JP7185175B1 - flux - Google Patents

Abstract

A flux capable of suppressing the elution amount of Bi is provided. The flux comprises (A) a rosin-based resin and (B) 0.15% by mass or more of a hydroxycarboxylic acid having no aromatic ring or an unsaturated carboxylic acid having no aromatic ring. Contains a hydroxycarboxylic acid with an absolute value of ΔG of 0.02 or less represented by the formula (1) or an unsaturated carboxylic acid that becomes a hydroxycarboxylic acid with an absolute value of ΔG of 0.02 or less by hydration reaction do. ΔG = G0 in equilibrium configuration - sum of simple substances (organic acid, Bi) G0 (1) G0 = H0 - T (K) x S0 G0: Gibbs energy H0: enthalpy T: temperature S0: entropy [selection diagram] Fig. 2

Description

The present invention relates to a flux containing a rosin resin.

In recent years, there has been an increasing need to lower working temperatures in order to reduce damage to parts and reduce machine power consumption. For this reason, low-melting-point solders have attracted attention, for example, as shown in Patent Document 1. In Patent Document 1, it contains Bi, In and Sn, contains 46% by mass or more and 72% by mass or less of Bi, 26% by mass or more and 54% by mass or less of In, and 2% by mass or less of Sn, and has a melting point of 86 to 111. It has been proposed to provide a solder alloy that has a Also, attention is paid to Sn-58Bi (Sn42Bi58) as a low-temperature eutectic solder.

Japanese Patent Application Laid-Open No. 2022-43721

On the other hand, when solder containing Bi is placed in a high-humidity environment in the presence of flux residue after soldering, there is a risk that the soldered portion will corrode due to elution of Bi.

The present invention has been made in view of these points, and provides a flux capable of suppressing the elution amount of Bi.

[Concept 1]
The flux according to the invention is
(A) a rosin-based resin, and (B) 0.15% by mass or more of a hydroxycarboxylic acid having no aromatic ring or an unsaturated carboxylic acid having no aromatic ring, represented by the following formula (1) A hydroxycarboxylic acid with an absolute value of ΔG of 0.02 or less or an unsaturated carboxylic acid that becomes a hydroxycarboxylic acid with an absolute value of ΔG of 0.02 or less by hydration reaction may be contained.
ΔG = G ⁰ of equilibrium configuration - total G ⁰ of simple substance (organic acid, Bi) (1)
^G0 = ^H0 - T(K) x ^S0
G ⁰ : Gibbs energy H ⁰ : Enthalpy T: Temperature S ⁰ : Entropy

[Concept 2]
The flux according to the invention is
(A) a rosin-based resin, and (B) a carboxylic acid having one or more hydroxy groups at any of the α-, β-, and γ-positions having no aromatic ring of 0.15% by mass or more, or an aromatic ring containing one or more of α,β-unsaturated carboxylic acid, β,γ-unsaturated carboxylic acid and γ,δ-unsaturated carboxylic acid,
The hydroxycarboxylic acid or the unsaturated carboxylic acid may have 4 or more and 12 or less carbon atoms.

[Concept 3]
Fluxes according to concept 1 are carboxylic acids with one or more hydroxy groups in any of the α-, β- and γ-positions that do not have aromatic rings, or α,β-unsaturated carboxylic acids that do not have aromatic rings. , β,γ-unsaturated carboxylic acid and γ,δ-unsaturated carboxylic acid.

[Concept 4]
In a flux according to any one of Concepts 1-3,
(B) as a component, having the unsaturated carboxylic acid,
The number of unsaturated bonds may be 2 or less.

[Concept 5]
In a flux according to any one of Concepts 1-4,
The number of carboxy groups in the hydroxycarboxylic acid or the unsaturated carboxylic acid may be 1 or more and 3 or less.

[Concept 6]
In a flux according to any one of Concepts 1-5,
(B) having the hydroxycarboxylic acid as a component,
The number of hydroxy groups may be 1 or more and 4 or less.

[Concept 7]
In a flux according to any one of Concepts 1-6,
(B) as a component, having the unsaturated carboxylic acid,
The number of hydroxy groups may be 3 or less.

[Concept 8]
In a flux according to any one of Concepts 1-7,
(B) As a component, any one or more of citric acid, malic acid, aconitic acid and tartaric acid may be included.

[Concept 9]
In a flux according to any one of Concepts 1-8,
A solvent may be contained in an amount of 65% by mass or more and 95% by mass or less.

[Concept 10]
The flux according to any one of Concepts 1-9 may be a flux for solders containing Bi.

[Concept 11]
The flux according to any one of concepts 1-10 may be a flux used in a jet soldering apparatus.

According to the present invention, it is possible to provide a flux capable of suppressing the elution amount of Bi.

The figure which showed an example of the aspect by which unsaturated carboxylic acid hydrates and hydroxycarboxylic acid is produced|generated. 4 is a graph showing the results of changing the content of citric acid in the flux in Example 1. FIG. The side view which showed an example of the jet soldering apparatus. FIG. 4 is a side view showing another example of a jet soldering device;

Preferred embodiments of the present embodiment will be described in detail below. "Or" in this embodiment is a concept including "and", for example, A or B indicates either A, B, or both A and B.

The flux of the present embodiment comprises (A) a rosin-based resin, and (B) 0.15% by mass or more of aromatic ring-free α-, β-, and γ-positions containing one or more hydroxyl groups. or one or more of α,β-unsaturated carboxylic acid, β,γ-unsaturated carboxylic acid and γ,δ-unsaturated carboxylic acid having no aromatic ring. Carboxylic acids having one or more hydroxy groups at any of the α-position, β-position and γ-position not having an aromatic ring, or α,β-unsaturated carboxylic acids not having an aromatic ring, β,γ-unsaturated The content of one or more of the saturated carboxylic acid and the γ,δ-unsaturated carboxylic acid relative to the total flux is advantageously 0.2% by mass or more, particularly 1.0% by mass or more. Beneficial (see FIG. 2 below). Carboxylic acids having one or more hydroxy groups at any of the α-position, β-position and γ-position not having an aromatic ring or α,β-unsaturated carboxylic acids not having an aromatic ring, β,γ-unsaturated If the content of one or more of the carboxylic acid and γ,δ-unsaturated carboxylic acid is too high, the flux residue tends to absorb moisture, causing moisture absorption, stickiness, corrosion, etc. Therefore, the upper limit is 5. 0% by weight, more preferably 4.0% by weight, and even more preferably 3.5% by weight. According to the inventors of the present application, the amount of Bi elution could be remarkably suppressed by using such a flux.

As a result of confirmation by the inventors of the present application, it was confirmed that there is a correlation between the Bi elution amount and the absolute value of ΔG calculated by the following formula (1) in the flux containing the rosin resin. . Therefore, from the viewpoint of suppressing the amount of Bi elution, hydroxycarboxylic acid that does not have an aromatic ring with a small absolute value of ΔG calculated by the following formula (1) or becomes hydroxycarboxylic acid by a hydration reaction It will be preferred to use unsaturated carboxylic acids that do not have aromatic rings. In particular, it was confirmed that it is excellent when the absolute value of ΔG is 0.02 or less, and particularly excellent when the absolute value of ΔG is 0.014 or less. The hydroxycarboxylic acid or unsaturated carboxylic acid having such a small absolute value of ΔG has one or more hydroxy groups at any of the α-positions, β-positions and γ-positions that do not have an aromatic ring. or one or more of α,β-unsaturated carboxylic acid, β,γ-unsaturated carboxylic acid and γ,δ-unsaturated carboxylic acid having no aromatic ring.
ΔG = G ⁰ of equilibrium configuration - total G ⁰ of simple substance (organic acid, Bi)
^G0 = ^H0 - T(K) x ^S0 (1)
G ⁰ : Gibbs energy H ⁰ : Enthalpy T: Temperature S ⁰ : Entropy The analysis conditions are as follows, and the analysis was performed using the molecular modeling software "Spartan'20".
・Calculate the -COOH group of the compound in a non-ionized state ・Calculate the G ⁰ of the compound alone and Bi alone ) and calculate the G ⁰ of the equilibrium configuration ・ Calculate the temperature at 25 ° C, which is the standard state

Satisfying any one or more of the following conditions (1) to (5) is a hydroxycarboxylic acid that does not have an aromatic ring or does not have an aromatic ring that becomes a hydroxycarboxylic acid by hydration reaction The unsaturated carboxylic acid is excellent from the viewpoint that the absolute value of ΔG becomes small. Regarding unsaturated carboxylic acids, the absolute value of ΔG does not necessarily decrease, but when water is added, a hydration reaction occurs at the unsaturated bond and a hydroxy group is generated (Fig. 1), the resulting hydroxycarboxylic acid has a small absolute value of ΔG.

(1) The hydroxycarboxylic acid or unsaturated carboxylic acid having no aromatic ring in the component (B) has 4 or more and 12 or less carbon atoms.
(2) It has an unsaturated carboxylic acid as the component (B) and has two or less unsaturated bonds.
(3) The number of carboxy groups in the hydroxycarboxylic acid or unsaturated carboxylic acid having no aromatic ring in component (B) is 1 or more and 3 or less.
(4) It has a hydroxycarboxylic acid as the component (B) and has 1 or more and 4 or less hydroxy groups.
(5) It has an unsaturated carboxylic acid as the component (B) and has 3 or less hydroxy groups.

［リンゴ酸］

［トランスアコニット酸］

［酒石酸］

本実施の形態では、その他のヒドロキシカルボン酸として、例えばＤＬ－２－ヒドロキシ酪酸（ΔＧ＝－０．０１０１９）、ＤＬ－３－ヒドロキシ酪酸（ΔＧ＝－０．０１１６５）、ロイシン酸（ΔＧ＝－０．００８７４）、３－ヒドロキシイソ吉草酸（ΔＧ＝－０．０１０７９）、３－ヒドロキシ－３－メチル吉草酸（ΔＧ＝－０．００８８２）、２，３，４，５－テトラヒドロキシ アジピン酸（ΔＧ＝－０．００５８１）、２－ヒドロキシ－ｎ－オクタン酸（ΔＧ＝－０．００９２１）、１２ヒドロキシステアリン酸（ΔＧ＝－０．００７６６）等を用いることができる。逆に、乳酸（ΔＧ＝－０．０３４５６）、２－ヒドロキシパルミチン酸（ΔＧ＝－０．０２６６７）等はΔＧの絶対値が大きく、好ましいものではない。 As component (B), any one or more of citric acid, malic acid, aconitic acid and tartaric acid may be used. The structural formulas of citric acid, malic acid, transaconitic acid and tartaric acid are as follows. The ΔG for citric acid was −0.00547, the ΔG for malic acid was −0.01377, and the ΔG for tartaric acid was −0.00837.
[citric acid]

[malic acid]

[Transaconitic acid]

[tartaric acid]

In the present embodiment, other hydroxycarboxylic acids include, for example, DL-2-hydroxybutyric acid (ΔG = -0.01019), DL-3-hydroxybutyric acid (ΔG = -0.01165), leucic acid (ΔG = - 0.00874), 3-hydroxyisovaleric acid (ΔG = -0.01079), 3-hydroxy-3-methylvaleric acid (ΔG = -0.00882), 2,3,4,5-tetrahydroxyadipic acid (ΔG=−0.00581), 2-hydroxy-n-octanoic acid (ΔG=−0.00921), 12-hydroxystearic acid (ΔG=−0.00766) and the like can be used. Conversely, lactic acid (ΔG=−0.03456), 2-hydroxypalmitic acid (ΔG=−0.02667) and the like have large absolute values of ΔG and are not preferable.

Organic acids having a hydroxyl group, such as citric acid, malic acid, aconitic acid, and tartaric acid, are often used in water-soluble fluxes, and are expected to be cleaned with a flux cleaning liquid such as water. On the other hand, flux containing rosin resin is generally used without cleaning. The reason for this is that if an organic acid having a hydroxyl group such as citric acid, malic acid, aconitic acid, or tartaric acid is used in a flux containing a rosin resin, the hydroxyl groups in the flux residue will absorb moisture, causing corrosion. It is for the sake of becoming.

As shown below, citric acid is produced when aconitic acid undergoes a hydration reaction, so it is presumed that aconitic acid is changed to citric acid. As the aconitic acid, transaconitic acid may be used.

The flux may be a liquid flux and may contain a solvent. A solvent may be used individually by 1 type, and may be used in mixture of 2 or more types. Examples of solvents include water, alcohol solvents, glycol ether solvents, terpineols and the like. Examples of alcohol solvents include ethanol, 1-propanol, 2-propanol, 1,2-butanediol, isobornylcyclohexanol, 2,4-diethyl-1,5-pentanediol, 2,2-dimethyl- 1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyne-2,5-diol, 2,3-dimethyl-2,3-butanediol, 2 -methylpentane-2,4-diol, 1,1,1-tris(hydroxymethyl)propane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 2,2′-oxybis(methylene)bis( 2-ethyl-1,3-propanediol), 2,2-bis(hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, 1-ethynyl-1-cyclohexanol, 1, 4-cyclohexanediol, 1,4-cyclohexanedimethanol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol and the like. Examples of glycol ether solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, diethylene glycol monohexyl ether (hexyl diglycol), diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, methylpropylene triglycol, butyl Propylene triglycol, triethylene glycol butyl methyl ether, tetraethylene glycol dimethyl ether and the like.

The solvent preferably contains a solvent having a boiling point of 100° C. or less from the viewpoint of increasing volatility in preheating. The solvent having a boiling point of 100° C. or less is preferably an alcohol-based solvent from the viewpoint of solubility of the specific activator. The alcoholic solvent preferably contains 2-propanol.

The solvent content in the flux is preferably 40% by mass or more and 98% by mass or less, more preferably 65% by mass or more and 95% by mass or less, relative to the total amount of the flux (100% by mass). , more preferably 70% by mass or more and 95% by mass or less.

The flux of the present embodiment is used for Sn-50In (50Sn50In), Sn58Bi (42Sn58Bi), Sn57Bi1Ag (42Sn57Bi1Ag), SAC305 (96.5Sn3Ag0.5Cu) solder alloys, etc., but the content of Bi can be reduced. From the point of view that it can be used, it is very beneficial to use it in solders containing Bi such as Sn58Bi and Sn57Bi1Ag (Bi-containing solders). The solder for which the flux of this embodiment is used may be lead-free solder. In addition, in the present embodiment, a solder paste is also provided, and from the viewpoint that the content of Bi can be reduced as described above, solder containing Bi such as Sn58Bi, Sn57Bi1Ag (Bi-containing solder) and flux are included. A solder paste that Further, in this embodiment, substrates, electronic devices, and the like manufactured using the flux and solder paste of this embodiment are also provided.

Examples of rosin-based resins include starting rosins such as gum rosin, wood rosin and tall oil rosin, and derivatives obtained from starting rosins. Derivatives include, for example, purified rosin and modified rosin. Examples of modified rosin include hydrogenated rosin, polymerized rosin, polymerized hydrogenated rosin, disproportionated rosin, disproportionated hydrogenated rosin, acid-modified rosin, rosin ester, acid-modified hydrogenated rosin, and acid-modified hydrogenated rosin. , acid-modified disproportionated rosin, acid anhydride-modified disproportionated rosin, phenol-modified rosin and α,β-unsaturated carboxylic acid-modified products (acrylated rosin, maleated rosin, fumarated rosin, etc.), and purified polymerized rosin , hydrides and disproportions, and purified α,β-unsaturated carboxylic acid modified products, hydrides and disproportions, rosin alcohol, rosin amine, hydrogenated rosin alcohol, rosin ester, hydrogenated rosin glycerin ester, etc. Added rosin esters, rosin soaps, hydrogenated rosin soaps, acid-modified rosin soaps, acrylic acid-modified rosins, acrylic acid-modified hydrogenated rosins, acrylic acid-modified disproportionated rosins, hydrogenated rosin glycerin esters, and the like. These rosin-based resins are used singly or in combination of two or more.

The content of rosin in the flux is preferably 1% by mass or more and 30% by mass or less, more preferably 2% by mass or more and 25% by mass or less, relative to the total amount (100% by mass) of the flux. , more preferably 2% by mass or more and 20% by mass or less. By containing the rosin-based resin in the flux, the effect of improving the heat resistance of the active ingredient can be obtained. If the content of the rosin-based resin is less than 1% by mass of the entire flux, the heat resistance cannot be ensured, and if it exceeds 30% by mass, the substrate becomes extremely sticky after the flux is applied. It is beneficial that the rosin-based resin is 1 to 30% by mass with respect to the entire flux.

The activator contained in the flux of this embodiment is (B) a carboxylic acid having one or more hydroxy groups at any of the α-, β-, and γ-positions having no aromatic ring or having no aromatic ring In addition to one or more of α,β-unsaturated carboxylic acids, β,γ-unsaturated carboxylic acids and γ,δ-unsaturated carboxylic acids, other active agents may be included. Examples of other activators include organic acid-based activators other than (B), amine-based activators, halogen-based activators, organic phosphorus compounds, and the like.

Examples of organic acid surfactants include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, picolinic acid, 2,2-bis(hydroxymethyl)propionic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, nonadecanedioic acid, eicosanedioic acid, 4-tert-butylbenzoic acid, palmitic acid, 2-ethylhexyl Mono-2-ethylhexyl phosphonate, dimer acid, trimer acid, hydrogenated dimer acid which is a hydrogenated product of dimer acid with hydrogen added, hydrogenated trimer acid which is a hydrogenated product of trimer acid with hydrogen added, etc. be done. Examples of amine-based activators include rosin amines, azoles, guanidines, alkylamine compounds, aminoalcohol compounds and the like. Examples of halogen-based activators include amine hydrohalides and organic halogen compounds other than amine hydrohalides. Examples of aminoalcohol compounds include N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, monoisopropanolamine and the like.

Amine hydrohalides include, for example, cyclohexylamine hydrobromide, hexadecylamine hydrobromide, stearylamine hydrobromide, ethylamine hydrobromide, 1,3-diphenylguanidine odor Hydrochloride, ethylamine hydrochloride, stearylamine hydrochloride, diethylaniline hydrochloride, diethanolamine hydrochloride, 2-ethylhexylamine hydrobromide, pyridine hydrobromide, isopropylamine hydrobromide, diethylamine odor hydrochloride, dimethylamine hydrobromide, dimethylamine hydrochloride, rosinamine hydrobromide, 2-ethylhexylamine hydrochloride, isopropylamine hydrochloride, cyclohexylamine hydrochloride, 2-pipecoline hydrobromide , 1,3-diphenylguanidine hydrochloride, dimethylbenzylamine hydrochloride, hydrazine hydrate hydrobromide, dimethylcyclohexylamine hydrochloride, trinonylamine hydrobromide, diethylaniline hydrobromide, 2- Diethylaminoethanol hydrobromide, 2-diethylaminoethanol hydrochloride, ammonium chloride, diallylamine hydrochloride, diallylamine hydrobromide, diethylamine hydrochloride, triethylamine hydrobromide, triethylamine hydrochloride, hydrazine monohydrochloride, hydrazine dihydrochloride, hydrazine monohydrobromide, hydrazine dihydrobromide, pyridine hydrochloride, aniline hydrobromide, butylamine hydrochloride, hexylamine hydrochloride, n-octylamine hydrochloride, dodecylamine hydrochloride salt, dimethylcyclohexylamine hydrobromide, ethylenediamine dihydrobromide, rosinamine hydrobromide, 2-phenylimidazole hydrobromide, 4-benzylpyridine hydrobromide, L-glutamic acid salt, N-methylmorpholine hydrochloride, betaine hydrochloride, 2-pipecoline hydroiodide, cyclohexylamine hydroiodide, 1,3-diphenylguanidine hydrofluoride, diethylamine hydrofluoride, 2- ethylhexylamine hydrofluoride, cyclohexylamine hydrofluoride, ethylamine hydrofluoride, rosinamine hydrofluoride, cyclohexylamine tetrafluoroborate, and dicyclohexylamine tetrafluoroborate; be done.

Examples of organic halogen compounds include tetrabromomethane, 1,1,2,2-tetrabromobutane, 1,2-dibromo-2-butene, 2,3-dibromo-1-propanol, 1,2-dibromo-2, 3-butanediol, 2,3-dibromo-2-butene-1,4-diol, 2,2-bis(bromomethyl)-1,3-propanediol, triallyl isocyanurate hexabromide, 1-bromo-2- butanol, 1-bromo-2-propanol, 3-bromo-1-propanol, 3-bromo-1,2-propanediol, 1,4-dibromo-2-butanol, 1,3-dibromo-2-propanol, 2 ,3-dibromo-1-propanol, 2,3-dibromo-1,4-butanediol, chloroalkanes which are organic chloro compounds, chlorinated fatty acid esters, het acid, het acid anhydride and the like.

Examples of organic phosphorus compounds include acidic phosphates, acidic phosphonates, and acidic phosphinates. Acidic phosphates include, for example, methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, monobutyl acid phosphate, butyl acid phosphate, dibutyl acid phosphate, butoxyethyl acid phosphate, and 2-ethyl acid phosphate. xyl acid phosphate, bis(2-ethylhexyl) phosphate, monoisodecyl acid phosphate, diisodecyl acid phosphate, lauryl acid phosphate, isotridecyl acid phosphate, stearyl acid phosphate, oleyl acid phosphate, beef tallow Phosphate, coconut oil phosphate, isostearyl acid phosphate, alkyl acid phosphate, tetracosyl acid phosphate, ethylene glycol acid phosphate, 2-hydroxyethyl methacrylate acid phosphate, dibutylpyrophosphate acid phosphate and the like. . Acidic phosphonates include, for example, 2-ethylhexyl (2-ethylhexyl) phosphonate, n-octyl (n-octyl) phosphonate, n-decyl (n-decyl) phosphonate, n-butyl (n-butyl) phosphonate, isodecyl Examples thereof include alkyl (alkyl) phosphonates such as (isodecyl) phosphonate, diethyl (p-methylbenzyl) phosphonate and the like. Acidic phosphinic acid esters include, for example, phenyl-substituted phosphinic acids. Phenyl-substituted phosphinic acids include, for example, phenylphosphinic acid and diphenylphosphinic acid.

The flux may contain surfactants. Examples of surfactants include nonionic surfactants and weak cationic surfactants.
Examples of nonionic surfactants include polyethylene glycol, polyethylene glycol-polypropylene glycol copolymers, aliphatic alcohol polyoxyethylene adducts, aromatic alcohol polyoxyethylene adducts, and polyhydric alcohol polyoxyethylene adducts. be done.
Examples of weak cationic surfactants include terminal diamine polyethylene glycol, terminal diamine polyethylene glycol-polypropylene glycol copolymer, aliphatic amine polyoxyethylene adduct, aromatic amine polyoxyethylene adduct, polyvalent amine polyoxy Ethylene adducts can be mentioned.
Examples of surfactants other than the above include polyoxyalkylene acetylene glycols, polyoxyalkylene glyceryl ethers, polyoxyalkylene alkyl ethers, polyoxyalkylene esters, polyoxyalkylene alkylamines, polyoxyalkylene alkylamides, and the like. .

The flux of this embodiment may be the flux used in the jet soldering apparatus 100 (see FIGS. 3 and 4). Since the amount of Bi elution often becomes a problem in an apparatus such as the jet soldering apparatus 100 that jets a large amount of flux, it is difficult to use the flux of the present embodiment as the flux used in the jet soldering apparatus 100. Very informative.

As the jet soldering apparatus 100, for example, those configured as shown in FIGS. 3 and 4 can be employed. As an example, the jet soldering apparatus 100 may have a storage tank 110 that stores the molten solder S, and a first supply section 120 and a second supply section 130 that supply the molten solder S. The first supply unit 120 includes a first casing 121 , a first pump 141 as a first driving unit, and one or more first pumps 141 for ejecting the molten solder S receiving driving force from the first pump 141 . and a supply port 125 . The second supply unit 130 has a second housing 131, a second pump 146 that is a second driving unit, and a driving force from the second pump 146 to eject the molten solder S. Alternatively, it may have a plurality of second supply ports 135 . The molten solder S supplied from the first supply port 125 and the molten solder S supplied from the second supply port 135 are mixed, and the mixed molten solder S flows through the first supply port 125 and the second supply port 135. In between, it may be a mode not to separate from the substrate transported by the transport unit (see FIG. 4). In this case, the upper surface of the mixed molten solder S is located at the lower end of the transport rail 6 that transports the board in the full length region along the board transport direction between the first supply port 125 and the second supply port 135 . It cannot be positioned lower than In addition, a mode may be adopted in which a portion where the molten solder S drops downward is not provided between the first supply port 125 and the second supply port 135 along the board transfer direction A (see FIG. 4). When the molten solder S supplied from the first supply port 125 and the molten solder S supplied from the second supply port 135 separate and fall toward the stored molten solder S, a large amount of oxygen and will touch. For this reason, it is presumed that oxides such as dross are generated more, but there is no place between the first supply port 125 and the second supply port 135 where the molten solder S drops downward. Such an inconvenience can be prevented by adopting the aspect. Therefore, by adopting such an aspect while using the flux provided in the present embodiment, it can be expected that the generation of oxides such as dross can be significantly suppressed.

The flux (50 μl) of Examples 1 to 7 and Comparative Examples 1 to 12 shown in Tables 1 to 3 was added to a 0.3 g disk-shaped Sn58Bi solder on a copper plate (30 mm long × 30 mm wide × 0.3 mm thick). applied to the alloy. A spreading test was performed on a copper plate by heating the fluxed Sn58Bi solder alloy on the copper plate at 180° C. for 30 seconds. After the spreading test on the copper plate, the residual flux on the copper plate was dissolved in acetone and collected as a sample. The collected sample was analyzed using an ICP mass spectrometer (ICP-MS) (RF power: 1600 W) manufactured by Agilent Technologies to measure the eluted amount of Bi.

As a method for recovering the sample, the sample after spreading on the copper plate was immersed in 5 g of acetone. After covering with paraffin paper, ultrasonic waves were applied for 30 minutes, and acetone and those eluted in acetone (metal ions) were collected as samples.

Tables 1 to 3 show the test results (Bi elution amount) with the ICP mass spectrometer. When the amount of Bi elution is large, the corrosion of Bi contained in the solder alloy is accelerated. On the other hand, when the amount of Bi elution is small, the corrosion of Bi contained in the solder alloy can be suppressed. It will be possible. It was confirmed that in the embodiment according to the embodiment, the elution amount of Bi can be suppressed to a small amount, and the corrosion of Bi contained in the solder alloy can be suppressed.

The results of compositions containing the same compounds as in Example 1, but with varying amounts of citric acid, are shown in FIG. The content of 2-propanol was reduced as the content of citric acid was increased. As is clear from the embodiment shown in FIG. 2, it was confirmed that the elution amount of Bi could be stably suppressed when the content was 0.2% by mass or more.

比較例の中では比較例２で示す態様においてＢｉ溶出量が最も小さくなっており、０．３ｍｇ／Ｌとなっている。これに対して、実施例１においては、クエン酸の含有量が０．２％であり、比較例２の２，４－ジヒドロキシ安息香酸の含有量の１０分の１ではあるものの、Ｂｉ溶出量を０．１８とすることができた。つまり、比較例２の２，４－ジヒドロキシ安息香酸の含有量の１０分の１でありながらも、Ｂｉの溶出量を６０％程度にすることができ、非常に優れた効果を得ることができた。また、実施例であるクエン酸、リンゴ酸、トランスアコニット酸及び酒石酸の中でも、クエン酸及びリンゴ酸を用いることが特に有益であることも確認することができた。

Among the comparative examples, the Bi elution amount is the smallest in the embodiment shown in Comparative Example 2, which is 0.3 mg/L. On the other hand, in Example 1, the content of citric acid was 0.2%, which was 1/10 of the content of 2,4-dihydroxybenzoic acid in Comparative Example 2, but the amount of Bi elution was could be 0.18. In other words, even though the content of 2,4-dihydroxybenzoic acid in Comparative Example 2 is 1/10, the elution amount of Bi can be made about 60%, and a very excellent effect can be obtained. rice field. It was also confirmed that among the examples of citric acid, malic acid, transaconitic acid and tartaric acid, the use of citric acid and malic acid is particularly beneficial.

As shown in Example 7 and Comparative Example 12 in Table 3 below, even in a flux having a compound composition different from that of Examples 1 to 6 and Comparative Examples 1 to 11, the elution amount of Bi was significantly reduced in the embodiment. It was confirmed that it can be suppressed to

Claims (9)

A flux for solder containing Bi,
(A) a rosin-based resin,
(B) 0.15 % by mass or more of any one or more of citric acid, malic acid and tartaric acid, and
(C) containing 65% by mass or more and 95% by mass or less of a solvent,
A flux that does not contain lactic acid, salicylic acid and hydroxybenzoic acid . A flux for solder containing Bi,
(A) a rosin-based resin; and (B) a flux containing 0.15 % by mass or more of aconitic acid . 2. The flux of claim 1, containing malic acid or tartaric acid. 2. The flux according to claim 1, wherein the total content of citric acid, malic acid and tartaric acid is 5.0 mass % or less. 5. The flux according to claim 1, wherein the total content of citric acid, malic acid and tartaric acid is 1.0 mass % or more. 3. The flux according to claim 2, wherein the content of aconitic acid is 5.0% by mass or less. 3. The flux according to claim 1, comprising 1% by mass or more and 30% by mass or less of a rosin resin. 3. The flux according to claim 1, which contains a solvent in an amount of 70% by mass or more. 3. The flux according to claim 1, which is used in a jet soldering apparatus.

Images