JP6681566B1 - Solder paste and flux - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solder paste and a flux which are excellent in corrosion inhibiting property of a metal surface, have a thickening inhibiting effect, are excellent in wettability, and have a small temperature difference between a liquidus temperature and a solidus temperature. SOLUTION: A flux containing an azole compound, an organic acid, and a solvent; and As: 25 to 300 mass ppm, Bi: 0 mass ppm or more and 25,000 mass ppm or less, Pb: 0 mass ppm or more and 8000 mass ppm or less, And the balance is Sn, and the following formulas (1) and (2): 275 ≦ 2As + Bi + Pb (1) 0 <2.3 × 10 −4 × Bi + 8.2 × 10 −4 × Pb ≦ 7 A solder paste containing (2) a solder alloy satisfying [in the formulas (1) and (2), As, Bi, and Pb each represent a content (mass ppm) in the alloy composition]. [Selection diagram] None

Description

  The present invention relates to a solder paste and flux used for soldering.

In recent years, in surface mounting of electronic components, reflow soldering has been performed in which solder that has been applied or bonded at room temperature in advance is heated and melted and then soldered.
In the case of reflow soldering using a solder paste, the solder paste is mainly composed of solder powder and a flux containing a resin component, a solvent and various additives, and this is applied to a planned joining portion by screen printing or the like and heated. By doing so, soldering is performed.

  As a solder paste used for such an application, for example, in Patent Document 1, an aromatic group and / or a fat is used as a cream solder having an appropriate fluidity and excellent printing characteristics without bleeding or sagging. Cream solders containing substituted urea compounds substituted with a group are described.

  Further, in recent years, as the size of the electrodes has been reduced, the printing area of the solder paste has also been narrowed, so that the time until the purchased solder paste is used up is prolonged. The solder paste is a mixture of solder powder and flux, and if the storage period is long, the viscosity of the solder paste will increase depending on the storage conditions and the printing performance at the time of purchase cannot be exhibited. Sometimes.

  Therefore, for example, Patent Document 2 includes Sn and one or more selected from the group consisting of Ag, Bi, Sb, Zn, In, and Cu in order to suppress the change over time of the solder paste. , And a solder alloy containing a predetermined amount of As is disclosed. The same document shows the result that the viscosity after 2 weeks at 25 ° C. is less than 140% as compared with the initial viscosity.

JP, 07-241695, A JP, 2005-98052, A

  The solder paste disclosed in Patent Document 1 may corrode a metal used for wiring such as copper after a lapse of a certain period after reflow soldering.

  Patent Document 2 shows the result that the meltability is poor when the As content is high, and the meltability is considered to correspond to the wettability of the molten solder. Generally, it is necessary to use a highly active flux in order to improve the wettability of the molten solder. In the flux described in Patent Document 2, it is considered that a highly active flux may be used in order to suppress deterioration of wettability due to As. However, if a highly active flux is used, the viscosity increase rate of the solder paste will increase. Further, in view of the description in Patent Document 2, it is necessary to increase the As content in order to suppress the increase in the viscosity increase rate. In order for the solder paste described in Patent Document 2 to exhibit a lower viscosity increase rate and excellent wettability, it is necessary to keep increasing the activity of the flux and the As content, which causes a vicious circle.

  Further, in order to bond fine electrodes, it is necessary to improve the mechanical characteristics and the like of the solder joint. Depending on the element, when the content increases, the liquidus temperature rises, the liquidus temperature and the solidus temperature widen, and segregates during solidification to form a non-uniform alloy structure. When the solder alloy has such an alloy structure, mechanical properties such as tensile strength are poor and the solder alloy easily breaks due to external stress. This problem has become more prominent with the recent miniaturization of electrodes.

  Therefore, the present invention provides a solder paste and a flux that have excellent corrosion inhibition of the metal surface, and also have an effect of inhibiting thickening, have excellent wettability, and have a small temperature difference between the liquidus temperature and the solidus temperature. The purpose is to provide.

  The present inventors have found that the use of a specific solder alloy exhibits an excellent effect of suppressing thickening, and further, that the flux contains an azole compound, the corrosion inhibiting property of the metal surface can be improved.

The present invention relates to the following [1] to [16].
[1]
A flux containing an azole compound, an organic acid, and a solvent; and As: 25 to 300 mass ppm, Bi: 0 mass ppm or more and 25,000 mass ppm or less, Pb: 0 mass ppm to 8000 mass ppm or less, and the balance Sn. The alloy composition has the following formulas (1) and (2):
275 ≦ 2As + Bi + Pb (1)
0 <2.3 × 10 ⁻⁴ × Bi + 8.2 × 10 ⁻⁴ × Pb ≦ 7 (2)
[In the above formulas (1) and (2), As, Bi and Pb each represent the content (mass ppm) in the alloy composition].
Satisfying solder alloy;
Including solder paste.
[2]
The azole compound is at least one selected from the group consisting of 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-heptadecylimidazole, benzimidazole and 2-octylbenzimidazole, in the above [1]. The listed solder paste.
[3]
The solder paste according to the above [1] or [2], wherein the flux contains the azole compound in an amount of 0.1% by mass or more and 10% by mass or less based on the total mass of the flux.
[4]
The said paste contains the said organic acid 0.5 mass% or more and 20 mass% or less with respect to the said flux total mass, The solder paste in any one of said [1]-[3].
[5]
The said solder paste in any one of said [1]-[4] which further contains rosin.
[6]
The solder paste according to the above [5], wherein the flux contains 30% by mass or more and 60% by mass or less of the rosin with respect to the total mass of the flux.
[7]
The said solder paste in any one of said [1]-[6] which further contains a thixotropic agent.
[8]
The solder paste according to the above [7], wherein the flux contains the thixotropic agent in an amount of 1.5% by mass or more and 10% by mass or less based on the total mass of the flux.
[9]
The solder paste according to any of [1] to [8] above, wherein the solder alloy has a particulate form.
[10]
The solder alloy has the following formula (1a):
275 ≦ 2As + Bi + Pb ≦ 25200 (1a)
[In the formula (1a), As, Bi, and Pb each represent the content (mass ppm) in the alloy composition]
The solder paste according to any one of [1] to [9], which satisfies the above condition.
[11]
The solder alloy has the following formula (1b):
275 ≦ 2As + Bi + Pb ≦ 5300 (1b)
[In the formula (1b), As, Bi, and Pb each represent the content (mass ppm) in the alloy composition]
The solder paste according to any one of the above [1] to [10], which satisfies the above condition.
[12]
The solder alloy has the following formula (2a):
0.02 ≦ 2.3 × 10 ⁻⁴ × Bi + 8.2 × 10 ⁻⁴ × Pb ≦ 0.9 (2a)
[In the above formula (2a), Bi and Pb each represent the content (mass ppm) in the alloy composition]
The solder paste according to any one of [1] to [11], which satisfies the above condition.
[13]
Further, the solder paste according to any one of the above [1], wherein the alloy composition contains at least one of Ag: 0 to 4 mass% and Cu: 0 to 0.9 mass%.
[14]
Furthermore, the solder paste according to any one of the above [1] to [13], which contains zirconium oxide powder.
[15]
The solder paste according to the above [14], which contains the zirconium oxide powder in an amount of 0.05 to 20.0 mass% with respect to the total mass of the solder paste.
[16]
As: 25-300 mass ppm, Bi: 0 mass ppm or more and 25,000 mass ppm or less, Pb: more than 0 mass ppm and 8,000 mass ppm or less, and the balance has an alloy composition of Sn, and the following formula (1) and (2) )formula:
275 ≦ 2As + Bi + Pb (1)
0 <2.3 × 10 ⁻⁴ × Bi + 8.2 × 10 ⁻⁴ × Pb ≦ 7 (2)
[In the above formulas (1) and (2), As, Bi and Pb each represent the content (mass ppm) in the alloy composition].
For soldering a solder alloy that satisfies the
A flux containing an azole compound, an organic acid, and a solvent.

  ADVANTAGE OF THE INVENTION According to this invention, it is excellent in corrosion inhibitory property of a metal surface, and also has a thickening inhibitory effect, is excellent in wettability, and has a small temperature difference between a liquidus temperature and a solidus temperature. Can be provided.

  Hereinafter, embodiments for carrying out the present invention (hereinafter, referred to as “the present embodiment”) will be described in more detail. However, the present invention is not limited to these, and various modifications may be made without departing from the gist thereof. Deformation is possible.

[Solder paste]
The solder paste of this embodiment contains a flux and a solder alloy.
The above-mentioned flux contains an azole compound, an organic acid, and a solvent.
The above-mentioned solder alloy has an alloy composition of As: 25 to 300 mass ppm, Bi: 0 mass ppm to 25,000 mass ppm, Pb: more than 0 mass ppm and 8,000 mass ppm, and the balance of Sn, and the following ( Formula 1 and formula (2):
275 ≦ 2As + Bi + Pb (1)
0 <2.3 × 10 ⁻⁴ × Bi + 8.2 × 10 ⁻⁴ × Pb ≦ 7 (2)
[In the above formulas (1) and (2), As, Bi and Pb each represent the content (mass ppm) in the alloy composition].
Meet.
According to the solder paste of the present embodiment, it has a thickening suppressing effect and excellent corrosion suppressing properties.

<Flux>
(Azole compound)
The flux of this embodiment contains an azole compound. By combining with an organic acid described below, it is possible to improve the corrosion inhibiting property of the metal surface (for example, copper plate) of the object to be joined.
The "azole compound" as used herein means a compound having a hetero 5-membered ring structure containing one or more nitrogen atoms, and also includes a condensed ring of the hetero 5-membered ring structure and another ring structure.

  Examples of the azole compound include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4. -Methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4 -Methylimidazole, 1-cyanoethyl-2-phenylimidazole, 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, epoxy-imidazole adduct, 2-methylbenzimidazole, 2-octylbenzimidazole, 2-pentylbenzimidazole, 2- (1-ethylpentyl) Benzimidazole, 2-nonylbenzimidazole, 2- (4-thiazolyl) benzimidazole, benzimidazole, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'- tert-Butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) benzotriazole, 2- (2'-hydroxy-5). '-Tert-octylphenyl) benzotriazole, 2, '-Methylenebis [6- (2H-benzotriazol-2-yl) -4-tert-octylphenol], 1,2,3-benzotriazole, 1- [N, N-bis (2-ethylhexyl) aminomethyl] benzo Triazole, carboxybenzotriazole, 1- [N, N-bis (2-ethylhexyl) aminomethyl] methylbenzotriazole, 2,2 '-[[(methyl-1H-benzotriazol-1-yl) methyl] imino] bis Ethanol, 1- (1 ', 2'-dicarboxyethyl) benzotriazole, 1- (2,3-dicarboxypropyl) benzotriazole, 1-[(2-ethylhexylamino) methyl] benzotriazole, 2,6- Bis [(1H-benzotriazol-1-yl) methyl] -4-methylphenol, 5-methylbenzotriazole, 5-phenyltetrazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 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, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazole Phosphorus, 6- (2-benzotriazolyl) -4-tert-octyl-6'-tert-butyl-4'-methyl-2,2'-methylene bisphenol, and the like.

The azole compounds may be used alone or in combination of two or more.
The azole compound is preferably at least one selected from the group consisting of 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-heptadecylimidazole, benzimidazole and 2-octylbenzimidazole, and 2-phenyl Those containing imidazole are more preferable.
The flux of the present embodiment preferably contains an azole compound in an amount of 0.1% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 5.0% by mass or less.

(Organic acid)
The flux of this embodiment contains an organic acid.
Organic acids include glutaric acid, adipic acid, azelaic acid, eicosane diacid, citric acid, glycolic acid, succinic acid, salicylic acid, diglycolic acid, dipicolinic acid, dibutylaniline diglycolic acid, suberic acid, sebacic acid, thioglycol. Acid, terephthalic acid, dodecanedioic acid, parahydroxyphenylacetic acid, picolinic acid, phenylsuccinic acid, phthalic acid, fumaric acid, maleic acid, malonic acid, lauric acid, benzoic acid, tartaric acid, isocyanuric acid tris (2-carboxyethyl) , Glycine, 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-quinolinecarboxylic acid, 3-hydroxybenzoic acid, Gore acid, p- anisic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, and linolenic acid.

  Examples of the organic acid include dimer acid, trimer acid, hydrogenated dimer acid which is a hydrogenated product of dimer acid, and hydrogenated trimer acid which is a hydrogenated product of trimer acid.

  For example, dimer acid which is a reaction product of oleic acid and linoleic acid, trimer acid which is a reaction product of oleic acid and linoleic acid, dimer acid which is a reaction product of acrylic acid, trimer acid which is a reaction product of acrylic acid, and methacrylic acid. The reaction product of dimer acid, the reaction product of methacrylic acid is trimer acid, the reaction product of acrylic acid and methacrylic acid is dimer acid, the reaction product of acrylic acid and methacrylic acid is trimer acid, and the reaction product of oleic acid. A dimer acid, a trimer acid that is a reaction product of oleic acid, a dimer acid that is a reaction product of linoleic acid, a trimer acid that is a reaction product of linoleic acid, a dimer acid that is a reaction product of linolenic acid, and a reaction product of linolenic acid. Some trimer acids, dimer acid which is a reaction product of acrylic acid and oleic acid, trimer acid which is a reaction product of acrylic acid and oleic acid, Dimer acid which is a reaction product of lylic acid and linoleic acid, trimer acid which is a reaction product of acrylic acid and linoleic acid, dimer acid which is a reaction product of acrylic acid and linolenic acid, and trimer which is a reaction product of acrylic acid and linolenic acid Acid, a reaction product of methacrylic acid and oleic acid, dimer acid, a reaction product of methacrylic acid and oleic acid, trimer acid, a reaction product of methacrylic acid and linoleic acid, a reaction product of methacrylic acid and linoleic acid. Some trimer acid, dimer acid which is the reaction product of methacrylic acid and linolenic acid, trimer acid which is the reaction product of methacrylic acid and linolenic acid, dimer acid which is the reaction product of oleic acid and linolenic acid, and reaction of oleic acid and linolenic acid Trimer acid which is a substance, dimer acid which is a reaction product of linoleic acid and linolenic acid, and a reaction product of linoleic acid and linolenic acid Trimer acid that, hydrogenated dimer acid which is a hydrogenation product of the dimer acid as described above, hydrogenated trimer acid, and the like are hydrogenated products of the trimer acid described above.

The organic acids may be used alone or in combination of two or more.
The flux of the present embodiment preferably contains 0.5% by mass or more and 20% by mass or less of an organic acid, more preferably 3% by mass or more and 18% by mass or less.

  In the flux of the present embodiment, the ratio of the content of the organic acid and the content of the azole compound is 0.5 or more and 10 or less as a mass ratio represented by the content of the organic acid / the content of the azole compound. Is preferable, and 1 or more and 9 or less is more preferable. If this mass ratio is within the above-mentioned preferable range, the corrosion inhibiting property of the metal surface (for example, copper plate) of the objects to be joined can be more easily enhanced.

  In the flux of the present embodiment, the total content of the organic acid and the azole compound is preferably 3% by mass or more, more preferably 5% by mass or more, and further preferably, based on the total mass of the flux. It is 6% by mass or more. The total content of the organic acid and the azole compound is preferably 30% by mass or less, more preferably 20% by mass or less, and further preferably 15% by mass or less, based on the total mass of the flux. . If this content is within the above-mentioned preferred range, the corrosion inhibiting property of the metal surface (for example, a copper plate) of the object to be bonded is likely to be enhanced, and the wettability tends to be further enhanced.

(Rosin)
The flux of this embodiment may contain rosin.
Examples of the rosin include raw rosins such as gum rosin, wood rosin and tall oil rosin, and derivatives obtained from the raw rosins. Examples of the derivative include purified rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, acid-modified rosin, phenol-modified rosin and α, β-unsaturated carboxylic acid modified products (acrylated rosin, maleated rosin, fumarized rosin. Rosin), and purified products of the polymerized rosin, hydrides and disproportionated products, and purified products of the α, β-unsaturated carboxylic acid modified products, hydrides and disproportionated products, and the like. Two or more can be used.

  The flux of the present embodiment preferably contains 30% by mass or more and 60% by mass or less of rosin, and more preferably contains 35% by mass or more and 60% by mass or less of rosin.

(Thixotropic agent)
Examples of thixotropic agents include wax thixotropic agents, amide thixotropic agents, and sorbitol thixotropic agents. Examples of the wax-based thixotropic agent include castor hydrogenated oil and the like. Examples of the amide thixotropic agent include a monoamide thixotropic agent, a bisamide thixotropic agent, and a polyamide thixotropic agent. Examples of the monoamide thixotropic agent include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, saturated fatty acid amide, oleic acid amide, erucic acid amide, unsaturated fatty acid amide, and p-toluamide. , P-toluenemethane amide, aromatic amide and the like. Examples of the bisamide thixotropic agent include methylenebisstearic acid amide, ethylenebislauric acid amide, ethylenebishydroxystearic acid amide, saturated fatty acid bisamide, methylenebisoleic acid amide, unsaturated fatty acid bisamide, and m-xylylenebisstearic acid. Amide, aromatic bisamide, etc. are mentioned. Examples of the polyamide-based thixotropic agent include saturated fatty acid polyamide, unsaturated fatty acid polyamide, aromatic polyamide, substituted amide, methylol stearic acid amide, methylol amide, and fatty acid ester amide. Examples of the sorbitol thixotropic agent include dibenzylidene-D-sorbitol and bis (4-methylbenzylidene) -D-sorbitol. The thixotropic agents may be used alone or in combination of two or more.

  The flux of the present embodiment is preferably 0.1 mass% or more and 15.0 mass% or less of the thixotropic agent, more preferably 1.0 mass% or more and 10.0 mass% or less of the thixotropic agent, and further preferably , Containing a thixotropic agent in an amount of 2.0% by mass to 8.3% by mass.

In addition, the flux of the present embodiment preferably contains an ester compound as a thixotropic agent, and the ester compound is contained in an amount of 0% by mass or more and 8.0% by mass or less, more preferably 0% by mass or more and 4.0% by mass. % Or less included.
Examples of the ester compound include castor hydrogenated oil and the like.

(Other additives)
The flux of the present embodiment may further contain amine (excluding azole compound) and halogen (organic halogen compound, amine hydrohalide). The flux of the present embodiment preferably contains 0% by mass or more and 20% by mass or less of amine (excluding azole compound), and more preferably contains 0% by mass or more and 5% by mass or less of amine. The flux of the present embodiment preferably contains an organic halogen compound as halogen in an amount of 0% by mass or more and 5% by mass or less, and preferably contains an amine hydrohalide salt in an amount of 0% by mass or more and 2% by mass or less.

  Examples of the amine include monoethanolamine, ethylamine, triethylamine, cyclohexylamine, ethylenediamine, triethylenetetramine, 2,4-diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid. Examples include adducts and 2,4-diamino-6-methacryloyloxyethyl-s-triazine.

  Examples of the organic halogen compound include trans-2,3-dibromo-2-butene-1,4-diol, triallyl isocyanurate hexabromide, 1-bromo-2-butanol, 1-bromo-2-propanol and 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, 2,3-dibromo-1,4-butanediol, 2,3-dibromo-2-butene-1,4-diol, tris (2,3-dibromopropyl) isocyanurate, Examples thereof include chlorendic anhydride.

The amine hydrohalide is a compound obtained by reacting an amine with hydrogen halide.
As the amine of the amine hydrohalide, the above-mentioned amines can be used, and examples thereof include ethylamine, cyclohexylamine, ethylenediamine, triethylamine, diphenylguanidine, ditolylguanidine, methylimidazole, 2-ethyl-4-methylimidazole and the like. To be Examples of hydrogen halides include hydrides of chlorine, bromine, iodine and fluorine (hydrogen chloride, hydrogen bromide, hydrogen iodide, hydrogen fluoride). Further, instead of the amine hydrohalide or in combination with the amine hydrohalide, borofluoride may be contained, and examples of the borofluoride include borofluoric acid.
Examples of the amine hydrohalide include aniline hydrogen chloride, cyclohexylamine hydrogen chloride, aniline hydrogen bromide, diphenylguanidine hydrogen bromide, ditolylguanidine hydrogen bromide, ethylamine hydrogen bromide and the like.

  The flux of the present embodiment may further contain an antioxidant, and examples of the antioxidant include a hindered phenol-based antioxidant and the like, and the antioxidant should be contained in an amount of 0% by mass or more and 5% by mass or less. Is preferred.

(solvent)
The flux of this embodiment contains a solvent.
Examples of the solvent include water, alcohol solvents, glycol ether solvents, terpineols and the like. Examples of alcohol solvents include isopropyl alcohol, 1,2-butanediol, isobornylcyclohexanol, 2,4-diethyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, and 2,5. -Dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyne-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, threitol, guaiacol glycerol ether, 3,6-dimethyl-4-octyne-3,6-diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol and the like can be mentioned. Examples of the glycol ether solvent include hexyl diglycol, 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. , Tetraethylene glycol monomethyl ether and the like.

  The balance of the flux of the present embodiment is a solvent, preferably 10.0% by mass or more and 90.0% by mass or less of the solvent, more preferably 20.0% by mass or more and 80.0% by mass or less of the solvent. More preferably, the solvent content is 30.0% or more and 70.0% by mass or less.

<Solder alloy>
The solder alloy has an alloy composition of As: 25 to 300 mass ppm, Bi: 0 mass ppm to 25000 mass ppm, Pb: 0 mass ppm to 8000 mass ppm, and the balance being Sn, and the following (1) Formula and Formula (2):
275 ≦ 2As + Bi + Pb (1)
0 <2.3 × 10 ⁻⁴ × Bi + 8.2 × 10 ⁻⁴ × Pb ≦ 7 (2)
[In the formulas (1) and (2), As, Bi, and Pb each represent the content (mass ppm) in the alloy composition].
The solder paste of the present embodiment can improve the thickening suppression effect by including the above solder alloy. Also, the solder alloy is provided with the configuration described above, it is possible to reduce the difference (ΔT = T _L -T _S) and the liquidus temperature (T _L) and the solidus temperature (T _S). Therefore, for example, even if the solder paste containing the solder alloy is applied to the substrate of the electronic device and solidified, the solder paste can maintain the uniformity of the structure of the solder alloy. As a result, the solder paste has excellent reliability such as cycle characteristics. Further, since the solder alloy constituting the solder paste of the present embodiment is excellent in wettability by having the above-mentioned constitution, it is possible to suppress the occurrence of defective soldering. As described above, the solder paste having the above-described configuration has a thickening suppressing effect, is excellent in wettability, and has a small temperature difference between the liquidus temperature and the solidus temperature.

  As is an element that can suppress the change in viscosity of the solder paste with time. Since As has a low reactivity with flux and is a noble element with respect to Sn, it is presumed that it can exert a thickening suppressing effect. 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 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 are elements having low reactivity with flux and exhibiting a thickening suppressing effect. Further, these elements are elements that can suppress the deterioration of the wettability due to As, since they lower the liquidus temperature of the solder alloy and the viscosity of the molten solder.

  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 Bi content is more than 0 mass ppm, preferably 25 mass ppm or more, more preferably 50 mass ppm or more, and further preferably 75 mass ppm or more. It is at least ppm by mass, particularly preferably at least 100 ppm by mass, and most preferably at least 250 ppm by mass. When the solder alloy according to the present embodiment contains Pb, the lower limit of the Pb content is more than 0 mass ppm, preferably 25 mass ppm or more, more preferably 50 mass ppm or more, and further preferably 75 mass ppm or more. It is at least ppm by mass, particularly preferably at least 100 ppm by mass, and most preferably at least 250 ppm by mass.

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

From such a viewpoint, 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 1,000 mass ppm or less. Yes, more preferably 600 mass ppm or less, and particularly preferably 500 mass ppm or less. If the solder alloy according to the present embodiment contains Pb, Kirichi on the Pb content is not more than 8000 mass ppm, preferably not more than 5100 mass ppm, more preferably not more than 5000 mass ppm, more preferably 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 satisfies the following formula (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.

  Each of As, Bi and Pb is an element having a thickening suppressing effect. The total of these is 230 mass ppm or more. In the formula (1), the reason why the As content is doubled is that As has a higher effect of suppressing thickening than Bi or Pb.

  When the formula (1) is less than 275, the thickening suppressing effect is not sufficiently exhibited. The lower limit of the formula (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 effect of suppressing thickening, but is preferably 25200 or less, and 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 formulas (1a) and (1b) are obtained by appropriately selecting the upper limit and the lower limit from the above-described 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 satisfies the following formula (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 deterioration of wettability due to the inclusion of As, but if the contents are too large, ΔT increases, so strict control is required. Particularly, in the 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 the 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 ΔT significantly increases even if the content is slightly increased.

  The solder alloy in which the formula (2) is 0 does not contain both elements of Bi and Pb, and thus the deterioration of the wettability due to the inclusion of As cannot be suppressed. The lower limit of the formula (2) is more than 0, preferably 0.02 or more, more preferably 0.03 or more, still more preferably 0.05 or more, and particularly preferably 0.06 or more. , And most preferably 0.11 or more. On the other hand, when the expression (2) exceeds 7, the temperature range of ΔT becomes too wide, so that the crystal phase having a high concentration of Bi and Pb is segregated during solidification of the molten solder to deteriorate mechanical strength and the like. 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 still more preferably 4.18 or less. , Particularly preferably 2.30 or less, and most preferably 0.90 or less.

  The formula (2a) below is obtained by appropriately selecting the upper limit and the lower limit from the above-mentioned preferred embodiments.

0.02 ≦ 2.3 × 10 ⁻⁴ × Bi + 8.2 × 10 ⁻⁴ × 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 optional element that can form Ag ₃ Sn at the crystal interface to improve the mechanical strength and the like of the solder alloy. Further, Ag is an element having an ionization tendency that is noble with respect to Sn, and coexists with As, Pb, and Bi to promote these thickening suppressing effects. The Ag content is preferably 0 to 4%, more preferably 0.5 to 3.5%, still more preferably 1.0 to 3.0%.

  Cu is an arbitrary element that can improve the bonding strength of the solder joint. Further, Cu is an element having an ionization tendency that is noble with respect to Sn, and coexists with As, Pb, and Bi to promote these thickening suppressing effects. The Cu content is preferably 0 to 0.9%, more preferably 0.1 to 0.8%, and further preferably 0.2 to 0.7%.

  The balance 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 inevitable impurities, it does not affect the above-mentioned effects. Further, as will be described later, even if an element which is 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, it does not affect the above-mentioned effect.

<Content of each component>
The contents of the solder alloy and the flux in the solder paste are not limited, and for example, the solder alloy can be 5 to 95 mass% and the flux can be 5 to 95 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 with the lapse of time. It is presumed that this is because the inclusion of zirconium oxide maintains the oxide film thickness on the surface of the solder powder in the state before being put into the flux. The details are unknown, but it is presumed to be as follows. Usually, the active component of the flux is slightly active even at room temperature, so that the surface oxide film of the solder powder becomes thin due to reduction, which causes the powder particles to aggregate. Therefore, it is presumed that by adding zirconium oxide powder to the solder paste, the active component of the flux preferentially reacts with the zirconium oxide powder, and the oxide film on the surface of the solder powder is maintained so as not to aggregate.

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

  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. The particle size was determined by taking an SEM photograph of zirconium oxide powder, determining the projected circle equivalent diameter by image analysis for each powder of 0.1 μm or more, and taking the average value.

  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 the effect of suppressing viscosity increase is obtained. When it is spherical, good flowability is obtained, and thus excellent printability as a paste is obtained. The shape may be appropriately selected according to desired characteristics.

The method for manufacturing the solder paste of the present embodiment is not limited, and the solder paste can be manufactured by mixing the raw materials simultaneously or sequentially by an arbitrary method.
In manufacturing the flux, all the components of the flux may be finally mixed, and various kinds may be mixed in advance as a mixed solvent, or may be mixed with various components at different timings.
Further, also in the production of the solder paste, it is not always necessary to prepare the flux in advance and mix it with the solder alloy, and finally all the components of the flux, the solder alloy and, if necessary, added to the solder paste. If the additives are mixed with each other, the order of mixing is not limited, and after mixing a part of the components of the flux and the solder alloy, the remaining components of the flux may be added.

  The solder paste according to the present embodiment can exhibit a high corrosion inhibition property with respect to the metal surface (for example, a copper plate) of the object to be joined.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[Examination of flux]
The raw materials shown in Table 1 were mixed in the composition shown in Table 1 to prepare the fluxes of Examples A1 to A61 and Comparative Example A1. The raw materials were compatible with each other and could be easily mixed.

  With respect to the fluxes of Examples and Comparative Examples, the copper plate corrosion inhibition ability was evaluated by the following procedure.

<Evaluation of corrosion inhibition ability>
(1) Verification method The corrosion inhibition ability was evaluated by the following copper plate corrosion test according to JIS Z 3197: 2012 8.4.1.

  Preparation of test copper plate: A test piece was prepared by making a recess having a depth of 3 mm with a steel ball having a diameter of 20 mm at the center of a phosphor deoxidized copper plate having dimensions of 50 mm x 50 mm x 0.5 mm. The test piece was degreased with acetone and then immersed in sulfuric acid at 65 ° C. for 1 minute to remove the oxide film on the surface. Next, after being immersed in an ammonium persulfate solution at 20 ° C. for 1 minute, it was washed with purified water and dried to obtain a test copper plate.

The solid content of the flux of each example was measured by the method specified in JIS Z 3197: 2012 8.1.3, and an appropriate amount of flux containing 0.035 to 0.040 g as the solid content was measured. The test copper plate was added to the hollow in the center.
Next, the test copper plate was put into a constant temperature and constant humidity chamber set to a humidity condition of a temperature of 40 ° C. and a relative humidity of 90%, and left in the chamber for 72 hours. There were two test copper plates for each flux of each example, and one blank was added.
After leaving it in the bath for 96 hours, it was taken out from the thermo-hygrostat and the trace of corrosion was compared with that of the blank under a microscope of 30 times. The corrosion inhibition ability was evaluated based on the criteria shown below.

(2) Criteria ○: No discoloration ×: Discoloration

  Table 1 shows the results. The fluxes of Examples A1 to A61 in which the flux contains an azole compound and an organic acid show better corrosion resistance than Comparative Example A1.

[Consideration of solder alloy]
A flux (A1) prepared in Table 1 and a solder alloy having a size (particle size distribution) satisfying the symbol 4 in the powder size classification (Table 2) according to JIS Z 3284-1: 2014, which is composed of the alloy compositions shown in Tables 2 to 7. Were mixed to prepare a solder paste. The mass ratio of the flux to the solder alloy is flux: solder alloy = 11: 89. For each solder paste, the change in viscosity with time was measured. Further, the liquidus temperature and solidus temperature of the solder alloy were measured. Furthermore, the wettability was evaluated using the solder paste immediately after production. Details are as follows.

<Suppression of thickening>
For each solder paste immediately after production, the viscosity was measured for 12 hours in the atmosphere at 25 rpm and 25 rpm using Malcolm's PCU-205. If the viscosity after 12 hours is 1.2 times or less as compared with the viscosity after 30 minutes have passed after making the solder paste, it was evaluated as "○" as having a sufficient thickening suppressing effect, When it exceeded 1.2 times, it was evaluated as "x".

<Temperature difference between liquidus temperature and solidus temperature (ΔT)>
As for the solder alloy before mixing with the flux, DSC measurement was performed using SII Nano Technology Co., Ltd., model number: EXSTAR DSC7020, sample amount: about 30 mg, heating rate: 15 ° C./min, and solidus line The temperature and liquidus temperature were obtained. ΔT was calculated by subtracting the solidus temperature from the obtained liquidus temperature. When ΔT was 10 ° C. or less, it was evaluated as “◯”, and when it exceeded 10 ° C., it was evaluated as “x”.

<Wettability>
Immediately after production, each solder paste was printed on a Cu plate, heated from 25 ° C. to 260 ° C. at a temperature rising rate of 1 ° C./s in a N ₂ atmosphere in a reflow furnace, and then cooled to room temperature. The wettability was evaluated by observing the appearance of the solder bump 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”.

<Comprehensive evaluation>
◯: All of the above evaluations are ◯ ×: There is × in each of the above evaluations

With the solder paste using the flux of each of the examples shown in Table 1 and a predetermined solder alloy, an excellent effect on the corrosion inhibition ability of the solder paste was obtained.
The solder pastes using the predetermined flux shown in Table 2 and the solder alloys of various examples have a thickening suppressing effect, and have a small temperature difference (ΔT) between the liquidus temperature and the solidus temperature, Excellent wettability.

  As shown in Tables 2 to 7, it was found that all of Example B exhibited a thickening suppressing effect, a ΔT constriction, and excellent wettability.

  On the other hand, Comparative Examples B1, B10, B19, B28, B37, and B46 did not contain As, and therefore the thickening suppressing effect was not exhibited.

  In Comparative Examples B2, B11, B20, B29, B38, and B47, since the formula (1) was less than the lower limit, the thickening suppressing effect was not exhibited.

  Comparative Examples B3, B4, B12, B13, B21, B22, B30, B31, B39, B40, B48, and B49 exhibited poor wettability because the As content exceeded the upper limit.

  In Comparative Examples B5, B7, B9, B14, B16, B18, B23, B25, B27, B32, B34, B36, B41, B43, B45, B50, B52, and B54, the Pb content and the formula (2) are the upper limits. Since the value exceeds the value, the result shows that ΔT exceeds 10 ° C.

  Comparative Examples B6, B15, B24, B33, B42, and B51 showed the result that ΔT exceeded 10 ° C. because the formula (2) exceeded the upper limit.

  Comparative Examples B8, B17, B26, B35, B44, and B53 showed results in which ΔT exceeded 10 ° C. because the Bi content and the formula (2) exceeded the upper limits.

<Combination of flux and solder alloy>
Also in the case of combining the fluxes of Examples A2 to A61 instead of the flux of Example A1 with the solder alloys shown in Example B1, good corrosion inhibition, thickening inhibition effect, ΔT, and wettability were obtained. The results were obtained.

  Similarly, when various fluxes of Examples A1 to A61 are combined with various solder alloys of Example B, respectively, good results can be obtained with respect to corrosion inhibition, thickening inhibition, ΔT, and wettability. Was obtained.

<Addition of zirconium oxide powder to solder paste>
0.5% of the zirconium oxide powder having a particle diameter of 1 μm was added to the solder paste composed of the flux shown in Table 1 and the powder of each solder alloy shown in Tables 2 to 7 with respect to the total mass of the solder paste. When added, a better result was obtained regarding the effect of suppressing thickening. In addition, good results were obtained without deteriorating the corrosion inhibition effect, ΔT, and wettability.

  According to the present invention, it is possible to provide a solder paste and a flux that have excellent corrosion inhibition of the metal surface, and also have an effect of inhibiting thickening, have excellent wettability, and have a small temperature difference between the liquidus temperature and the solidus temperature. Can be provided.

Claims (14)

A flux containing an azole compound, an organic acid, and a solvent; and As: 25 to 300 mass ppm, Bi: 0 mass ppm or more and 25,000 mass ppm or less, Pb: 0 mass ppm to 8000 mass ppm or less, and the balance Sn. The alloy composition has the following formulas (1) and (2):
275 ≦ 2As + Bi + Pb (1)
0 <2.3 × 10 ⁻⁴ × Bi + 8.2 × 10 ⁻⁴ × Pb ≦ 7 (2)
[In the above formulas (1) and (2), As, Bi and Pb each represent the content (mass ppm) in the alloy composition].
Satisfying solder alloy;
Consists of
The azole compound is contained in an amount of 0.1% by mass or more and 10% by mass or less based on the total mass of the flux ,
The solder paste in which the total content of the organic acid and the azole compound is 10.1% by mass or more based on the total mass of the flux. A flux containing an azole compound, an organic acid, and a solvent; and As: 25 to 300 mass ppm, Bi: 0 mass ppm or more and 25,000 mass ppm or less, Pb: 0 mass ppm to 8000 mass ppm or less, and the balance Sn. The alloy composition has the following formulas (1) and (2):
275 ≦ 2As + Bi + Pb (1)
0 <2.3 × 10 ⁻⁴ × Bi + 8.2 × 10 ⁻⁴ × Pb ≦ 7 (2)
[In the above formulas (1) and (2), As, Bi and Pb each represent the content (mass ppm) in the alloy composition].
Satisfying solder alloy;
Consists of
2 mass% or more and 10 mass% or less of the azole compound with respect to the total mass of the flux ,
Solder paste in which the total content of the organic acid and the azole compound is 5% by mass or more based on the total mass of the flux.   The azole compound is at least one selected from the group consisting of 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-heptadecylimidazole, benzimidazole and 2-octylbenzimidazole. Solder paste described in.   The solder paste according to any one of claims 1 to 3, wherein the flux contains the azole compound in an amount of 0.1% by mass or more and 10% by mass or less based on the total mass of the flux.   The solder paste according to any one of claims 1 to 4, wherein the flux contains the organic acid in an amount of 0.5% by mass or more and 20% by mass or less with respect to the total mass of the flux.   The solder paste according to claim 1, wherein the flux further contains rosin.   The solder paste according to claim 6, wherein the flux contains 30 mass% or more and 60 mass% or less of the rosin with respect to the total mass of the flux.   The solder paste according to any one of claims 1 to 7, wherein the flux further contains a thixotropic agent.   The solder paste according to claim 8, wherein the flux contains the thixotropic agent in an amount of 1.5% by mass or more and 10% by mass or less based on the total mass of the flux.   The solder paste according to any one of claims 1 to 9, wherein the solder alloy has a particulate form. The solder alloy has the following formula (1a):
275 ≦ 2As + Bi + Pb ≦ 25200 (1a)
[In the formula (1a), As, Bi, and Pb each represent the content (mass ppm) in the alloy composition]
The solder paste according to claim 1, which satisfies the above condition. The solder alloy has the following formula (1b):
275 ≦ 2As + Bi + Pb ≦ 5300 (1b)
[In the formula (1b), As, Bi, and Pb each represent the content (mass ppm) in the alloy composition]
The solder paste according to any one of claims 1 to 11, which satisfies the above condition. The solder alloy has the following formula (2a):
0.02 ≦ 2.3 × 10 ⁻⁴ × Bi + 8.2 × 10 ⁻⁴ × Pb ≦ 0.9 (2a)
[In the above formula (2a), Bi and Pb each represent the content (mass ppm) in the alloy composition]
The solder paste according to any one of claims 1 to 12, which satisfies the above condition.   Furthermore, the said alloy composition contains Ag: 0-4 mass% and Cu: 0-0.9 mass% at least 1 sort (s), The solder paste as described in any one of Claims 1-13.