JP6560279B2 - Flux composition for local soldering and soldering method - Google Patents

Description

  The present invention relates to a local soldering flux composition and a soldering method.

  One method for soldering an electronic substrate and an electronic component is a local soldering method. This local soldering method is a method of performing soldering by covering a portion of an electronic board that is not to be soldered with a pallet mask and bringing the solder into contact with molten solder only at the target portion. In this local soldering method, for example, a flux composition as described in Patent Document 1 is used before contact with molten solder. As a flux composition used for this local soldering method, not only solderability but also flux residue is required not to be deposited on the pallet mask. If the flux residue is likely to be deposited on the pallet mask, the flux residue deposited on the pallet mask must be washed frequently, resulting in a decrease in productivity. Moreover, the flux residue deposited on the pallet mask may adhere to the electronic substrate and impair the performance of the substrate.

JP-A-8-243787

In the flux composition as described in Patent Document 1, there is a problem that the flux residue is easily deposited on the pallet mask because of the large amount of rosin in the composition. On the other hand, when the amount of rosin is reduced, problems such as bridges and icicles occur, and solderability tends to decrease. Furthermore, when the blending amount of the activator is increased to supplement the solderability, there is a problem that the insulation reliability of the flux residue is lowered. Thus, the solderability and the difficulty of depositing the flux residue are in a trade-off relationship, and conventionally it has been difficult to achieve both of them.
Furthermore, in the local soldering method, the solder is less likely to adhere due to the influence of the thickness of the pallet mask as compared with the flow soldering method of the whole surface soldering. Therefore, in the local soldering method, the jet wave of the solder bath is increased, the jet velocity of the solder bath is increased, or the conveyor speed when contacting the molten solder is decreased. In such a case, it becomes difficult to separate the soldered portion from the molten solder, and as a result, problems such as bridges and icicles tend to occur.

  Accordingly, the present invention provides a flux composition for local soldering, which is excellent in solderability and hardly deposits flux residue on a pallet mask when performing local soldering, and a soldering method using the same. With the goal.

In order to solve the above-mentioned problems, the present invention provides the following flux composition for local soldering and a soldering method.
The flux composition for local soldering of the present invention contains (A) a rosin resin, (B) an activator, and (C) a solvent, wherein the component (A) is (A1) has a softening point of 120. A first rosin resin having a softening point of 90 ° C. or less, and a first rosin resin having a softening point of 90 ° C. or less, and a first rosin resin having a softening point of 90 ° C. or less; The mass ratio ((A2) / (A1)) of the component (A2) to the component (A1) is 2.5 or more and 10 or less, and the blending amount of the component (A) is a flux composition. It is 7 mass% or more and 20 mass% or less with respect to 100 mass% of things.

In the flux composition for local soldering of this invention, it is preferable that the said (B) component contains the salt of (B1) amines and a fluorine compound.
In the flux composition for local soldering of this invention, it is preferable that the said (B) component further contains (B2) organic acid.
In the local soldering flux composition of the present invention, the component (A2) is preferably a partially hydrogenated rosin.
In the local soldering flux composition of the present invention, the mass ratio ((A2) / (A1)) of the component (A2) to the component (A1) is preferably 3.5 or more and 6 or less .
The soldering method of the present invention includes a step of attaching the electronic substrate to a pallet mask provided with an opening at a place where the electronic component is soldered, and inserting the electronic component into the electronic substrate. The method comprising: applying the local soldering flux composition to a soldering surface; and bringing the soldering surface of the electronic substrate into contact with molten solder and soldering It is.

The reason why the flux composition for local soldering of the present invention is excellent in solderability when the local soldering is performed and the flux residue is not easily deposited on the pallet mask is not necessarily clear. Guesses as follows.
That is, in the local soldering flux composition of the present invention, (A) the rosin resin includes (A1) a first rosin resin having a softening point of 120 ° C. or higher, (A2) a hydrogenated rosin and an inhomogeneous resin. A second rosin resin that is at least one selected from the group consisting of fluorinated rosins and has a softening point of 90 ° C. or lower is used in combination. And it can suppress that a flux residue accumulates on a pallet mask etc. by (A2) component. The reason for this is that the fluidity of the flux residue increases due to the presence of the component (A2), and when the soldered part comes into contact with the solder bath and then leaves the solder bath, the flux residue tends to flow down to the solder bath side. The inventors speculate. On the other hand, the components (A1) and (A2) are used in combination, and the amount of rosin in the flux composition itself is not reduced. Therefore, unlike the case where the amount of rosin is reduced, problems such as bridges and icicles hardly occur, and solderability does not deteriorate. As described above, the present inventors speculate that the effects of the present invention are achieved.

  ADVANTAGE OF THE INVENTION According to this invention, when performing local soldering, it is excellent in solderability and can provide the flux composition for local soldering which a flux residue does not accumulate on a pallet mask, and the soldering method using the same.

It is the schematic which shows the electronic substrate and electronic component which are used for this embodiment. It is the schematic which shows the pallet mask used for this embodiment. In this embodiment, it is the schematic which shows the state which attached the electronic board | substrate to the pallet mask. It is sectional drawing which shows the IV-IV cross section of FIG. It is a graph which shows the relationship between the adhesion amount (unit: g) of the flux residue measured in Example 4 and Comparative Example 1, and the repetition frequency.

  The flux composition for local soldering of the present embodiment (hereinafter also simply referred to as “flux composition”) contains (A) a rosin resin, (B) an activator, and (C) a solvent, which will be described below. is there.

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

In this embodiment, the component (A) is at least one selected from the group consisting of (A1) a first rosin resin having a softening point of 120 ° C. or higher, and (A2) a hydrogenated rosin and a disproportionated rosin. It is necessary to contain a second rosin resin which is a seed and has a softening point of 90 ° C. or lower. Thus, by using together (A1) component and (A2), when performing local soldering, it is difficult to deposit a flux residue on a pallet mask. Furthermore, since the softening point of the rosin resin can be adjusted by using the components (A1) and (A2) in combination, the occurrence of unsolder due to the rosin resin itself becoming an obstacle during local soldering is prevented. it can.
Examples of the component (A1) include rosin resins having a softening point of 120 ° C. or higher among the components (A). From the viewpoint of solderability, the softening point of the component (A1) is preferably 130 ° C. or higher. The softening point can be measured by the ring and ball method.

The component (A2) is at least one selected from the group consisting of a hydrogenated rosin and a disproportionated rosin among the components (A), and a rosin resin having a softening point of 90 ° C. or less. Can be mentioned. Of the hydrogenated rosins, partially hydrogenated rosin is more preferably used from the viewpoint that the flux residue is more difficult to deposit on the pallet mask.
Furthermore, the softening point of the component (A2) is preferably 85 ° C. or less, and more preferably 80 ° C. or less, from the viewpoint that the flux residue is more likely to flow.

  In addition, as means for adjusting the softening point of the component (A1) and the component (A2), adjusting the polymerization degree of rosin (the higher the polymerization degree, the higher the softening point), Changing the modification method (for example, modification with acrylic acid or maleic acid tends to increase the softening point), adjusting the molecular weight of rosin (the higher the molecular weight, the higher the softening point) And rosin is subjected to hydrogenation reaction, and rosin is subjected to esterification reaction or transesterification reaction.

  In this embodiment, the mass ratio ((A2) / (A1)) of the component (A2) to the component (A1) is preferably 2 or more and 10 or less, and preferably 2.5 or more and 8 or less. More preferably, it is 3 or more and 6 or less, and further preferably 3.5 or more and 5.5 or less. If the mass ratio is equal to or higher than the lower limit, the flux residue can be more difficult to deposit on the pallet mask. On the other hand, if the mass ratio is less than or equal to the above upper limit, the occurrence of bridges and icicles can be more reliably suppressed.

  The blending amount of the component (A) 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. It is even more preferable that the content is not less than 12% by mass and not more than 12% by mass. (A) If the compounding quantity of a component is more than the said minimum, generation | occurrence | production of a bridge | bridging and icicle can be suppressed more reliably. On the other hand, if the blending amount of the component (A) is not more than the above upper limit, the flux residue can be reduced and the flux residue deposited on the pallet mask can be reduced.

[Component (B)]
Examples of the (B) activator used in the present embodiment include salts of amines and fluorine compounds, organic acids, non-dissociative activators composed of non-dissociable halogenated compounds, and amine-based activators. These activators may be used individually by 1 type, and may mix and use 2 or more types. Moreover, it is preferable that this (B) component contains the salt of (B1) amines and a fluorine compound. By this (B1) component, it is easy to separate the soldered portion from the molten solder, and bridges and icicles can be more reliably suppressed.

The amine in the component (B1) may be a chain amine (eg, n-butylamine) or a cyclic amine (eg, piperidine). Examples of the fluorine compound in the component (B1) include boron trifluoride and borohydrofluoric acid.
The component (B1) may be a complex having piperidine (which may have a substituent) as a ligand. Examples of the metal of the complex include boron, copper, and aluminum.
Examples of the component (B1) include boron trifluoride piperidine complex and n-butylamine borofluoride. Among these, boron trifluoride piperidine complex salt is particularly preferable.

  The blending amount of the component (B1) is preferably 0.01% by mass or more and 5% by mass or less, and 0.05% by mass or more and 2% by mass or less with respect to 100% by mass of the flux composition. More preferably, the content is 0.1% by mass or more and 1% by mass or less. If a compounding quantity is more than the said minimum, bridge | bridging and icicle can be suppressed more reliably. On the other hand, if it is below the said upper limit, a piperidine complex salt can be melt | dissolved in a flux composition, and the stability as a liquid is securable.

The component (B) preferably further contains (B2) an organic acid from the viewpoint of solderability.
Examples of the component (B2) include other organic acids in addition to monocarboxylic acid and dicarboxylic acid.
Monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, tuberculostearic acid Arachidic acid, behenic acid, lignoceric acid, glycolic acid and the like.
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.
Examples of other organic acids include dimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anisic acid, citric acid, and picolinic acid.

  The blending amount of the component (B2) is preferably 0.1% by mass or more and 5% by mass or less, and 0.5% by mass or more and 4% by mass or less with respect to 100% by mass of the flux composition. Is more preferable, and 1% by mass or more and 3% by mass or less is particularly preferable. If the amount is greater than or equal to the lower limit, the solderability can be further improved. On the other hand, if the amount is less than or equal to the upper limit, the insulation of the flux composition can be secured.

The component (B) may contain an active agent (component (B3)) other than the component (B1) and the component (B2) as necessary. Examples of the component (B3) include a non-dissociative activator composed of a non-dissociable halogenated compound, and an amine-based activator other than the component (B1).
Examples of the non-dissociable activator comprising the non-dissociable halogenated compound include non-salt organic compounds in which halogen atoms are bonded by a covalent bond. The halogenated compound may be a compound formed by covalent bonding of chlorine, bromine and fluorine, such as chlorinated, brominated and fluoride, but any two or all of chlorine, bromine and fluorine may be used. The compound which has the following covalent bond may be sufficient. In order to improve the solubility in an aqueous solvent, 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. 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 The compound similar to these is mentioned. Examples of the halogenated carboxyl include 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, 5-iodoanthranilic acid, and the like, 2-chlorobenzoic acid, and 3- Examples thereof include carboxyl chloride such as chloropropionic acid, brominated carboxyl such as 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid, and 2-bromobenzoic acid, and similar compounds.

  Examples of amine-based activators other than the component (B1) include amines (polyamines such as ethylenediamine), amine salts (ethylamine, diethylamine, trimethylolamine, cyclohexylamine, amines such as diethylamine, and organic acids such as amino alcohols) Examples thereof include salts and inorganic acid salts (hydrochloric acid, sulfuric acid, hydrobromic acid, etc.), amino acids (glycine, alanine, aspartic acid, glutamic acid, valine, etc.), amide compounds, and the like. Specifically, ethylamine hydrobromide, diphenylguanidine hydrobromide, cyclohexylamine hydrobromide, diethylamine salts (such as hydrochloride, succinate, adipate, and sebacate), tris Examples include ethanolamine, monoethanolamine, and hydrobromides of these amines.

  The blending amount of the component (B) is preferably 0.5% by mass to 10% by mass and more preferably 1% by mass to 8% by mass with respect to 100% by mass of the flux composition. It is particularly preferably 2% by mass or more and 5% by mass or less. If the amount is greater than or equal to the lower limit, the solderability can be further improved. On the other hand, if the amount is less than or equal to the upper limit, the insulation of the flux composition can be secured.

[Component (C)]
As the solvent (C) used in the present embodiment, a known solvent can be appropriately used. As the component (C), a water-soluble solvent having a boiling point of 100 ° C. or lower is preferably used. Examples of the component (C) include ethyl alcohol and isopropyl alcohol. These solvents may be used alone or in combination of two or more.

  The blending amount of the component (C) is preferably 70% by mass or more and 95% by mass or less, more preferably 75% by mass or more and 92% by mass or less, with respect to 100% by mass of the flux composition. It is particularly preferable that the content is not less than mass% and not more than 90 mass%. If a compounding quantity is in the said range, the applicability | paintability of a flux composition can be adjusted to an appropriate range.

  In addition to the component (A), the component (B) and the component (C), the flux composition of the present embodiment includes a thixotropic agent, an antioxidant, an antifoaming agent, a rust preventive agent, if necessary. And additives such as surfactants may be contained. As a compounding quantity of these additives, it is preferable that they are 0.01 mass% or more and 5 mass% or less with respect to 100 mass% of flux compositions.

[Soldering method]
Next, the soldering method of this embodiment will be described. The soldering method of this embodiment is a soldering method using the flux composition of this embodiment described above. And the soldering method of this embodiment is a method provided with the attachment process demonstrated below, a flux application | coating process, and a soldering process.

In the attaching step, first, the electronic substrate 1 and the electronic component 2 as shown in FIG. 1 and the pallet mask 3 provided with the opening 31 at the location where the electronic component 2 as shown in FIG. prepare.
Then, as shown in FIG. 3, the electronic component 2 is inserted into the electronic substrate 1 and the electronic substrate 1 is attached to the pallet mask 3.
Examples of the electronic substrate 1 include a printed wiring board.
The electronic component 2 can be inserted into the through hole of the electronic substrate 1 and is used by a method of mounting by soldering after insertion (so-called through hole mounting). Examples of the electronic component 2 include an integrated circuit, a transistor, a diode, a resistor, and a capacitor.
The pallet mask 3 is provided with an opening 31 where the electronic component 2 is soldered. That is, as shown in FIGS. 3 and 4, the pallet mask 3 is provided with an opening 31 at a location where the electronic component 2 is soldered. The soldering surface 1 </ b> A of the electronic substrate 1 can contact the molten solder at the opening 31, but cannot contact the molten solder at portions other than the opening 31.
In this attachment step, the electronic component 2 may be inserted into the electronic substrate 1 first, or the electronic substrate 1 may be attached to the pallet mask 3 first.

In the flux application step, the aforementioned flux composition is applied to the soldering surface 1A of the electronic substrate 1 as shown in FIG.
As a flux composition coating device, a spray fluxer, a foaming fluxer, or the like can be employed. Among these, a spray fluxer is preferable from the viewpoint of coating amount stability.
From the viewpoint of solderability, the application amount of the flux composition is preferably 30 mL / m ² or more and 150 mL / m ² or less, more preferably 40 mL / m ² or more and 120 mL / m ² or less, and 50 mL / m ^2. it is particularly preferred m is ² or more 100 mL / ^{m 2} or less.

In the soldering process, soldering is performed by bringing the soldering surface 1A of the electronic substrate 1 into contact with the molten solder.
In a portion other than the opening 31 of the pallet mask 3, the molten solder does not contact the soldering surface 1 </ b> A of the electronic substrate 1. On the other hand, in the opening 31 of the pallet mask 3, the molten solder contacts the soldering surface 1 </ b> A of the electronic substrate 1. Therefore, it can solder locally only in the location which solders the electronic component 2.
The method for bringing the molten solder into contact is not particularly limited as long as it is a method capable of bringing the molten solder into contact with the electronic substrate 1. As such a method, for example, a method (flow soldering method) of contacting the molten solder jetted onto the electronic substrate 1 may be employed. Moreover, you may employ | adopt the method of making the electronic tank 1 contact the solder tank containing molten solder.
What is necessary is just to set the conditions of soldering suitably according to melting | fusing point of solder. For example, when using a Sn—Au—Cu-based solder alloy, the temperature of the molten solder may be set to 230 ° C. or higher and 280 ° C. or lower (preferably 250 ° C. or higher and 270 ° C. or lower). Further, the preheating may be set to a heating temperature of 80 ° C. or higher and 130 ° C. or lower (preferably 90 ° C. or higher and 120 ° C. or lower).

EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these examples. In addition, the material used in the Example and the comparative example is shown below.
((A1) component)
First rosin resin A: hydrogenated acid modified rosin (softening point: about 130 ° C.), trade name “Pine Crystal KE-604”, Arakawa Chemical Industries, Ltd. first rosin resin B: polymerized rosin (softening point: about 140 ° C.), trade name “polymerized rosin 140”, manufactured by Arakawa Chemical Industries, Ltd. (component (A2))
Second rosin resin A: partially hydrogenated rosin (softening point: about 80 ° C.), trade name “Stevelite Resin E”, second rosin resin B manufactured by Eastman Chemical Japan: partially hydrogenated rosin (softening point: About 80 ° C.), trade name “RHR-301M”, second rosin resin C manufactured by Maruzen Oil Chemical Co., Ltd .: disproportionated rosin (softening point: about 80 ° C.), trade name “Longis R”, manufactured by Arakawa Chemical Industries, Ltd. Second rosin resin D: fully hydrogenated rosin (softening point: about 80 ° C.), trade name “Foral AX”, manufactured by Eastman Chemical Japan (component (B1))
Activator A: Boron trifluoride piperidine complex salt (component (B2))
Activator B: Succinic acid activator C: Palmitic acid (component (B3))
Activator D: Ethylamine hydrobromide Activator E: trans-2,3-dibromo-2-butene-1,4-diol (component (C))
Solvent: Isopropyl alcohol

[Example 1]
First rosin resin A 1% by mass, second rosin resin A 10% by mass, activator A 0.4% by mass, activator B 0.2% by mass, activator C 2% by mass, activator D 0.9% by mass, activator E 0.5 mass% and 85 mass% of solvent were put into a container and mixed to obtain a flux composition.

[Examples 2 to 12]
A flux 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 1-3]
A flux 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 flux composition>
The properties of the flux composition (adhesion of flux residue, solderability, copper plate corrosivity, storage stability) were evaluated by the following methods. The obtained results are shown in Table 1.
(1) Adhesion of flux residue After applying 0.02 mL of flux composition to a ceramic plate (size: 25 mm × 25 mm, thickness: 1.6 mm) whose mass has been measured in advance, a solder bath (stationary Solder bath, solder alloy composition: Sn / 3.0Ag / 0.5Cu, solder bath temperature: 265 ° C.) for 10 seconds, and then the ceramic plate is taken out. This operation was repeated 5 times, the mass of the ceramic plate at that time was measured, and the amount of adhesion of the flux residue adhering to the ceramic plate (unit: g) was calculated.
For Example 4 and Comparative Example 1, FIG. 5 shows the relationship between the measured adhesion amount of the flux residue (unit: g) and the number of repetitions every time the above operation is repeated five times.
Moreover, after repeating said operation 20 times, the adhesion amount (unit: g) of the flux residue adhering to the ceramic board was computed. And according to the following reference | standard, the adhesiveness of the flux residue was evaluated.
(Circle): The adhesion amount of a flux residue is 0.02 g or less.
(Triangle | delta): The adhesion amount of a flux residue is more than 0.02g and 0.03g or less.
X: The adhesion amount of a flux residue is more than 0.03g.
(2) Solderability Pallet with an opening provided at a place where soldering is performed on an evaluation board (Tamura evaluation board TSTB, size: 150 mm × 200 mm, thickness: 1.6 mm, number of soldering points: 1032 places) Attached to the mask. Then, it soldered to the evaluation board | substrate attached to the pallet mask on the following soldering conditions.
(Soldering conditions)
Soldering device: “HC33-36NF” manufactured by Tamura Corporation
Flux coating device: spray fluxer (“TAF33-12PV” manufactured by Tamura Corporation)
Flux application amount: 70 mL / m ²
Conveyor speed: 1m / min
Preheat temperature: 100 ° C
Solder bath temperature: 265 ° C
Alloy composition of solder: Sn / 3.0Ag / 0.5Cu
And the evaluation board | substrate after soldering was observed with the magnifier, and solderability was evaluated according to the following reference | standard.
○: There is no generation of unsolder, the generation of bridges is 39 or less, and the occurrence of icicles is 5 or less.
Δ: There is no generation of unsolder, but the generation of bridges is 40 or more and 49 or less, or the occurrence of icicles is 6 or more and 9 or less.
X: The occurrence of unsolder is present, the occurrence of bridges is 50 or more, or the occurrence of icicles is 10 or more.
(3) Copper plate corrosivity The copper plate corrosivity was evaluated according to the following criteria by the method described in JIS Z 3197-1986.
○: Pass x: Fail (4) Preservability The flux composition was left in an environment at a temperature of −15 ° C. for 72 hours, and the appearance was visually observed. And the preservability of the flux composition was evaluated according to the following criteria.
○: There is no generation of crystals.
X: Crystal is generated.

As is apparent from the results shown in Table 1, when the flux composition of the present invention is used (Examples 1 to 12), all of the adhesiveness of the flux residue, solderability, copper plate corrosivity and storage stability are all obtained. Was found to be good. Therefore, when performing local soldering, it was confirmed that the solderability was excellent and the flux residue was not easily deposited on the pallet mask.
On the other hand, when any one or more of the (A1) component, the (A2) component, and the (B) component is not contained (Comparative Examples 1 to 3), either the adhesiveness of the flux residue or the solderability Was confirmed to be insufficient.

  The flux composition for local soldering of the present invention can be suitably used for local soldering using a pallet mask.

DESCRIPTION OF SYMBOLS 1 ... Electronic substrate 1A ... Soldering surface 2 ... Electronic component 3 ... Pallet mask 31 ... Opening

Claims (6)

(A) containing a rosin resin, (B) an activator, and (C) a solvent,
The component (A) is at least one selected from the group consisting of (A1) a first rosin resin having a softening point of 120 ° C. or higher, and (A2) a hydrogenated rosin and a disproportionated rosin, A second rosin resin having a softening point of 90 ° C. or less ,
The mass ratio ((A2) / (A1)) of the component (A2) to the component (A1) is 2.5 or more and 10 or less,
The local soldering flux composition, wherein the blending amount of the component (A) is 7% by mass to 20% by mass with respect to 100% by mass of the flux composition. In the local soldering flux composition according to claim 1,
The said (B) component contains the salt of (B1) amines and a fluorine compound. The flux composition for local soldering characterized by the above-mentioned. In the local soldering flux composition according to claim 2,
The component (B) further contains (B2) an organic acid. A flux composition for local soldering, wherein: In the flux composition for local soldering of any one of Claims 1-3,
The component (A2) is a partially hydrogenated rosin. A flux composition for local soldering, wherein: In the flux composition for local soldering of any one of Claims 1-4,
The mass ratio ((A2) / (A1)) of the component (A2) to the component (A1) is 3.5 or more and 6 or less.
A flux composition for local soldering characterized by the above. A step of attaching the electronic substrate to a pallet mask provided with an opening at a place where soldering of the electronic component is performed while inserting the electronic component into the electronic substrate;
Applying the local soldering flux composition according to any one of claims 1 to 5 to the soldering surface of the electronic substrate;
A process of performing soldering by bringing the soldering surface of the electronic substrate into contact with molten solder; and
A soldering method comprising:

Images