JP2020192597A - flux - Google Patents

Abstract

To provide a flux for soldering a solder alloy which sufficiently improves solder wettability and has excellent stability in long-term storage.SOLUTION: A flux for soldering a solder alloy includes a chlorendic acid ester, where the content of the chlorendic acid ester is more than 0 mass% and 5 mass% or less based on the flux total and the chlorendic acid ester is one or more kinds selected from the group comprising a chlorendic acid monomethyl ester, a chlorendic acid monoethyl ester, a chlorendic acid mono-isopropyl ester, a chlorendic acid monoethylene glycol ester, and a chlorendic acid dimethyl ester.SELECTED DRAWING: None

Description

The present invention relates to a flux for soldering a solder alloy.

Fixing and electrical connection of electronic components in electronic devices, such as mounting electronic components on printed circuit boards, is commonly performed by soldering, which is the most cost effective and reliable.
Commonly used methods for this type of soldering include the flow soldering method, in which the printed circuit board and electronic components are brought into contact with the molten solder for soldering, and solder in the form of solder paste, solder preform or solder balls. This is a reflow soldering method in which remelting is performed in a reflow furnace and soldering is performed.

In this soldering, flux, which is an auxiliary agent that facilitates the adhesion of solder to the printed circuit board and electronic components, is used. Flux has (1) metal surface cleaning action (action of chemically removing the oxide film on the metal surface of printed substrates and electronic parts to clean the surface so that soldering is possible), and (2) re-cleaning. Antioxidant action (action to cover the cleaned metal surface during soldering to block contact with oxygen and prevent the metal surface from being reoxidized by heating), (3) interfacial tension lowering action (melting) It has many useful functions such as reducing the surface tension of the solder and increasing the wettability of the metal surface by the solder).

In soldering a printed circuit board by the flow soldering method, flux (post-flux) is applied to the soldered portion before or after mounting electronic components. After that, the printed circuit board after the post-flux is applied is passed over the solder jetted in the flow soldering apparatus to perform flow soldering.

As a flux used for soldering by the conventional flow soldering method, Patent Document 1 contains 0.2 to 4% by mass of at least one compound selected from a base resin, an activator, an acidic phosphoric acid ester and a derivative thereof. A non-cleaning type resin-based flux for lead-free solder containing the amount of the above has been proposed.
Patent Document 2 describes that the generation of bridges and balls during soldering can be suppressed by a flux containing both an activator containing a chlorine atom and an organic phosphorus compound in a specific ratio.
Patent Document 3 describes that a rosin-based resin and a flux containing a specific activator can sufficiently suppress dewetting and solder bridging during soldering even when lead-free solder is used. ..

International Publication No. 2008/072654 Japanese Patent No. 6322881 Japanese Unexamined Patent Publication No. 2013-126671

However, it cannot be said that the fluxes described in Patent Documents 1 to 3 are sufficiently improved in solder wettability when used in a solder alloy, and there is also a problem in stability during long-term storage.

In view of the above circumstances, it is an object of the present invention to provide a flux for soldering a solder alloy, which has sufficiently improved solder wettability and excellent stability during long-term storage.

As a result of diligent research to solve the above problems, the present inventors have found that the above problems can be solved by using a flux containing a chlorendate, and have completed the present invention. That is, the present invention is as follows.

[1]
Flux containing chlorendate for soldering solder alloys.
[2]
The flux according to the above [1], wherein the content of the chlorendate is more than 0% by mass and 5% by mass or less based on the entire flux.
[3]
The chlorendic acid ester is at least one selected from the group consisting of chlorendic acid monomethyl ester, chlorendic acid monoethyl ester, chlorendic acid monoisopropyl ester, chlorendic acid monoethylene glycol ester, and chlorendic acid dimethyl ester [1]. ] Or the flux according to [2].
[4]
The flux according to any one of the above [1] to [3], further containing a solvent.
[5]
The flux according to the above [4], wherein the solvent is 2-propanol.
[6]
The flux according to any one of the above [1] to [5], wherein the soldering is flow soldering.
[7]
A method for manufacturing a bonded body, which comprises a step of soldering a solder alloy to the surface of the substrate treated with the flux according to any one of [1] to [6] above to form a bonded body.
[8]
The manufacturing method according to the above [7], wherein the soldering is flow soldering.
[9]
A bonded body obtained by the production method according to the above [8] or [9].
[10]
Flux activator containing chlorendate.

According to the present invention, it is possible to provide a flux for soldering a solder alloy, which has sufficiently improved solder wettability and is also excellent in stability during long-term storage.

Hereinafter, embodiments of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail, but the present invention is not limited thereto, and various modifications can be made without departing from the gist thereof. Is.

[flux]
The flux for soldering the solder alloy of the present embodiment contains a chlorendate. Chlorendic acid ester functions as a flux activator. By using the flux of the present embodiment, the wettability of the solder alloy can be sufficiently improved. Soldering can be used for both flow soldering and reflow soldering, but it is preferable to use it for flow soldering because the effect of the present invention becomes more remarkable.

The content of the chlorendate is preferably more than 0% by mass and 5% by mass or less, more preferably more than 0% by mass and 1% by mass or less, and further preferably 0.2% by mass or more with respect to the entire flux. It is 0.7% by mass or less, and particularly preferably 0.3% by mass or more and 0.6% by mass or less. When the content of the chlorendate is more than 0% by mass, the solder wettability and the storage stability tend to be improved. On the other hand, the upper limit of the content of the chlorendate is not particularly limited, but when it exceeds 5% by mass, the active component in the residue increases, so that moisture absorption tends to occur easily. As a result, the insulation resistance value is lowered, the reliability is lowered, and the residue may be sticky due to hygroscopicity. Therefore, it is preferably 5% by mass or less.

The chlorendic acid ester is not particularly limited, and for example, chlorendate monoester such as chlorendic acid monomethyl ester, chlorendic acid monoethyl ester, chlorendic acid monoisopropyl ester, chlorendic acid monoethylene glycol ester; chlorend such as chlorendic acid dimethyl ester. Acid diester and the like can be mentioned. Among these, from the viewpoint of flux activity and compatibility, a monoester in which a carboxylic acid remains is preferable, and an isopropyl ester is particularly preferable.

In addition, as the chlorendate, compounds such as a chlorendate dimer represented by the following formula (6) and a chlorendate multimer in which two or more chlorendates are condensed or bonded via alcohol or the like are also available. included.

(In the formula, R indicates a linear or branched alkylene group, alkylene glycol group, oxyalkylene group which may be substituted.)

The carbon number of the alkylene group, the alkylene glycol group, and the oxyalkylene group represented by R is not particularly limited, but is preferably 1 to 54, and more preferably 2 to 36.

The chlorendate also includes various isomers of the above-mentioned compounds (structural isomers, optical isomers, etc.) and salts of the above-mentioned compounds (amine salts, etc.).

As the chlorendate, one type may be used alone, or two or more types may be used in combination.

In addition, the various chlorendic acid esters described above can be produced by using known methods.

The flux in the present embodiment may contain chlorendic acid and / or anhydrous chlorendic acid in addition to the chlorendic acid ester. The total content of chlorendic acid and chlorendic anhydride is preferably 5% by mass or less, more preferably 2% by mass or less, still more preferably 1% by mass or less, and particularly preferably 0% by mass, based on the total flux. %. If the content of chlorendic acid and chlorendic anhydride is too high, the stability of the flux during long-term storage tends to decrease.

The flux of the present embodiment may further contain an optional component in addition to the chlorendate. Optional components include, for example, solvents, rosins, activators, matting agents and the like.

Examples of the solvent include water, alcohol-based solvents, glycol ether-based solvents, and terpineols. Examples of the alcohol-based solvent include 2-propanol, ethanol, 1,2-butanediol, isobornylcyclohexanol, and the like. 2,4-Diethyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexin-2 , 5-diol, 2,3-dimethyl-2,3-butanediol, 1,1,1-tris (hydroxymethyl) ethane, 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, bis [2 , 2,2-Tris (hydroxymethyl) ethyl] ether, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, erythritol, Treitol, guayacol glycerol ether, 3,6 Included are −dimethyl-4-octin-3,6-diol, and 2,4,7,9-tetramethyl-5-decine-4,7-diol.
Examples of the glycol ether-based solvent include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, 2-methylpentane-2,4-diol, diethylene glycol monohexyl ether, diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, and hexyl. Examples thereof include diglycol and tetraethylene glycol dimethyl ether.
Among the above, an alcohol solvent is preferable from the viewpoint of volatility. Further, 2-propanol is preferable from the viewpoint of suppressing esterification of rosin, an organic acid as an activator and the like with a solvent.
As the solvent, one type may be used alone, or two or more types may be used in combination.

In the case of the flux for flow soldering, the content of the solvent is preferably 75 to 94% by mass, more preferably 80 to 92% by mass, and further preferably 85 to 90% by mass with respect to the entire flux. Is. In the case of flux for reflow soldering, the content of the solvent is preferably 20 to 75% by mass, more preferably 25 to 55% by mass, and further preferably 30 to 50% by mass with respect to the entire flux. Is.

Examples of rosins include acid-modified rosins, purified rosins, hydrogenated rosins, disproportionated rosins, rosin esters, and polymerized rosins. Rosin is a non-volatile component contained in pine resin of Pinaceae plants. Examples of the rosin include tall rosin, gum rosin, and wood rosin. Acid-modified rosin is a rosin treated with acid. The acid-modified rosin may be hydrogenated. Examples of the acid-modified rosin include acrylic acid-modified rosin, acrylic acid-modified hydrogenated rosin, maleic acid-modified rosin, and maleic acid-modified hydrogenated rosin. One type of rosin may be used alone, or two or more types may be used in combination. Since the flux contains rosin, the wettability of the solder alloy tends to be improved.

In the case of a flux for flow soldering, the rosin content is preferably 3 to 18% by mass, more preferably 6 to 15% by mass, still more preferably 9 to 12% by mass, based on the total flux. Is. In the case of flux for reflow soldering, the rosin content is preferably 0 to 65% by mass, more preferably 5 to 60% by mass, and even more preferably 20 to 50% by mass with respect to the total flux. Is.
By setting the rosin content within the above range, the wettability of the solder alloy tends to be further improved.

Activators include, for example, organic acids, halogen-based activators (eg, organic halogen compounds and amine halide hydrolates), amines, and organophosphorus compounds (eg, phosphonic acid esters and phenyl-substituted phosphinic acids) Can be mentioned. As the activator, one type may be used alone, or two or more types may be used in combination. Since the flux contains an activator, the wettability of the solder alloy can be further improved.

Examples of organic acids include adipic acid, azelaic acid, eicosandioic acid, citric acid, glycolic acid, succinic acid, salicylic acid, diglycolic acid, dipicolinic acid, dibutylaniline diglycolic acid, suberic acid, sebacic acid, and thioglycolic acid. , Telephthalic acid, dodecanedioic acid, parahydroxyphenylacetic acid, picolinic acid, phenylsuccinic acid, phthalic acid, fumaric acid, maleic acid, malonic acid, lauric acid, benzoic acid, tartaric acid, glutaric acid, palmitic acid, tris isocyanurate ( 2-carboxyethyl), 1,3-cyclohexanedicarboxylic acid, 2,2-bis (hydroxymethyl) propionic acid, 2,2-bis (hydroxymethyl) butanoic acid, 2,3-dihydroxybenzoic acid, 2,4- Diethylglutaric acid, 2-quinolincarboxylic acid, 3-hydroxybenzoic acid, malic acid, p-anisic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, dimer acid, hydrogenated dimer acid, Examples thereof include trimeric acid and hydrogenated trimeric acid.

Examples of the organic halogen compound include 1,2,4,5-tetrabromobenzene, trans-2,3-dibromo-2-butene-1,4-diol, and 2,3-dibromo-1,4-butanediol. , 2,3-Dibromo-1-propanol, 2,3-dichloro-1-propanol, 1,1,2,2-tetrabromoethane, 2,2,2-tribromoethanol, pentabromoethane, tetrabromide Carbon, 2,2-bis (bromomethyl) -1,3-propanediol, meso-2,3-dibromosuccinic acid, chloroalkane, chlorinated fatty acid ester, n-hexadecyltrimethylammonium bromide, triallyl isocyanurate 6 Bromide, 2,2-bis [3,5-dibromo-4- (2,3-dibromopropoxy) phenyl] propane, bis [3,5-dibromo-4- (2,3-dibromopropoxy) phenyl] sulfone, Examples thereof include ethylene bispentabromobenzene, 2-chloromethyloxylane, and bromide bisphenol A type epoxy resin.

Examples of the amine halide hydrochloride include boron trifluoride piperidine, stearylamine hydrochloride, diethylaniline hydrochloride, diethanolamine hydrochloride, 2-ethylhexylamine hydrobromide, pyridine hydrobromide, and the like. Isopropylamine Hydrochloride, Cyclohexylamine Hydrochloride, diethylamine Hydrochloride, Monoethylamine Hydrochloride, 1,3-diphenylguanidine Hydrochloride, Dimethylamine Hydrochloride , Dimethylamine hydrochloride, rosinamine hydrobromide, 2-ethylhexylamine hydrochloride, isopropylamine hydrochloride, cyclohexylamine hydrochloride, 2-pipecholine hydrobromide, 1,3-diphenylguanidine hydrochloride, dimethylbenzyl Amin hydrochloride, hydrazine hydrate hydrobromide, dimethylcyclohexylamine hydrochloride, trinonylamine hydrobromide, diethylaniline hydrobromide, 2-diethylaminoethanol hydrobromide, 2-diethylaminoethanol Hydrochloride, ammonium chloride, diallylamine hydrochloride, diallylamine hydrobromide, monoethylamine hydrochloride, monoethylamine hydrobromide, diethylamine hydrochloride, triethylamine hydrobromide, triethylamine hydrochloride, hydrazine monohydrochloride, Hydrazin dihydrochloride, hydrazine monobromide, hydrazine dibromide, pyridine hydrochloride, aniline hydrobromide, butylamine hydrochloride, hexylamine hydrochloride, n-octylamine hydrochloride, dodecylamine Hydrochloride, dimethylcyclohexylamine hydrobromide, ethylenediamine dihydrobromide, rosinamine hydrobromide, 2-phenylimidazole hydrobromide, 4-benzylpyridine hydrobromide, L-glutamic acid Hydrochloride, N-methylmorpholine hydrochloride, betaine hydrochloride, 2-pipecholine hydroiodide, cyclohexylamine hydroiodide, 1,3-diphenylguanidine hydrofluoride, diethylamine hydrofluoride, 2 -Ethylhexylamine Hydrochloride Hydrochloride, Cyclohexylamine Hydrochloride Hydrochloride, Ethylamine Hydrochloride Hydrochloride, Rodinamine Hydrochloride Hydrochloride, Cyclohexylamine Tetrafluoroborate, and Dicyclohexylamine Tetrafluoroborate. Be done.

Examples of amines include aliphatic amines, aromatic amines, aminoalcohols, azoles, amino acids, guanidine, and hydrazide.
Examples of aliphatic amines include dimethylamine, ethylamine, 1-aminopropane, isopropylamine, trimethylamine, allylamine, n-butylamine, diethylamine, sec-butylamine, tert-butylamine, N, N-dimethylethylamine, isobutylamine, and Cyclohexylamine can be mentioned.
Examples of aromatic amines include aniline, N-methylaniline, diphenylamine, N-isopropylaniline, and p-isopropylaniline.
Examples of amino alcohols include 2-aminoethanol, 2- (ethylamino) ethanol, diethanolamine, diisopropanolamine, triethanolamine, N-butyldiethanolamine, triisopropanolamine, N, N-bis (2-hydroxyethyl). -N-cyclohexylamine, N, N, N', N'-tetrax (2-hydroxypropyl) ethylenediamine, and N, N, N', N'', N''-pentakis (2-hydroxypropyl) diethylenetriamine Can be mentioned.
Examples of azoles include imidazole, 3,5-dimethylpyrazole, benzotriazole, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methyl. Imidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-un Decylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimerite, 1-cyanoethyl-2-phenylimidazolium trimerite Tate, 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl-s-triazine, 2,4-diamino-6- [2'-undecylimidazolyl- (1')] -Ethyl-s-triazine, 2,4-diamino-6- [2'-ethyl-4'-methylimidazolyl- (1')]-ethyl-s-triazine, 2,4-diamino-6- [2' -Methylimidazolyl- (1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5 -Hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo [1,2-a] benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazoline, epoxy -Imidazole adduct, 2-methylbenzoimidazole, 2-octylbenzoimidazole, 2-pentylbenzoimidazole, 2- (1-ethylpentyl) benzoimidazole, 2-nonylbenzoimidazole, 2- (4-thiazolyl) benzoimidazole, and Benzoimidazole can be mentioned.
Amino acids include, for example, alanine, arginine, asparagine, aspartic acid, cysteine hydrochloride, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine monohydrochloride, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, Examples include valine, β-alanine, γ-aminobutyric acid, δ-aminovaleric acid, ε-aminohexanoic acid, ε-caprolactam, and 7-aminoheptanoic acid.

Phosphonate esters include, for example, 2-ethylhexyl (2-ethylhexyl) phosphonate, n-octyl (n-octyl) phosphonate, n-decyl (n-decyl) phosphonate, and n-butyl (n-butyl) phosphonate. Be done.

Examples of the phenyl-substituted phosphinic acid include phenylphosphinic acid and diphenylphosphinic acid.

The content of the activator is preferably 0.1 to 12.0% by mass, more preferably 0.3 to 8.0% by mass, still more preferably 0.5 to 4% by mass, based on the total flux. It is 0.0% by mass. By setting the content of the activator within the above range, the wettability of the solder alloy tends to be further improved.

Examples of the matting agent include palmitic acid. As the matting agent, one type may be used alone, or two or more types may be used in combination. When the flux contains a matting agent, it is possible to matte the joint portion of the joint and facilitate the visual inspection of the portion.

The polish is preferably 0.01 to 4.0% by mass, more preferably 0.05 to 3.0% by mass, still more preferably 0.1 to 2.% of the total flux. It is 0% by mass. By keeping the content of the polish in the above range, it tends to be possible to further facilitate the visual inspection of the joint portion of the joint.

[Solder alloy]
The flux of the present embodiment can be used for both flow soldering and reflow soldering, but is preferably used for flow soldering from the viewpoint of solder wettability.
As the solder alloy used for flow soldering, a solder alloy having a known composition can be used. Specifically, Sn-Ag alloy, Sn-Cu alloy, Sn-Ag-Cu alloy, Sn-In alloy, Sn-Pb alloy, Sn-Bi alloy, Sn-Ag-Cu-Bi alloy, and the above alloy composition. Examples thereof include alloys in which Ag, Cu, In, Ni, Co, Sb, Ge, P, Fe, Zn, Ga and the like are further added.

As is an element capable of suppressing yellowing due to oxidation of the solder surface after soldering. Since As has low reactivity with flux and is a noble element with respect to Sn, it is presumed that it can exert an effect of suppressing thickening. If As is less than 25 mass ppm, the thickening suppressing effect cannot be sufficiently exhibited. The lower limit of the As content is 25 mass ppm or more, preferably 50 mass ppm or more, and more preferably 100 mass ppm or more. On the other hand, if the amount of As is too large, the wettability of the solder alloy deteriorates. The upper limit of the As content is 300 mass ppm or less, preferably 250 mass ppm or less, and more preferably 200 mass ppm or less.

Bi and Pb have low reactivity with flux, and can impart a thickening suppressing effect to a solder paste for reflow soldering. Further, these elements are elements that can suppress deterioration of wettability due to As because the liquidus temperature of the solder alloy is lowered and the viscosity of the molten solder is reduced.

If at least one element of Bi and Pb is present, deterioration of wettability due to As can be suppressed. When the solder alloy according to the present embodiment contains Bi, the lower limit of the Bi content is 0 mass ppm or more, preferably 25 mass ppm or more, more preferably 50 mass ppm or more, and further preferably 75 mass ppm or more. It is mass ppm or more, particularly preferably 100 mass ppm or more, and most preferably 250 mass ppm or more. When the solder alloy according to the present embodiment contains Pb, the lower limit of the Pb content is 0 mass ppm or more, preferably 25 mass ppm or more, more preferably 50 mass ppm or more, and further preferably 75 mass ppm or more. It is mass ppm or more, particularly preferably 100 mass ppm or more, and most preferably 250 mass ppm or more.

On the other hand, if the content of these elements is too large, the solidus temperature is remarkably lowered, so that ΔT, which is the temperature difference between the liquidus temperature and the solidus temperature, becomes too wide. If ΔT is too wide, the liquid phase Bi and Pb will be concentrated because a high melting point crystal phase having a low content of Bi and Pb is precipitated in the solidification process of the molten solder. After that, when the temperature of the molten solder is further lowered, the low melting point crystal phase having a high concentration of Bi and Pb is segregated. Therefore, the mechanical strength of the solder alloy and the like are deteriorated. In particular, since the crystal phase having a high Bi concentration is hard and brittle, segregation in the solder alloy significantly reduces the mechanical strength and the like.

From this point of view, when the solder alloy according to the present embodiment contains Bi, the upper limit of the Bi content is 25,000 mass ppm or less, preferably 10,000 mass ppm or less, and more preferably 1000 mass ppm or less. Yes, more preferably 600 mass ppm or less, and particularly preferably 500 mass ppm or less. When the solder alloy according to the present embodiment contains Pb, the lower limit of the Pb content is 8000 mass ppm or less, preferably 5100 mass ppm or less, more preferably 5000 mass ppm or less, still more preferably. It is 1000 mass ppm or less, particularly preferably 850 mass ppm or less, and most preferably 500 mass ppm or less.

The solder alloy according to this embodiment preferably satisfies the following equation (1).

275 ≦ 2As + Bi + Pb (1)
In the above formula (1), As, Bi, and Pb each represent the content (mass ppm) in the alloy composition.

As, Bi and Pb are all elements that have an effect of suppressing thickening. Suppression of thickening It is preferable that the total of these is 230 mass ppm or more. In the formula (1), the As content is doubled because As has a higher effect of suppressing thickening than Bi and Pb.

If the formula (1) is less than 275, the thickening suppressing effect tends not to be sufficiently exhibited. The lower limit of the equation (1) is 275 or more, preferably 300 or more, more preferably 700 or more, and further preferably 900 or more. On the other hand, the upper limit of (1) is not particularly limited from the viewpoint of the thickening suppressing effect, but is preferably 25200 or less, more preferably 15200 or less, from the viewpoint of setting ΔT in a suitable range. It is more preferably 10200 or less, particularly preferably 8200 or less, and most preferably 5300 or less.

The following equations (1a) and (1b) are obtained by appropriately selecting the upper limit and the lower limit from the above preferred embodiments.

275 ≦ 2As + Bi + Pb ≦ 25200 (1a)
275 ≦ 2As + Bi + Pb ≦ 5300 (1b)
In the above formulas (1a) and (1b), As, Bi, and Pb each represent the content (mass ppm) in the alloy composition.

The solder alloy according to this embodiment preferably satisfies the following equation (2).

0 <2.3 × 10 ^-4 × Bi + 8.2 × 10 ^-4 × Pb ≦ 7 (2)
In the above formula (2), Bi and Pb each represent the content (mass ppm) in the alloy composition.

Bi and Pb suppress the deterioration of wettability due to the inclusion of As, but if the content is too large, ΔT increases, so strict control is required. In particular, in an alloy composition containing Bi and Pb at the same time, ΔT tends to increase. In the present embodiment, the increase in ΔT can be suppressed by defining the total of the values obtained by multiplying the contents of Bi and Pb by a predetermined coefficient. In equation (2), the coefficient of Pb is larger than the coefficient of Bi. This is because Pb has a larger contribution to ΔT than Bi, and even if the content is slightly increased, ΔT is significantly increased.

The solder alloy having the formula (2) of 0 does not contain both Bi and Pb elements, and the deterioration of wettability due to the inclusion of As cannot be suppressed. The lower limit of the equation (2) is more than 0, preferably 0.02 or more, more preferably 0.03 or more, further preferably 0.05 or more, and particularly preferably 0.06 or more. , Most preferably 0.11 or more. On the other hand, if the equation (2) exceeds 7, the temperature range of ΔT becomes too wide, so that the crystal phase having a high concentration of Bi and Pb segregates during solidification of the molten solder, and the mechanical strength and the like deteriorate. The upper limit of (2) is 7 or less, preferably 6.56 or less, more preferably 6.40 or less, further preferably 5.75 or less, and even more preferably 4.18 or less. , Especially preferably 2.30 or less, and most preferably 0.90 or less.

The following equation (2a) is obtained by appropriately selecting the upper limit and the lower limit from the above preferred embodiments.

0.02 ≤ 2.3 x 10 ^-4 x Bi + 8.2 x 10 ^-4 x Pb ≤ 0.9 (2a)
In the above formula (2a), Bi and Pb each represent the content (mass ppm) in the alloy composition.

Ag is an arbitrary element capable of forming Ag ₃ Sn at the crystal interface to improve the mechanical strength of the solder alloy and the like. In addition, Ag is an element whose ionization coefficient is noble with respect to Sn, and when it coexists with As, Pb, and Bi, it promotes the effect of suppressing thickening. The Ag content is preferably 0 to 4%, more preferably 0.5 to 3.5%, and even more preferably 1.0 to 3.0%.

Cu is an optional element that can improve the joint strength of solder joints. Further, Cu is an element whose ionization coefficient is noble with respect to Sn, and when it coexists with As, Pb, and Bi, it promotes the effect of suppressing thickening of these elements. The Cu content is preferably 0 to 0.9%, more preferably 0.1 to 0.8%, and even more preferably 0.2 to 0.7%.

The rest of the solder alloy according to this embodiment is Sn. In addition to the above-mentioned elements, unavoidable impurities may be contained. Even if it contains unavoidable impurities, it does not affect the above-mentioned effects. Further, as will be described later, even if an element not contained in the present embodiment is contained as an unavoidable impurity, the above-mentioned effect is not affected. If the content of In is too large, ΔT spreads, so if it is 1000 mass ppm or less, the above-mentioned effect is not affected.

[Solder paste]
The contents of the solder alloy and the flux in the solder paste are not limited, and for example, the solder alloy may be 5 to 95% by mass and the flux may be 5 to 95% by mass.

The solder paste according to this embodiment preferably contains zirconium oxide powder. Zirconium oxide can suppress an increase in the viscosity of the paste due to aging. It is presumed that this is because the zirconium oxide is contained so that the oxide film thickness on the surface of the solder powder is maintained in the state before being put into the flux. Details are unknown, but it is inferred as follows. Normally, the active component of the flux has a slight activity even at room temperature, so that the surface oxide film of the solder powder becomes thin due to reduction, which causes the powders to aggregate with each other. Therefore, it is presumed that by adding the zirconium oxide powder to the solder paste, the active component of the flux reacts preferentially with the zirconium oxide powder, and the oxide film on the surface of the solder powder is maintained to such an extent that it does not aggregate.

In order to fully exert such effects, the content of the zirconium oxide powder in the solder paste is preferably 0.05 to 20.0% with respect to the total mass of the solder paste. When it is 0.05% or more, the above-mentioned action and effect can be exhibited, and when it is 20.0% or less, the content of the metal powder can be secured, and the thickening prevention effect can be exhibited. The content of zirconium oxide is preferably 0.05 to 10.0%, and the more preferable content is 0.1 to 3%.

The particle size of the zirconium oxide powder in the solder paste is preferably 5 μm or less. When the particle size is 5 μm or less, the printability of the paste can be maintained. The lower limit is not particularly limited, but may be 0.5 μm or more. For the particle size, an SEM photograph of the zirconium oxide powder was taken, and the diameter equivalent to the projected circle was obtained by image analysis for each powder of 0.1 μm or more, and the average value was used.

The shape of zirconium oxide is not particularly limited, but if it has a different shape, the contact area with the flux is large and there is an effect of suppressing thickening. When it is spherical, good fluidity can be obtained, so that excellent printability as a paste can be obtained. The shape may be appropriately selected according to the desired characteristics.

The method for producing the soldering flux and the solder paste of the present embodiment is not limited, and the raw materials can be produced by mixing the raw materials simultaneously or sequentially by any method.

[Joint body and its manufacturing method]
The method for producing a bonded body of the present embodiment is a step of soldering a solder alloy to the surface of a substrate treated with a flux containing a chlorendate ester to form a bonded body (hereinafter, referred to as a “bonding step”). including.

Details of the flux and the solder alloy used in the manufacturing method in the present embodiment are as described in the above items of [Flux] and [Solder alloy].

The production method in the present embodiment may further include a step of treating the surface of the substrate with a flux containing a chlorendate (hereinafter, referred to as a “pretreatment step”) prior to the joining step.

The treatment method in the pretreatment step and the joining method in the joining step are not particularly limited, and a method generally practiced in the present technical field can be adopted. Soldering is preferably performed by flow soldering.

The bonded body contains a substrate, a solder alloy soldered to the surface of the substrate, and a flux residue. Examples of the substrate include a printed wiring board. Examples of the joint include a printed circuit board in which electronic components are attached to a printed wiring board.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the technical scope of the present invention is not limited thereto.

(Evaluation)
(1) Evaluation of solder wettability The wettability of the fluxes prepared in Examples and Comparative Examples was evaluated based on the zero cross time measured by Menisco. Menisco conditions are as follows.
-Solid sample: Copper plate (width 5 mm x length 25 mm x thickness 0.5 mm; no oxidation treatment, etc.)
-Solder tank temperature: 280 ° C (solder alloy: Sn-3Ag-0.5Cu)
・ Immersion speed: 20 mm / sec
・ Immersion depth: 5 mm
・ Measurement time: 10 sec
-Flux treatment: Immerse a copper plate in flux (immersion depth approx. 10 mm)
The evaluation criteria for the wetting rate are as follows.
〇 〇: Zero cross time 3 seconds or less 〇: Zero cross time 6 seconds or less ×: Zero cross time more than 6 seconds

(2) Storage stability The storage stability of the fluxes prepared in Examples and Comparative Examples was evaluated. Storage stability was evaluated by the rate of decrease in acid value after humidified storage. Humidification conditions are as follows.
-Initial acid value: Calculate the initial acid value by the sum of the acid value of each material x the blending ratio.-Humidification conditions: 50 ° C, 5 hours The evaluation criteria for storage stability are as follows.
〇: Acid value is within 30% of initial acid value ×: Acid value is reduced by more than 30% from initial acid value

The fluxes of Examples A1 to 56 and Comparative Examples A1 to 3 were prepared with the compositions shown in the table below.
The numerical value of each component in the table below represents the mass% of each component with respect to the total mass of the flux, and the "remaining" in the "solvent" column indicates that the solvent is added to the total of the components other than the solvent. This means that the total amount of flux is 100% by mass.

In the table, the chlorendic acid monomethyl ester represents a compound represented by the following formula (1), the chlorendic acid monoethyl ester represents a compound represented by the following formula (2), and the chlorendate monoisopropyl ester represents the following compound. The compound represented by the formula (3) is shown, the chlorendic acid monoethylene glycol ester shows the compound represented by the following formula (4), and the chlorendate dimethyl ester shows the compound represented by the following formula (5). Shown. Each compound contains its isomer (structural isomer / stereoisomer).

[Solder alloy study]
The flux prepared in Example 40 and the solder alloy having the alloy composition shown in Tables 8 and 9 and having a size (particle size distribution) satisfying the symbol 4 in the powder size classification (Table 2) in JIS Z 3284-1: 2004. Was mixed to prepare a solder paste. The mass ratio of the flux to the solder alloy is flux: solder powder = 11:89. The liquidus temperature and solidus temperature of the solder powder were measured. Furthermore, the wettability was evaluated using the solder paste immediately after production. The details are as follows.

(3) Evaluation of wettability (paste)
Each solder paste immediately after production was printed on a Cu plate, heated in an N2 atmosphere in a reflow furnace from 25 ° C. to 260 ° C. at a heating rate of 1 ° C./s, and then cooled to room temperature. Wetability was evaluated by observing the appearance of the solder bumps after cooling with an optical microscope. When the unmelted solder powder was not observed, it was evaluated as "◯", and when the unmelted solder powder was observed, it was evaluated as "x".

(4) ΔT
For the solder alloy before mixing with the flux, DSC measurement was performed using SII Nanotechnology Co., Ltd., model number: EXSTAR DSC7020, sample amount: about 30 mg, temperature rise rate: 15 ° C./min, and solid phase line. The temperature and the liquidus temperature were obtained. ΔT was obtained by subtracting the solidus temperature from the obtained liquidus temperature. When ΔT was 10 ° C. or lower, it was evaluated as “◯”, and when it exceeded 10 ° C., it was evaluated as “x”.

In Tables 8 and 9, Ag and Cu represent mass%, and Ni, Ge, As, Bi and Pb represent mass ppm.

As shown in Tables 8 and 9, all Example B showed stenosis of ΔT. In addition, it was found that all of Examples B showed excellent wettability.

[Combination of flux and solder alloy]
As a result of evaluating the solder paste containing the flux of Example A40 and the solder alloy of Example B1, good results were obtained in ΔT and wettability.

When various fluxes of Examples A41 to A56 were used instead of the flux of Example A40, good results were obtained in terms of ΔT and wettability.

Similarly, when the various fluxes of Examples A40 to A56 were combined with the various solder alloys of the other Examples B, good results were obtained in terms of ΔT and wettability.

Further, in particular, the solder joint using an alloy containing 25 ppm or more of As was suppressed in yellowing as compared with the one containing no As when subjected to the aging treatment at 100 to 200 ° C. in the air atmosphere.

Claims (10)

Flux containing chlorendate for soldering solder alloys. The flux according to claim 1, wherein the content of the chlorendate is more than 0% by mass and 5% by mass or less with respect to the entire flux. Claim 1 that the chlorendic acid ester is at least one selected from the group consisting of chlorendic acid monomethyl ester, chlorendic acid monoethyl ester, chlorendic acid monoisopropyl ester, chlorendic acid monoethylene glycol ester, and chlorendic acid dimethyl ester. Or the flux according to 2. The flux according to any one of claims 1 to 3, further comprising a solvent. The flux according to claim 4, wherein the solvent is 2-propanol. The flux according to any one of claims 1 to 5, wherein the soldering is flow soldering. A method for producing a bonded body, which comprises a step of soldering a solder alloy to the surface of a substrate treated with a flux containing the chlorendate according to any one of claims 1 to 6 to form a bonded body. The manufacturing method according to claim 7, wherein the soldering is flow soldering. A bonded body obtained by the production method according to claim 7 or 8. Flux activator containing chlorendate.