JP7220694B2 - FLUX COMPOSITION, SOLDER COMPOSITION, AND METHOD FOR MANUFACTURING ELECTRONIC SUBSTRATE - Google Patents

Description

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

The solder composition is a paste-like mixture obtained by kneading solder powder with a flux composition (a composition containing a rosin-based resin, an activator, a solvent, and the like). This solder composition is required to have good solderability such as solder meltability and the property that solder easily spreads by wetting (solder wetting and spreading). In order to meet these demands, activators and the like in flux compositions have been studied (for example, Patent Document 1).
On the other hand, mobile terminals such as smartphones are becoming smaller and more functional. Electronic parts used for these are also miniaturized. It is necessary to join the lands with a small area of such electronic parts with a small amount of solder composition. Solder compositions are also used on large substrates. When using a solder composition for such a large substrate, it is necessary to lengthen the preheating time in the reflow process. Furthermore, in the case of a large-sized substrate, the heat capacity is large and it takes time to reach the preheating temperature. In such cases, activators such as low-molecular-weight organic acids are susceptible to deactivation, resulting in poor meltability in small areas. On the other hand, when the amount of activator is increased, problems such as copper corrosion tend to occur. Thus, there is a demand for a solder composition that can be used for large-sized substrates while coping with miniaturization of electronic components.

JP 2013-169557 A

An object of the present invention is to provide a flux composition, a solder composition, and a method for manufacturing an electronic substrate, which are excellent in meltability in a small area and capable of suppressing copper corrosion.

According to one aspect of the present invention, there is provided a flux composition containing (A) a rosin-based resin, (B) an activator, (C) a solvent, and (D) an antioxidant, wherein the component (D) is and (D1) a flux composition containing a compound represented by the following structural formula (D1), wherein the component (D) is contained in an amount of 4% by mass or more with respect to 100% by mass of the flux composition provided.

In the flux composition according to one aspect of the present invention, the component (D) preferably further contains (D2) an antioxidant having a hindered phenol structure (excluding component (D1)).
In the flux composition according to one aspect of the present invention, the component (B) contains (B1) an organic acid having 10 or more carbon atoms, and the content of (B1) is 100% by mass of the flux composition. is preferably 8% by mass or more and 20% by mass or less.
In the flux composition according to one aspect of the present invention, the amount of (A) is preferably 30% by mass or more and 70% by mass or less with respect to 100% by mass of the flux composition.

According to one aspect of the present invention, there is provided a solder composition containing the flux composition according to one aspect of the present invention and (E) solder powder.
In the solder composition according to one aspect of the present invention, the solder alloy in the component (E) is tin, copper, zinc, silver, antimony, lead, indium, bismuth, nickel, gold, cobalt and germanium. It is preferable to contain at least one selected.

According to one aspect of the present invention, there is provided a method for manufacturing an electronic substrate by soldering using the solder composition according to one aspect of the present invention, wherein the electronic component is placed on the solder composition, and reflow is performed. Provided is a method for manufacturing an electronic substrate, comprising a reflow step of heating in a furnace, wherein the time to reach a melting temperature in the reflow step is 330 seconds or longer.

ADVANTAGE OF THE INVENTION According to this invention, the flux composition which is excellent in the meltability in a micro area, and can suppress copper corrosion, a solder composition, and the manufacturing method of an electronic board can be provided.

[Flux composition]
First, the flux composition used in this 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 includes (A) a rosin resin, (B) an activator, (C) a solvent, and (D) an antioxidant, which will be described below. contains

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

The amount of component (A) is preferably 30% by mass or more and 70% by mass or less, more preferably 34% by mass or more and 60% by mass or less, and 35% by mass, based on 100% by mass of the flux composition. % or more and 50 mass % or less is particularly preferable. If the blending amount of component (A) is at least the above lower limit, it is possible to prevent oxidation of the copper foil surface of the soldering land and make it easier for molten solder to wet the surface, so-called solderability can be improved, and solder balls can be sufficiently formed. can be suppressed to Moreover, if the compounding quantity of (A) component is below the said upper limit, the flux residue amount can fully be suppressed.

[(B) component]
The (B) activator used in the present embodiment preferably contains (B1) an organic acid having 10 or more carbon atoms (more preferably 11 or more carbon atoms). This component (B1) is less likely to be deactivated even when the preheating time is long, and can improve the meltability in a minute area. In addition, this component (B1) tends to be less likely to cause copper corrosion.

Component (B1) includes dodecanedioic acid, eicosanedioic acid, dimer acid, trimer acid, 1-hydroxy-2-naphthoic acid, 3-hydroxy-2-naphthoic acid, and 1,4-dihydroxy-2-naphthoic acid. etc. These may be used individually by 1 type, and may be used in mixture of 2 or more types.

The amount of component (B1) is preferably 8% by mass or more and 20% by mass or less, more preferably 10% by mass or more and 18% by mass or less, based on 100% by mass of the flux composition. If the blending amount of component (B1) is at least the lower limit, the meltability in a small area tends to be improved.

Component (B) may contain (B2) an organic acid having less than 10 carbon atoms within the range where the effects of the present invention can be achieved. However, such a low-molecular-weight organic acid having less than 10 carbon atoms is likely to be deactivated when the preheating time is long, and is likely to cause copper corrosion. The activator preferably does not contain this (B2) component.
Component (B2) includes monocarboxylic acids, dicarboxylic acids and other organic acids having less than 10 carbon atoms.
Monocarboxylic acids having less than 10 carbon atoms include formic acid, acetic acid, propionic acid, and butyric acid.
Dicarboxylic acids having less than 10 carbon atoms include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, and azelaic acid.
Other organic acids with less than 10 carbon atoms include lactic acid, benzoic acid, salicylic acid, and citric acid.

In addition to component (B1), component (B) further contains other activators ((B3) halogen-based activator, (B4) amine-based activator, etc.) to the extent that the effects of the present invention are not impaired. may However, since the (B3) component is likely to cause copper corrosion, it is preferable that the (B) component consists only of the (B1) component. The total amount of component (B1) blended is preferably 85% by mass or more, more preferably 90% by mass or more, and more preferably 95% by mass or more with respect to 100% by mass of component (B). It is particularly preferred to have

The blending amount of component (B) is preferably 8% by mass or more and 25% by mass or less, more preferably 10% by mass or more and 20% by mass or less, based on 100% by mass of the flux composition. It is particularly preferable that the content is not less than 18% by mass and not more than 18% by mass. If the blending amount of component (B) is at least the above lower limit, the activity tends to be improved, while if it is at most the above upper limit, the insulating properties of the flux composition tend to be maintained.

[(C) component]
As the (C) solvent used in the present embodiment, a known solvent can be used as appropriate. As such a solvent, it is preferable to use a solvent having a boiling point of 170° C. or higher.
Examples of such solvents include diethylene glycol, dipropylene glycol, triethylene glycol, hexylene glycol, 1,5-pentanediol, methyl carbitol, butyl carbitol, 2-ethylhexyl diglycol, octanediol, phenyl glycol, Diethylene glycol monohexyl ether (DEH), tetraethylene glycol dimethyl ether (MTEM), dibutyl maleate, and the like. One type of these solvents may be used alone, or two or more types may be mixed and used.

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

[(D) component]
The (D) antioxidant used in this embodiment must contain (D1) a compound represented by the following structural formula (D1). This (D1) component can improve the meltability in a small area and can suppress copper corrosion due to the (B) component. This (D1) component is N,N'-bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl}hydrazine.

The amount of component (D1) is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.2% by mass or more and 5% by mass or less, based on 100% by mass of the flux composition. It is preferably 0.5% by mass or more and 2% by mass or less, particularly preferably. If the blending amount of the component (D1) is within the above range, the meltability in a small area can be improved, and copper corrosion can be suppressed.

Component (D) preferably further contains (D2) an antioxidant having a hindered phenol structure (excluding component (D1)) from the viewpoint of meltability in a small area and suppression of copper corrosion.
(D2) components include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], bis[3-(3-tert-butyl-4-hydroxy-5-methyl phenyl)propionic acid][ethylenebis(oxyethylene)] and N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl] oxamide and the like.

When using component (D2), the mass ratio of component (D2) to component (D1) ((D2)/(D1)) is 1 or more and 10 or less, from the viewpoint of the balance between solder meltability and other physical properties. is preferably 2 or more and 9 or less, and particularly preferably 4 or more and 8 or less.

Component (D) may further contain other antioxidants (hereinafter referred to as component (D3)) in addition to components (D1) and (D2) to the extent that the effects of the present invention are not impaired. However, the (D) component preferably consists of only the (D1) component, or only the (D1) component and the (D2) component. In addition, the total amount of component (D1) and component (D2) is preferably 85% by mass or more, more preferably 90% by mass or more, relative to 100% by mass of component (D). It is preferably 95% by mass or more, and particularly preferably 95% by mass or more.

Component (D3) includes sulfur compounds (didodecyl 3,3'-thiodipropionate, etc.), benzotriazole compounds (1,2,3-benzotriazole, etc.), and phosphite compounds.

Component (D) should be added in an amount of 4% by mass or more based on 100% by mass of the flux composition. If the amount of component (D) is less than 4% by mass, the meltability in a small area will be insufficient, or copper corrosion will occur. Further, from the viewpoint of balance between solder meltability and other physical properties, the amount of component (D) is preferably 4% by mass or more and 15% by mass or less, and is 4.5% by mass or more and 10% by mass or less. is more preferable, and it is particularly preferable to be 5% by mass or more and 8% by mass or less.

[Thixotropic agent]
From the viewpoint of printability, the flux composition of the present embodiment preferably further contains a thixotropic agent. The thixotropic agent used here includes hydrogenated castor oil, amides, kaolin, colloidal silica, organic bentonite, and glass frit. These may be used individually by 1 type, and may be used in mixture of 2 or more types.

The amount of the thixotropic agent is preferably 1% by mass or more and 20% by mass or less, more preferably 2% by mass or more and 12% by mass or less, based on 100% by mass of the flux composition. If the amount is less than the above lower limit, thixotropic properties cannot be obtained and sagging tends to occur.

[Other ingredients]
The flux composition used in the present embodiment contains components (A), (B), (C), (D), and a thixotropic agent, and optionally other additives and further , and other resins can be added. Other additives include defoamers, modifiers, matting agents, blowing 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. Other resins include acrylic resins and polybutadiene.

[Solder composition]
Next, the solder composition of this embodiment will be described. The solder composition of the present embodiment contains the flux composition of the present embodiment described above and (E) solder powder described below.
The amount of the flux composition is preferably 5% by mass or more and 35% by mass or less, more preferably 7% by mass or more and 15% by mass or less, and 8% by mass with respect to 100% by mass of the solder composition. More than 12% by mass or less is particularly preferable. When the amount of the flux composition is less than 5% by mass (when the amount of the solder powder is more than 95% by mass), the flux composition and the solder powder are mixed because the flux composition as a binder is insufficient. On the other hand, when the amount of the flux composition exceeds 35% by mass (when the amount of the solder powder is less than 65% by mass), when the resulting solder composition is used, It tends to be difficult to form a good solder joint.

[(E) component]
The (E) solder powder used in the present invention preferably consists of only lead-free solder powder, but lead-containing solder powder may also be used. The solder alloy in this solder powder includes tin (Sn), copper (Cu), zinc (Zn), silver (Ag), antimony (Sb), lead (Pb), indium (In), bismuth (Bi), It preferably contains at least one selected from the group consisting of nickel (Ni), gold (Au), cobalt (Co) and germanium (Ge).
As the solder alloy in this solder powder, an alloy containing tin as a main component is preferable. Also, the solder alloy more preferably contains tin, silver and copper. Furthermore, the solder alloy may contain at least one of antimony, bismuth and nickel as additive elements. According to the flux composition of the present embodiment, even when a solder alloy containing easily oxidizable additive elements such as antimony, bismuth and nickel is used, the generation of voids can be suppressed.
Here, the lead-free solder powder means powder of solder metal or alloy to which lead is not added. However, the presence of lead as an unavoidable impurity in lead-free solder powder is allowed, but in this case, the amount of lead is preferably 300 ppm by mass or less.

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

The average particle size of the component (E) is usually 1 μm or more and 40 μm or less, but from the viewpoint of compatibility with electronic substrates with a narrow pitch of soldering pads, it is more preferably 1 μm or more and 35 μm or less, and 2 μm or more and 35 μm. It is even more preferably 3 μm or more and 32 μm or less, particularly preferably 3 μm or more and 32 μm or less. The average particle size can be measured with a dynamic light scattering particle size measuring device.

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

[Method for manufacturing electronic substrate]
Next, a method for manufacturing the electronic substrate of this embodiment will be described. The method for manufacturing an electronic substrate according to the present embodiment is characterized by using the solder composition described above. According to the method for manufacturing an electronic board of the present embodiment, an electronic board can be manufactured by mounting an electronic component on an electronic board (printed wiring board, etc.) using the solder composition.
The solder composition of the present embodiment described above has excellent meltability in a small area and can suppress copper corrosion. Therefore, it is possible to cope with the miniaturization of electronic components and also with large-sized substrates.
Examples of coating devices used here include screen printers, metal mask printers, dispensers, jet dispensers, and the like.
Further, an electronic component is placed on the solder composition applied by the coating device, heated under predetermined conditions in a reflow furnace, and the electronic component is mounted on the printed wiring board by a reflow process to mount the electronic component on the electronic board. can be implemented in

In the reflow process, the electronic component is placed on the solder composition and heated under predetermined conditions in a reflow furnace. This reflow process provides good solder joints between the electronic component and the printed wiring board. As a result, the electronic component can be mounted on a printed wiring board or the like.
Reflow conditions may be appropriately set according to the melting point of solder. For example, the preheat temperature is preferably 140° C. or higher and 200° C. or lower. The preheat time is preferably 100 seconds or more and 250 seconds or less, more preferably 120 seconds or more and 200 seconds or less, from the viewpoint of coping with a large substrate. The peak temperature is preferably 230° C. or higher and 270° C. or lower, more preferably 240° C. or higher and 255° C. or lower. In addition, the holding time at a temperature of 220° C. or higher is preferably 40 seconds or more and 160 seconds or less, more preferably 100 seconds or more and 150 seconds or less, from the viewpoint of coping with large substrates.
In addition, the time to reach the preheat temperature (for example, 140 ° C.) is preferably 180 seconds or more, more preferably 200 seconds or more, and 220 seconds or more and 500 seconds or less, from the viewpoint of handling large substrates. is particularly preferred. The time to reach the melting temperature (for example, 220° C.) is preferably 330 seconds or more, more preferably 350 seconds or more, and 360 seconds or more and 700 seconds or less, from the viewpoint of compatibility with large substrates. is particularly preferred.
As in the reflow conditions described above, the longer the solder powder is exposed to in the reflow furnace, the more the solder powder is oxidized and the solder meltability tends to deteriorate. On the other hand, the solder composition of the present embodiment described above can cope with such reflow conditions.

Moreover, the solder composition and the electronic substrate of the present embodiment are not limited to the above-described embodiments, and modifications and improvements within the range that can achieve the object of the present invention are included in the present invention.
For example, in the electronic board, the printed wiring board and the electronic component are bonded by a reflow process, but the present invention is not limited to this. For example, instead of the reflow process, the printed wiring board and the electronic component may be bonded by a process of heating the solder composition using a laser beam (laser heating process). In this case, the laser light source is not particularly limited, and can be appropriately employed depending on the wavelength matched to the absorption band of the metal. Examples of laser light sources include solid lasers (ruby, glass, YAG, etc.), semiconductor lasers (GaAs, InGaAsP, etc.), liquid lasers (dyes, etc.), and gas lasers (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. Materials used in Examples and Comparative Examples are shown below.
((A) component)
Rosin-based resin: Hydrogenated acid-modified rosin, trade name “Pine Crystal KE-604”, manufactured by Arakawa Chemical Industries, Ltd. ((B1) component)
Organic acid A: 3-hydroxy-2-naphthoic acid Organic acid B: Dodecanedioic acid Organic acid C: Dimer acid, trade name "UNIDYME14", manufactured by Arizona Chemical Company Organic acid D: Trimer acid (90% by mass or more of trimer acid) , trade name “Floradyme 6500”, manufactured by Florachem ((B2) component)
Organic acid E: Succinic acid Organic acid F: Glutaric acid Organic acid G: Adipic acid Organic acid H: Suberic acid (component (C))
Solvent A: diethylene glycol monohexyl ether (DEH, hexyl diglucol)
Solvent B: tetraethylene glycol dimethyl ether, trade name "Hisolve MTEM", manufactured by Toho Chemical Industry Co., Ltd. (component (D1))
Antioxidant A: N,N'-bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl}hydrazine, trade name "Irganox MD1024", manufactured by BASF Japan ((D2) component)
Antioxidant B: bis [3-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionic acid] [ethylene bis (oxyethylene)], trade name "Irganox 245", BASF Antioxidant Agent C: pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], trade name "ANOX20"
Antioxidant D: N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxamide, trade name "Naugard XL-1", Shiraishi Calcium Co., Ltd. ((D2) component)
Antioxidant E: 1,2,3-benzotriazole, trade name "VERZONE Crysta", manufactured by Daiwa Kasei Co., Ltd. (other ingredients)
Thixotropic agent: trade name "Slipax H", manufactured by Nippon Kasei Co., Ltd. ((E) component)
Solder powder: alloy composition Sn-3.0Ag-0.5Cu, particle size distribution 15-25 μm, solder melting point 217-220°C

[Example 1]
Rosin resin 35% by mass, organic acid A 4% by mass, organic acid B 4% by mass, organic acid C 4% by mass, solvent A 32.5% by mass, solvent B 8% by mass, antioxidant A 0.5% by mass, antioxidant B4 % by mass and 8% by mass of the thixotropic agent were put into a container and mixed using a planetary mixer to obtain a flux composition.
After that, 11.8% by mass of the flux composition and 88.2% by mass of solder powder (total 100% by mass) were put into a container and mixed by a planetary mixer to prepare a solder composition.

[Examples 2 to 6]
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 (meltability of minute lands, copper corrosion, solder balls, voids) was performed by the following methods. Table 1 shows the results obtained. In addition, evaluation of viscosity stability and wettability was partly omitted for solder compositions that had problems with their properties.
(1) Meltability of Micro Land A solder composition was printed on a substrate using a metal mask with a thickness of 0.08 mm. 100 test patterns each of copper foil pads with diameters of 0.28 mm, 0.26 mm, 0.24 mm, 0.22 mm and 0.20 mm were printed. After that, the preheat temperature is set to 140 to 200°C for 160 seconds (time to reach 140°C is 235 seconds), the holding time at 220°C or higher is 120 seconds (time to reach 220°C (melting temperature) is 413 seconds), and the peak temperature is 250°C. A test substrate was produced by performing reflow under the following conditions. The test substrate was observed under a microscope to measure the minimum melt pad diameter (unit: mmφ). The smaller the diameter, the better the meltability. From the viewpoint of excellent meltability in a small area, the minimum melt pad diameter is preferably 0.20 mm.
(2) Copper corrosion A copper foil corrosion test was performed according to the method described in IPC TM650 2.6.15C to evaluate copper corrosion. Then, when the result of the copper foil corrosion test was acceptable, it was judged as "O", and in other cases, it was judged as "X".
(3) Solder ball On the substrate, using a metal mask with a thickness of 0.08 mm, print a solder composition, mount a QFP (Quad Flat Package) with a pitch of 0.8 mm, further improve the meltability of the micro lands A reflow treatment was performed under the same conditions as the evaluation, and a substrate for evaluation was produced. The slit portion of the QFP was observed with a magnifying glass, and the number of solder balls generated between the slits was counted. Then, the solder balls were evaluated according to the following criteria.
◯: The number of balls generated per pin is 10 or less.
Δ: The number of balls generated per pin is more than 10 and 30 or less.
x: The number of balls generated per pin is more than 30.
(4) On the void substrate, using a metal mask with a thickness of 0.08 mm, printed a solder composition, mounted a 0.5 mm pitch QFN (Quad Flat Non-leaded package), further, melting of the micro land A reflow treatment was performed under the same conditions as in the evaluation of the properties, and a substrate for evaluation was produced. Then, as an X-ray inspection device, "NLX-5000" manufactured by Nagoya Electric Industry Co., Ltd. is used to measure voids, and using the standard application of the device, the void area ratio [(total void area /total land area)×100]. Voids were evaluated according to the following criteria.
○: The void area ratio is 20% or less.
Δ: The void area ratio is more than 20% and 25% or less.
x: The void area ratio is more than 25%.

As is clear from the results shown in Table 1, the solder compositions of the present invention (Examples 1 to 6) are excellent in all of the meltability of micro lands, copper corrosion, solder balls, and voids. was confirmed.
Therefore, it was confirmed that the solder composition of the present invention has excellent meltability in a small area and can suppress copper corrosion.

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

Claims (4)

A flux composition containing (A) a rosin-based resin, (B) an activator, (C) a solvent, and (D) an antioxidant,
The content of component (A) is 30% by mass or more and 70% by mass or less with respect to 100% by mass of the flux composition,
The component (B) contains (B1) an organic acid having 10 or more carbon atoms,
The content of (B1) is 8% by mass or more and 20% by mass or less with respect to 100% by mass of the flux composition,
The total amount of the component (B1) blended is 85% by mass or more with respect to 100% by mass of the component (B),
The content of component (B) is 8% by mass or more and 25% by mass or less with respect to 100% by mass of the flux composition,
The content of component (C) is 10% by mass or more and 60% by mass or less with respect to 100% by mass of the flux composition,
The (D) component contains (D1) a compound represented by the following structural formula (D1) and (D2) an antioxidant having a hindered phenol structure (excluding the (D1) component) ,
The mass ratio of the (D2) component to the (D1) component ((D2)/(D1)) is 1 or more and 10 or less,
The total amount of the component (D1) and the component (D2) is 85% by mass or more with respect to 100% by mass of the component (D),
The content of component (D) is 4.5% by mass or more and 15% by mass or less with respect to 100% by mass of the flux composition.
Flux composition.

containing the flux composition according to claim 1 and (E) a solder powder,
solder composition. In the solder composition according to claim 2 ,
The solder alloy in the component (E) contains at least one selected from the group consisting of tin, copper, zinc, silver, antimony, lead, indium, bismuth, nickel, gold, cobalt and germanium.
solder composition. A method for manufacturing an electronic substrate for soldering using the solder composition according to claim 2 or 3 ,
A reflow step of placing an electronic component on the solder composition and heating it in a reflow furnace,
A method for manufacturing an electronic substrate, wherein the time to reach the melting temperature in the reflow step is 330 seconds or longer.