present invention provides a solder composition that can sufficiently suppress large-diameter voids and can sufficiently suppress squeegee adhesion even when the printed area of the solder composition is large, and to provide an electronic substrate using the same. With the goal.

In order to solve the above problems, the present invention provides the following solder composition and electronic substrate.
The solder composition of the present invention comprises (A) a flux composition containing a rosin-based resin, (B) an activator, (C) a solvent and (D) a thixotropic agent, and (E) a solder powder. The component (A) contains (A1) a rosin-based resin having an acid value of 200 mgKOH / g or more, and (A2) a rosin-based resin having an acid value of less than 200 mgKOH / g. (B1) a solvent containing an organic acid, wherein the component (C) is at least one selected from the group consisting of (C1) isobornylcyclohexanol and diisopropyl sebacate, and (C2) a solvent having a boiling point of 245 ° C. or lower. and, (C3) containing tetraethylene glycol dimethyl ether, wherein (a) the amount of component is, relative to the flux composition 100 wt%, at least 20 wt% 60 wt% or less The amount of the component (B) is 0.5% by mass or more and 5% by mass or less based on 100% by mass of the flux composition, and the amount of the component (C) is 20% by mass or more and 60% by mass or less with respect to 100% by mass, and the compounding amount of the component (D) is 3% by mass or more and 20% by mass or less with respect to 100% by mass of the flux composition. The compounding amount of the component (A1) is 18% by mass or less with respect to 100% by mass of the flux composition, and the compounding amount of the component (B1) is 2% with respect to 100% by mass of the flux composition. or less by mass%, the (C3) amount of component, relative to the flux composition 100% by weight, 10% by mass or more, the amount of the flux composition, the solder composition 100 wt% To 10. It is characterized in that the mass% or more and 11.5 mass% or less.

In the solder composition of the present invention, the component (E) is preferably a solder powder having a melting point of 210 ° C. or more and 250 ° C. or less.
An electronic substrate according to the present invention includes a soldered portion using the solder composition.

According to the solder composition of the present invention, even when the printed area of the solder composition is large, it is not always clear why large voids can be sufficiently suppressed and squeegee adhesion can be sufficiently suppressed. Guess as follows.
That is, in the solder composition of the present invention, one of (C1) isobornylcyclohexanol and diisopropyl sebacate is used as the solvent (C). Since the component (C1) has a high boiling point, it hardly volatilizes before the solder is melted. Therefore, generation of voids due to evaporation of the solvent can be suppressed. Further, since the solder composition containing the component (C1) has a certain degree of fluidity even when the solder is melted, the gas in the solder composition can be released to the outside while gradually collecting. However, when the printed area of the solder composition is large, the flowability of the solder composition is insufficient, so that the gas cannot be completely released to the outside when the solder is melted and remains as a void having a large diameter. By such a mechanism, the present inventors presume that when the printed area of the solder composition is large, a void having a large diameter is generated in the solder composition containing the component (C1).
In the solder composition of the present invention, as the solvent (C), in addition to the component (C1), a solvent (C2) having a boiling point of 245 ° C. or lower is used in combination. Since the component (C2) has a relatively low boiling point, the component volatilizes even before the solder melts and becomes a gas. This gas has an effect of pushing out the gas in the solder composition to the outside. As a result, when the printed area of the solder composition is large, the void having a large diameter can be sufficiently suppressed by the combination of the component (C1) and the component (C2).
In addition, in the solder composition of the present invention, as a solvent (C), in addition to the component (C1) and the component (C2), (C3) tetraethylene glycol dimethyl ether (having a viscosity of 3.8 mPa · s at 20 ° C.) And a solvent having a boiling point of 275 ° C.). The component (C3) has substantially the same effect as the component (C2). On the other hand, unlike the component (C2), the component (C3) tends to remain in the solder composition even after the first reflow. Also, at the time of the second and subsequent reflows, an effect of pushing out the gas in the solder composition to the outside can be exerted. Therefore, even when reflow processing is performed a plurality of times, it is possible to suppress further enlargement of voids.
Further, in the solder composition of the present invention, (A1) a rosin resin having an acid value of 200 mgKOH / g or more, and (A2) a rosin resin having an acid value of less than 200 mgKOH / g, as the rosin resin. A resin is used in combination, and the amount of the component (A1) is reduced. The present inventors have found that in a solder composition having a solvent composition containing the components (C1) to (C3), voids having a larger diameter are generated as the amount of the component (A1) increases. Although the mechanism is not necessarily clear, the present inventors have concluded that the component (A1) has a high acid value, so that the carboxylic acid component is easily decomposed, the gas of the carboxylic acid component is generated, and the voids are easily enlarged. Infer. In the solder composition of the present invention, the compounding amount of the component (A1) is suppressed, so that a further increase in voids can be suppressed.
On the other hand, the present inventors presume that the squeegee adhesion of the solder composition is due to the following mechanism. When a solder composition having too low spinnability is used, the cut of the solder composition between the squeegee and the mask becomes too good. Then, the solder composition that should be drawn to the mask side remains on the squeegee side. Therefore, the present inventors speculate that in the solder composition of the present invention, by increasing the ratio of the flux composition to the solder powder, the spinnability can be increased and the squeegee adhesion can be suppressed.
The present inventors presume that the effects of the present invention are achieved as described above.

  ADVANTAGE OF THE INVENTION According to this invention, even when the printing area of a solder composition is large, the void of a large diameter can be suppressed sufficiently, and also the solder composition which can fully suppress squeegee adhesion, and the electronic board using the same can be provided.

  The solder composition of the present embodiment contains a flux composition described below and a solder powder (E) described below.

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

[(A) component]
The rosin-based resin (A) used in the present embodiment includes rosins and rosin-modified resins. Rosins include gum rosin, wood rosin and tall oil rosin. Examples of the rosin-modified resin include disproportionated rosin, polymerized rosin, hydrogenated rosin (fully hydrogenated rosin, partially hydrogenated rosin, and unsaturated unsaturated monobasic such as unsaturated organic acid ((meth) acrylic acid). Unsaturated organic acids such as acids, fumaric acid, maleic acids, etc., aliphatic unsaturated dibasic acids such as α, β-unsaturated carboxylic acids, cinnamic acid, etc.) And hydrogenated acid-modified rosin (also referred to as “hydrogenated acid-modified rosin”) and derivatives thereof. These rosin-based resins may be used alone or in a combination of two or more.

In the present embodiment, the component (A) needs to contain (A1) a rosin resin having an acid value of 200 mgKOH / g or more, and (A2) a rosin resin having an acid value of less than 200 mgKOH / g. It is. As such a component (A1), a high acid value rosin resin having an acid value of 200 mgKOH / g or more among the components (A) is exemplified. Further, from the viewpoint of the activity, the acid value of the component (A1) is preferably 220 mgKOH / g or more. The softening point can be measured by the ring and ball method.
As the component (A2), a low-acid-value rosin-based resin having an acid value of less than 200 mgKOH / g among the components (A) is exemplified. From the viewpoint of suppressing the adhesion of voids and squeegees, the acid value of the component (A2) is preferably 190 mgKOH / g or less, more preferably 180 mgKOH / g or less.
As a means for adjusting the acid value of the component (A), a method of modifying the rosin may be changed (for example, an acid value tends to increase by modification with acrylic acid or maleic acid). Can be

  In the present embodiment, the blending amount of the component (A1) needs to be 18% by mass or less based on 100% by mass of the flux composition. If the amount exceeds 18% by mass, the generation of huge voids cannot be suppressed. From the viewpoint of further suppressing voids, the amount of the component (A1) is preferably from 5% by mass to 17% by mass, and more preferably from 10% by mass to 17% by mass.

  The amount of the component (A) is preferably from 20% by mass to 60% by mass, more preferably from 25% by mass to 50% by mass, based on 100% by mass of the flux composition. When the compounding amount of the component (A) is at least the lower limit, the oxidation of the copper foil surface of the soldering land can be prevented and the molten solder can be easily wetted on the surface. Can be suppressed. In addition, when the amount of the component (A) is equal to or less than the upper limit, the amount of flux residue can be sufficiently suppressed.

[Component (B)]
The (B) activator used in the present embodiment needs to contain (B1) an organic acid. Further, it is necessary that the blending amount of the component (B1) is 2% by mass or less based on 100% by mass of the flux composition. When the amount of the component (B1) exceeds 2% by mass, and when the printed area of the solder composition is large, voids having a large diameter cannot be sufficiently suppressed. The blending amount of the component (B1) is more preferably 1.5% by mass or less, and particularly preferably 1% by mass or less, based on 100% by mass of the flux composition.

Examples of the organic acid include a monocarboxylic acid, a dicarboxylic acid, and other organic acids.
Monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, myristic acid, pentadecyl acid, palmitic acid, margaric acid, stearic acid, and tuberculostearic acid. Arachidic acid, behenic acid, lignoceric 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, trimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anisic acid, citric acid, picolinic acid and the like.

  In the present embodiment, a known activator other than the component (B1) (the component (B2)) may be used as the component (B). Examples of such a component (B2) include a non-dissociative activator composed of a non-dissociable halogenated compound, an amine activator, and the like. These activators may be used alone or in a combination of two or more.

  Examples of the non-dissociated activator include non-salt organic compounds in which a halogen atom is bonded by a covalent bond. The halogenated compound may be a compound formed by a covalent bond of each single element of chlorine, bromine and fluorine, such as chlorinated, brominated and fluoride, but may be any two or all of chlorine, bromine and fluorine. 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 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 brominated alcohols such as tribromoneopentyl alcohol, chlorinated alcohols such as 1,3-dichloro-2-propanol and 1,4-dichloro-2-butanol, fluorinated alcohols such as 3-fluorocatechol, and Others include similar compounds. Examples of the halogenated carboxyl compound include 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, and iodocarboxyl compounds such as 5-iodoanthranilic acid, 2-chlorobenzoic acid, and 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 activator include amines (eg, polyamines such as ethylenediamine), amine salts (eg, amines such as trimethylolamine, cyclohexylamine, and diethylamine, and organic acid salts and inorganic acid salts such as aminoalcohols (eg, hydrochloric acid, sulfuric acid, Hydrobromic acid)), amino acids (such as glycine, alanine, aspartic acid, glutamic acid, and valine), and amide compounds. Specifically, diphenylguanidine hydrobromide, cyclohexylamine hydrobromide, diethylamine salt (such as hydrochloride, succinate, adipate, and sebacate), triethanolamine, monoethanolamine, And hydrobromides of these amines.

  The blending amount of the component (B) is preferably from 0.5% by mass to 5% by mass, and more preferably from 0.7% by mass to 4% by mass with respect to 100% by mass of the flux composition. It is more preferable that the content be 1% by mass or more and 3% by mass or less. When the amount is equal to or more than the lower limit, the solder balls can be more reliably suppressed. In addition, when the compounding amount is equal to or less than the upper limit, insulation reliability of the flux composition can be secured.

[(C) component]
The (C) solvent used in the present embodiment is at least one selected from the group consisting of (C1) isobornylcyclohexanol and diisopropyl sebacate, (C2) a solvent having a boiling point of 245 ° C. or lower, and (C3) ) It is necessary to contain tetraethylene glycol dimethyl ether. By using the components (C1), (C2) and (C3) in combination, it is possible to sufficiently suppress large-diameter voids even when the printed area of the solder composition is large.

  In addition, from the viewpoint of further suppressing voids, the boiling point of the component (C2) is more preferably 220 to 245 ° C, and particularly preferably 230 to 243 ° C. In addition, in this specification, a boiling point means the boiling point in 1013 hPa.

  As the component (C2), phenyl glycol (boiling point: 245 ° C.), 2-ethyl-1,3-hexanediol (boiling point: 244 ° C.), dipropylene glycol monophenyl ether (boiling point: 243 ° C.), tripropylene glycol monomethyl Ether (boiling point: 242 ° C), dipropylene glycol monobutyl ether (boiling point: 231 ° C), ethylene glycol mono-2-ethylhexyl ether (boiling point: 229 ° C), diethylene glycol monobutyl ether (boiling point: 231 ° C) and diethylene glycol monoethyl ether acetate (boiling point: 231 ° C) (Boiling point: 220 ° C.). These may be used alone or as a mixture of two or more.

  (C3) Tetraethylene glycol dimethyl ether is a solvent having a boiling point of 275 ° C. With the component (C3), the enlargement of voids due to a plurality of reflows can be suppressed.

  In the present embodiment, the blending amount of the component (C3) needs to be 10% by mass or more based on 100% by mass of the flux composition. If the compounding amount is less than 10% by mass, it is not possible to suppress the enlargement of voids caused by a plurality of reflows. From the viewpoint of further suppressing voids, the amount of the component (C3) is preferably from 12% by mass to 35% by mass, and more preferably from 15% by mass to 25% by mass.

The component (C) may contain a solvent other than the components (C1), (C2) and (C3) (component (C4)) as long as the object of the present invention can be achieved. When the component (C4) is used, the total amount of the component (C1), the component (C2) and the component (C3) is preferably at least 80% by mass based on 100% by mass of the component (C). It is more preferably at least 90% by mass, particularly preferably at least 95% by mass.
Examples of the component (C4) include diethylene glycol monohexyl ether (boiling point: 259 ° C.). These may be used alone or as a mixture of two or more. In addition, the viscosity described in parentheses is the viscosity at 20 ° C.

  The compounding amount of the component (C) is preferably 20% by mass or more and 60% by mass or less, more preferably 25% by mass or more and 55% by mass or less, and more preferably 30% by mass or less with respect to 100% by mass of the flux composition. % Is particularly preferable. If the amount of the solvent is within the above range, the viscosity of the obtained solder composition can be appropriately adjusted to an appropriate range.

[(D) component]
Examples of the (D) thixotropic agent used in the present embodiment include hardened castor oil, polyamides, amides, kaolin, colloidal silica, organic bentonite, and glass frit. Among these, from the viewpoint of suppressing voids, polyamides and amides are more preferred. Examples of commercially available polyamides or amides include “Tallen” manufactured by Kyoeisha Chemical Co., Ltd. One of these thixotropic agents may be used alone, or two or more thereof may be used in combination.

  The compounding amount of the component (D) is preferably 3% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 15% by mass or less based on 100% by mass of the flux composition. When the amount is at least the lower limit, sufficient thixotropy can be obtained, and sag can be sufficiently suppressed. If the compounding amount is less than the above upper limit, the thixotropy is too high and no printing failure occurs.

[Other components]
In the flux composition used in the present invention, in addition to the component (A), the component (B), the component (C) and the component (D), if necessary, other additives and further other resins may be used. Can be added. Other additives include defoamers, antioxidants, modifiers, matting agents, foaming agents, and the like. Other resins include acrylic resins.

[Solder composition]
Next, the solder composition of the present embodiment will be described. The solder composition of the present embodiment contains the flux composition of the present embodiment and (E) a solder powder described below.
In the present embodiment, the amount of the flux composition needs to be 10.4% by mass or more and 11.5% by mass or less based on 100% by mass of the solder composition. If the compounding amount of the flux composition is less than 10.4% by mass (the compounding amount of the solder powder exceeds 89.6% by mass), squeegee adhesion cannot be suppressed. On the other hand, if the amount of the flux composition exceeds 11.5% by mass, the chip side balls cannot be suppressed. The amount of the flux composition is more preferably 10.4% by mass or more and 11.2% by mass or less based on 100% by mass of the solder composition.

[(E) component]
The (E) solder powder used in the present embodiment is preferably composed of only a lead-free solder powder, but may be a leaded solder powder. As a solder alloy in the solder powder, an alloy containing tin (Sn) as a main component is preferable. The second element of the alloy includes silver (Ag), copper (Cu), zinc (Zn), bismuth (Bi), indium (In), and antimony (Sb). Further, other elements (third and subsequent elements) 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, the presence of lead as an unavoidable impurity in the lead-free solder powder is acceptable, but in this case, the amount of lead is preferably 300 ppm by mass or less.

  As the solder alloy in the lead-free solder powder, specifically, Sn-Ag, Sn-Ag-Cu, Sn-Cu, Sn-Ag-Bi, Sn-Bi, Sn-Ag-Cu-Bi, Sn-Sb , Sn-Zn-Bi, Sn-Zn, Sn-Zn-Al, Sn-Ag-Bi-In, Sn-Ag-Cu-Bi-In-Sb, In-Ag and the like. 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 from 200C to 250C. In addition, among Sn-Ag-Cu solders, the melting point of the solder having a low silver content is 210 ° C. or more and 250 ° C. or less (220 ° C. or more and 240 ° C. or less).

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

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

[Electronic substrate]
Next, the electronic substrate of the present embodiment will be described. The electronic substrate according to the present embodiment includes a soldered portion using the above-described solder composition. The electronic substrate of the present embodiment can be manufactured by mounting an electronic component on an electronic substrate (such as a printed wiring board) using the solder composition.
The solder composition of the present embodiment can sufficiently suppress large-diameter voids 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. Note that the printing area corresponds to the area of the electrode terminal of the electronic component.
Examples of the coating device used here include a screen printing machine, a metal mask printing machine, a dispenser, and a jet dispenser.
Further, the electronic component is placed on the solder composition applied by the coating device, heated by a reflow oven under predetermined conditions, and the electronic component is mounted on a printed wiring board by a reflow process. Can be implemented.

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 step, a sufficient solder joint 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 condition may be appropriately set according to the melting point of the solder. For example, when using a Sn-Ag-Cu-based solder alloy, the preheat temperature is set to 150 to 200 ° C, the preheat time is set to 60 to 120 seconds, and the peak temperature is set to 230 to 270 ° C. Good.

[Modification]
Further, the solder composition and the electronic substrate of the present invention are not limited to the above-described embodiment, and modifications and improvements as long as 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 bonded to each other 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 adjusted to the absorption band of the metal. As the laser light source, for example, a solid laser (ruby, glass, YAG, etc.), a semiconductor laser (GaAs, InGaAsP, etc.), a liquid laser (dye, etc.), and a gas laser (He—Ne, Ar, CO ₂ , and Excimer, 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 the examples and comparative examples are shown below.
((A1) component)
Rosin-based resin A: hydrogenated acid-modified rosin (acid value: 240 mg KOH / g), trade name “Pine Crystal KE-604”, manufactured by Arakawa Chemical Industry Co., Ltd. (component (A2))
Rosin-based resin B: completely hydrogenated rosin (acid value: 165 mg KOH / g), trade name “Foral AX”, rosin-based resin manufactured by Eastman Chemical Co .: C-polymerized rosin (acid value: 145 mg KOH / g), trade name “pine crystal” KR-140 ", manufactured by Arakawa Chemical Industries, Ltd. ((B1) component)
Organic acid A: succinic acid Organic acid B: malonic acid ((B2) component)
Activator: dibromobutenediol (component (C1))
Solvent A: isobornylcyclohexanol Solvent B: diisopropyl sebacate (component (C2))
Solvent C: tripropylene glycol monomethyl ether (boiling point: 242 ° C., viscosity: 1 mPa · s)
((C3) component)
Solvent D: tetraethylene glycol dimethyl ether (boiling point: 275 ° C, viscosity: 3.8 mPa · s)
((D) component)
Thixotropic agent A: trade name “Tallen VA79”, Kyoeisha Chemical Co., Ltd. thixotropic agent B: trade name “Diamid Y”, manufactured by Nippon Kasei Co. (component (E))
Solder powder: alloy composition: Sn-3.0Ag-0.5Cu, particle size distribution: 20-38 μm, solder melting point: 217-220 ° C.

[Example 1]
15% by mass of rosin-based resin A, 23.7% by mass of rosin-based resin B, 0.3% by mass of organic acid A, 0.3% by mass of organic acid B, 1% by mass of activator, 13.6% by mass of solvent A, 10.8% by mass of solvent C %, Solvent D 24% by mass, thixo agent A 4.8% by mass and thixo agent B 6.5% by mass were charged into a container and mixed using a planetary mixer to obtain a flux composition.
Thereafter, 10.2% by mass of the obtained flux composition and 89.8% by mass of the solder powder (100% by mass in total) were charged into a container, and mixed with a planetary mixer to prepare a solder composition.

[Examples 2 to 4 ]
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 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.

<Evaluation of solder composition>
Evaluation of the solder composition (maximum void diameter in power transistor, spinnability, ball on chip side) was performed by the following method. Table 1 shows the obtained results. In addition, when the evaluation result of the maximum void diameter in the power transistor was bad, evaluation of the spinnability and the ball beside the chip was omitted in some cases.
(1) Maximum void diameter in a power transistor On a substrate having electrodes on which a power transistor (size: 5.5 mm × 6.5 mm, thickness: 2.3 mm, land: tin plating, land area: 30 mm ² ) can be mounted. Then, a solder composition was printed using a metal mask having a corresponding pattern. Thereafter, a power transistor is mounted on the solder composition, and reflow is performed under the conditions of a preheat of 150 to 180 ° C. for 80 seconds, a peak temperature of 240 ° C., and a melting time of 40 seconds (in nitrogen, oxygen concentration of 1000 ppm or less), and a test. A substrate was prepared. The solder joints on the obtained test board were observed using an X-ray inspection apparatus (“NLX-5000”, manufactured by NAGOYA ELECTRIC WORKS). The void in the power transistor after the first reflow was observed, and the diameter of the largest void among the voids was measured as the maximum void diameter (unit: mm).
Furthermore, the test board after the first reflow was subjected to a second reflow under the same conditions as the first reflow, and the solder joint was observed. Then, the maximum void diameter (unit: mm) in the power transistor after the second reflow was measured.
(2) Spinnability The obtained solder composition (temperature: 25 ° C.) in a container was charged, and the solder composition was stirred for 30 seconds at a rotation speed of 10 rpm. Thereafter, a measuring rod having a thread portion was immersed in the solder composition such that the entire thread portion was immersed. Thereafter, the measuring rod was pulled up at a speed of 500 mm / min, and at this time, the length (mm) when the thread formed between the thread portion and the solder composition was cut was measured.
The threading portion includes a conical conical portion at the tip, a columnar cylindrical portion, and a connecting portion that connects the columnar portion and the measuring rod. The diameter of the conical part and the cylindrical part is 10 mm, the height of the conical part is 5 mm, the length of the cylindrical part is 9 mm, the length of the connecting part is 3 mm, and the diameter of the measuring rod is 3 mm It is. In addition, "EZ-L" manufactured by SIMAZU was used as a device for lifting the measuring rod.
(3) Chip side ball A solder composition is printed on a substrate for evaluation on which a chip component (3216 chip) can be mounted using a metal mask having a thickness of 120 μm, 60 chip components are mounted, and a reflow furnace (Tamura Seisakusho) The test composition is obtained by dissolving the solder composition in the above method and soldering. The reflow conditions here are a preheat temperature of 150 to 180 ° C. (60 seconds), a time of 220 ° C. or higher for 50 seconds, and a peak temperature of 245 ° C. The obtained test plate was observed with a magnifying glass, and the number (pieces / chip) of solder balls generated beside the chip component was measured.
Then, based on the result of the number of solder balls (pieces / chip), the chip side balls were evaluated according to the following criteria.
：: The number of solder balls per chip is less than two.
Δ: The number of solder balls per chip is 2 or more and less than 3.
X: The number of solder balls per chip is three or more.

As is clear from the results shown in Table 1, it contains the component (A1), the component (A2), the component (C1), the component (C2) and the component (C3), and the component (A1) and the component (B1). The solder composition of the present invention (Examples 1 to 4 ), in which the amount of (C3) is not less than the predetermined value, the amount of the component (C3) is not less than the predetermined value, and the amount of the flux composition is in an appropriate range. When used, it was confirmed that the maximum void diameter in the power transistor was small, the measured value of the spinnability was high, and the ball beside the tip was suppressed. It has been found that the higher the measured spinnability, the more the squeegee adhesion can be sufficiently suppressed. Therefore, it was confirmed that the solder composition of the present invention can sufficiently suppress large-diameter voids and sufficiently suppress squeegee adhesion even when the printed area of the solder composition is large.

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

Claims (3)

A flux composition containing (A) a rosin-based resin, (B) an activator, (C) a solvent and (D) a thixotropic agent, and (E) a solder powder;
The component (A) contains (A1) a rosin-based resin having an acid value of 200 mgKOH / g or more, and (A2) a rosin-based resin having an acid value of less than 200 mgKOH / g,
The component (B) contains (B1) an organic acid,
The component (C) is (C1) at least one selected from the group consisting of isobornylcyclohexanol and diisopropyl sebacate, (C2) a solvent having a boiling point of 245 ° C. or lower, and (C3) tetraethylene glycol Contains dimethyl ether,
The amount of the component (A) is 20% by mass or more and 60% by mass or less based on 100% by mass of the flux composition;
The compounding amount of the component (B) is 0.5% by mass or more and 5% by mass or less based on 100% by mass of the flux composition;
The compounding amount of the component (C) is 20% by mass or more and 60% by mass or less based on 100% by mass of the flux composition;
The compounding amount of the component (D) is 3% by mass or more and 20% by mass or less based on 100% by mass of the flux composition;
The compounding amount of the component (A1) is 18% by mass or less based on 100% by mass of the flux composition;
The compounding amount of the component (B1) is 2% by mass or less based on 100% by mass of the flux composition;
The amount of the component (C3) is 10% by mass or more based on 100% by mass of the flux composition;
The solder composition, wherein the amount of the flux composition is 10.4% by mass or more and 11.5% by mass or less based on 100% by mass of the solder composition. The solder composition according to claim 1,
The solder composition, wherein the component (E) is a solder powder having a melting point of 210 ° C. or more and 250 ° C. or less.   An electronic substrate, comprising: a soldered part using the solder composition according to claim 1.