JP6895215B2 - Flux composition for flow soldering - Google Patents

Description

The present invention relates to a flux composition for soldering.

As a method of soldering an electronic board and an electronic component, in addition to the so-called reflow soldering method, a method of soldering an electronic component temporarily fixed to the electronic board by contacting it with a jet of molten solder, a so-called flow soldering method. Has also been adopted. In this flow soldering method, for example, a flux composition as described in Patent Document 1 is used before being brought into contact with the jetted molten solder.
On the other hand, with the recent trend toward lead-free solder, solder having a high melting point tends to be used. The most used lead-free solder alloys are tin (Sn) -silver (Ag) -copper (Su) -based solder alloys, so-called SAC-based solder alloys. This SAC-based solder alloy has poor wettability and spread on the oxidized copper foil as compared with the conventional tin-lead eutectic solder. Therefore, in the solder spreading test using the SAC-based solder alloy, there was no flux composition having a flux composition of 80% or more.

Japanese Unexamined Patent Publication No. 8-243787

An object of the present invention is to provide a flux composition for soldering, which has sufficiently excellent solder wetting property even when lead-free solder is used.

In order to solve the above problems, the present invention provides the following flux composition for soldering.
The soldering flux composition of the present invention comprises (A) a rosin-based resin, (B) an activator, (C) a solvent, and (D) an aliphatic carboxylic acid having 12 to 24 carbon atoms and 1 to 4 carbon atoms. It is characterized by containing a higher aliphatic ester composed of the alcohol of.

In the flux composition for soldering of the present invention, the blending amount of the component (D) is preferably 0.1% by mass or more and 5% by mass or less with respect to 100% by mass of the flux composition.

According to the present invention, it is possible to provide a flux composition for soldering having sufficiently excellent solder wetting property even when lead-free solder is used.

The soldering flux composition of the present embodiment (hereinafter, also simply referred to as “flux composition”) is described below as (A) rosin-based resin, (B) activator, (C) solvent and (D) higher fat. It contains a group ester.
In the present specification, the lead-free solder refers to a solder metal or alloy to which lead is not added. However, it is permissible for lead to be present as an unavoidable impurity in the lead-free solder, but in this case, the amount of lead is preferably 300 mass ppm or less.

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

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

The blending amount of the component (A) is preferably 0.5% by mass or more and 20% by mass or less, and more preferably 1% by mass or more and 10% by mass or less with respect to 100% by mass of the flux composition. It is particularly preferable that it is 2% by mass or more and 6% by mass or less. When the blending amount of the component (A) is at least the above lower limit, the generation of bridges and icicles 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 further reduced.

[(B) component]
Examples of the activator include organic acids, non-dissociative activators composed of non-dissociative halogenated compounds, and amine-based activators. One of these activators may be used alone, or two or more thereof may be mixed and used.
Examples of the organic acid include monocarboxylic acids, dicarboxylic acids and the like, as well as other organic acids.
Monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enant acid, capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, tubercrostearic acid , Arakidic acid, behenic acid, lignoseric acid, and glycolic acid.
Examples of the dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, tartaric acid, and diglycolic acid.
Other organic acids include dimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anis acid, citric acid, picolin acid and the like.
In the present embodiment, the component (B) preferably contains succinic acid from the viewpoint of wetting through holes.

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

Amine-based activators include amines (polyamines such as ethylenediamine), amine salts (amines such as trimethylolamine, cyclohexylamine, diethylamine, organic acid salts such as aminoalcohol, and inorganic acid salts (hydrochloride, sulfuric acid, bromide). Hydrogenic acid, etc.)), amino acids (glycine, alanine, aspartic acid, glutamate, and valine, etc.), amide compounds, and the like. Specifically, diphenylguanidine hydrobromide, cyclohexylamine hydrobromide, diethylamine salts (salts, succinates, adipates, sebacates, etc.), triethanolamine, monoethanolamine, and , Hydrobromide of these amines and the like.

The blending amount of the component (B) is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 8% by mass or less with respect to 100% by mass of the flux composition. It is particularly preferable that the content is 2% by mass or more and 5% by mass or less. When the blending amount is at least the above lower limit, the solderability can be improved, while when it is at least the above upper limit, the insulating property of the flux composition can be ensured.

[(C) component]
As the solvent (C) used in this embodiment, a known solvent can be appropriately used. As the component (C), it is preferable to use a water-soluble solvent (C1) having a boiling point of 100 ° C. or lower.
Examples of the component (C1) include ethyl alcohol and isopropyl alcohol. One of these solvents may be used alone, or two or more of these solvents may be mixed and used.

The component (C) is a glycol solvent or a terpene solvent having a boiling point of 120 ° C. or higher and 320 ° C. or lower (preferably 240 ° C. or higher and 320 ° C. or lower) at (C2) 1013 hPa, in addition to a water-soluble solvent having a boiling point of 100 ° C. or lower. May be contained. Such a component (C2) can contribute to the suppression of thermal deterioration of the activator.
Examples of the ( C2 ) component include ethylene glycol monomethyl ether (124 ° C.), triethylene glycol monomethyl ether (249 ° C.), polyethylene glycol monomethyl ether (295 ° C.), triethylene glycol monobutyl ether (271 ° C.), and diethylene glycol monohexyl ether. (259 ° C), Diethylene glycol mono2-ethylhexyl ether (272 ° C), ethylene glycol monophenyl ether (245 ° C), diethylene glycol monophenyl ether (283 ° C), ethylene glycol monobenzyl ether (256 ° C), diethylene glycol monobenzyl ether (25 ° C). 302 ° C), tripropylene glycol monoethyl ether (242 ° C), tripropylene glycol monobutyl ether (274 ° C), propylene glycol monophenyl ether (243 ° C), diethylene glycol dibutyl ether (255 ° C), tetraethylene glycol dimethyl ether (275 ° C). ) And isobornylcyclohexanol (310-318 ° C.) and the like. Among these, tripropylene glycol monobutyl ether, propylene glycol monophenyl ether, diethylene glycol mono2-ethylhexyl ether, and isobornylcyclohexanol are preferable. One of these may be used alone, or two or more thereof may be mixed and used. The temperature described in parentheses is the boiling point of the above solvent.

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, and 80% by mass with respect to 100% by mass of the flux composition. It is particularly preferable that it is% or more and 90% by mass or less. When the blending amount is within the above range, the coatability of the flux composition can be adjusted within an appropriate range.

[(D) component]
The higher aliphatic ester (D) used in the present embodiment is a higher aliphatic ester composed of an aliphatic carboxylic acid having 12 to 24 carbon atoms and an alcohol having 1 to 4 carbon atoms. Since this component (D) is hard to be deactivated even when the activating action is high temperature, the solder wettability when lead-free solder is used can be improved. When the number of carbon atoms of the aliphatic carboxylic acid is 11 or less, the effect of improving the solder wettability is insufficient. On the other hand, aliphatic carboxylic acids having 25 or more carbon atoms are difficult to obtain. Further, when the number of carbon atoms of the alcohol is 5 or more, the effect of improving the solder wettability is insufficient. The aliphatic carboxylic acid preferably has 12 to 18 carbon atoms, and particularly preferably 18. The carbon number of the alcohol is preferably 2 to 4, and particularly preferably 4.
One of these higher aliphatic esters may be used alone, or two or more thereof may be mixed and used.

Here, the aliphatic carboxylic acid may be saturated or unsaturated. In addition, the aliphatic carboxylic acid may have a branch.
Examples of aliphatic carboxylic acids include lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid, arachidic acid, henicosylic acid, behenic acid, tricosylic acid, lignoceric acid, α-linolenic acid, and linoleic acid. , And oleic acid.
Examples of the alcohol include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, tert-butyl alcohol and the like.

The blending amount of the component (D) is preferably 0.1% by mass or more and 5% by mass or less, and preferably 0.2% by mass or more and 3% by mass or less with respect to 100% by mass of the flux composition. More preferably, it is 0.5% by mass or more and 2% by mass or less. When the blending amount is at least the above lower limit, the solder wetting property can be further improved, while when it is at least the above upper limit, the insulation reliability can be maintained.

In addition to the components (A) to (D), the flux composition of the present embodiment contains additives such as a thix agent, an antioxidant, an antifoaming agent, a rust preventive, and a surfactant, if necessary. May be contained. 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.

[Soldering method]
Next, a soldering method using the flux composition of the present embodiment will be described. The soldering method of the present embodiment is a method including a component mounting step, a flux coating step, and a soldering step described below.

In the component mounting process, first, the electronic component is inserted into the electronic board and mounted.
Examples of the electronic board include a printed wiring board.
Electronic components can be inserted into through-holes on an electronic board, and are used in a method of mounting by soldering after insertion (so-called through-hole mounting). Electronic components include integrated circuits, transistors, diodes, resistors and capacitors.

In the flux application step, the above-mentioned flux composition is applied to the soldered surface of the electronic substrate.
As a flux composition coating device, a spray fluxer, a foaming fluxer, or the like can be adopted. Among these, a spray fluxer is preferable from the viewpoint of stability of the coating amount.
From the viewpoint of solderability, the amount of the flux composition applied ^{is preferably 30 mL / m 2} or more and 180 mL / m ² or less, more preferably 40 mL / m ² or more and 150 mL / m 2 or less, and 50 ^{mL / m / m 2.} it is particularly preferred m is ² or more 120 mL / ^{m 2} or less.

In the soldering process, the soldering surface of the electronic board is brought into contact with the molten solder for soldering.
The method of contacting the molten solder is not particularly limited as long as it can contact the molten solder with the electronic substrate. As such a method, for example, a method of contacting with molten solder jetting on an electronic substrate (flow soldering method) may be adopted. Further, a method of bringing the solder bath containing the molten solder into contact with the electronic substrate may be adopted.
The soldering conditions may be appropriately set according to the melting point of the solder. For example, when a Sn—Au—Cu based solder alloy is used, 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). The preheat temperature 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).

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these examples. The materials used in Examples and Comparative Examples are shown below.
(Ingredient (A))
Rosin resin: Product name "China Rosin X", manufactured by Arakawa Chemical Industry Co., Ltd. ((B) component)
Activator A: Succinic acid activator B: Adipic acid activator C: Trans-2,3-dibromo-2-butene-1,4-diol (TDBD), manufactured by Maruzen Yuka Shoji Co., Ltd. ((C1) component)
Solvent A: Isopropyl alcohol ((C2) component)
Solvent B: Tripropylene glycol monobutyl ether (component (D))
Higher fatty acid ester A: Butyl stearate, trade name "Exepearl BS", Shimada Trading Co., Ltd. higher fatty acid ester B: ethyl stearate higher fatty acid ester C: isopropyl stearate higher fatty acid ester D: methyl laurate (other components)
Dibasic acid ester: diisopropyl succinate, manufactured by Maruzen Yuka Shoji Co., Ltd.

[Example 1]
3% by mass of rosin resin, 1.5% by mass of activator A, 0.5% by mass of activator B, 1% by mass of activator C, 0.5% by mass of higher fatty acid ester A, 90.5% by mass of solvent A and 3% by mass of solvent B It was put into a container and mixed to obtain a flux composition.

[Examples 2 to 5 and Comparative Examples 1 to 2]
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 characteristics of the flux composition (solder spread, wetting) were evaluated by the following methods. The results obtained are shown in Table 1.
(1) Solder spread A copper plate (size: 50 mm × 50 mm, thickness: 0.5 mm) is polished with No. 600 water-resistant abrasive paper, further washed with isopropyl alcohol, and then in a dryer at 150 ° C. for 1 hour. The test piece was obtained by subjecting it to the oxidation treatment of.
Next, a 0.05 mL flux composition was applied onto the test piece, and a solder ring (one roll of wire solder having a diameter of φ1.6 mm wound around a rod having a diameter of φ3.2 mm) was placed on the test piece. Place on a ceramic plate. Then, this ceramic plate was placed on a solder bath set at 255 ° C., and the test piece was heated. Then, after the solder was melted, heating was continued for 30 seconds, and the solder was pulled up horizontally and allowed to cool to obtain a sample for evaluation.
For this evaluation sample, the height (H) of the spread solder was measured with a micrometer, and the spread ratio (Sr) was calculated from the following mathematical formula (F1).
Sr = (DH) / D × 100 ... (F1)
D = 1.24V ^1/3 ... (F2)
Sr: Spread rate (%)
H: Height of spread solder (mm)
D: Diameter (mm) when the solder used in the test is regarded as a sphere
V: Mass / Density of Solder Used in Test The test is performed on (i) solder ring 1 and (ii) solder ring 2, respectively.
(I) Solder alloy composition of solder ring 1: Sn3.0Ag0.5Cu
(Ii) Solder alloy composition of solder ring 1: Sn0.3Ag0.7Cu
Then, based on the spread ratio, the solder spread was evaluated according to the following criteria. The spread rate (%) is also shown in Table 1.
〇: The spread rate is 80% or more.
X: The spread rate is less than 80%.
(2) Wet-up A substrate (thickness: 1.6 mm) having through holes with diameters of 1.0 mm and 0.8 mm was subjected to reflow treatment three times to obtain a test piece. The reflow conditions here are a preheat temperature of 150 to 200 ° C. (80 seconds), a time of a temperature of 200 ° C. or higher for 80 seconds, and a peak temperature of 250 ° C.
Next, the flux composition was applied to this test piece with a spray flaxer (applied amount: 110 mL / m ² ), and then flow soldering was performed to obtain a sample for evaluation. The flow soldering conditions here are a preheat temperature of 100 to 120 ° C. (30 to 60 seconds), a solder temperature of 250 ° C., and a solder alloy composition of Sn3.0Ag0.5Cu.
For this evaluation sample, 120 points each of 1.0 mm and 0.8 mm in diameter were observed, and the place where the solder got wet all around the end face of the through hole was regarded as "OK", and the wetting rate was calculated by the following formula (F3). ).
Wetting rate (%) = {(OK number of φ1.0 / 120) + (OK number of φ0.8 / 120)} × 100 ... (F3)
Then, based on the wetting rate, the wetting was evaluated according to the following criteria. The wetting rate (%) is also shown in Table 1.
⊚: The wetting rate is 80% or more.
◯: The wetting rate is 70% or more and 80% or less.
X: The wetting rate is less than 70%.

As is clear from the results shown in Table 1, when the flux composition of the present invention was used (Examples 1 to 5), it was found that all of the solder spread and the wettability were good. Therefore, according to the present invention, it has been confirmed that the solder wetting property is sufficiently excellent even when lead-free solder is used.

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

Claims (2)

It contains (A) a rosin-based resin, (B) an activator, (C) a solvent, and (D) a higher aliphatic ester composed of an aliphatic carboxylic acid having 12 to 24 carbon atoms and an alcohol having 1 to 4 carbon atoms. ,
Amount of the component (C), with respect to the flux composition 100 wt% state, and are 70 wt% to 95 wt% or less,
A flux composition for flow soldering , wherein the blending amount of the component (D) is 0.1% by mass or more and 5% by mass or less with respect to 100% by mass of the flux composition. In the flux composition for flow soldering according to claim 1,
The component (C) contains a water-soluble solvent having a boiling point of 100 ° C. or lower at (C1) 1013 hPa and a glycol-based solvent or a terpene-based solvent having a boiling point of 120 ° C. or higher and 320 ° C. or lower at (C2) 1013 hPa. A characteristic flux composition for flow soldering.