JP6676244B1 - Flux and solder paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solder paste having an excellent thickening suppressing effect. A flux containing a compound represented by the following general formula (1), a rosin, and a solvent, As: 25 to 300 mass ppm, Bi: 0 to 25,000 mass ppm, Pb: more than 0 to 8000. The alloy composition has mass ppm 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 Solder paste containing a solder alloy satisfying × Pb ≦ 7 (2) [in the formulas (1) and (2), As, Bi, and Pb each represent the content in the alloy composition]. [Selection diagram] None

Description

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

  The solder composition (solder paste) is a mixture obtained by kneading a flux composition (a rosin-based resin, an activator, a solvent, and the like) with a solder powder to form a paste. The solder composition is required to have solder melting property and a property that solder is easily spread and spread (solder spread and spread), as well as suppression of solder balls generated between pads (lands) after reflow and printability. Among these required characteristics, a particularly high printability (viscosity stability at the time of continuous printing and other various characteristics) may be required from the viewpoint of productivity of a mounting board or the like. Further, from the viewpoint of miniaturization of the mounting board, more reliable suppression of solder balls may be required at the same time. In order to solve these problems, studies have been made on an activator and the like in a flux composition (for example, Patent Document 1).

JP 2006-110580 A

  However, the solder paste described in Patent Document 1 is not yet sufficient from the viewpoint of suppressing thickening.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a solder paste having an excellent effect of suppressing thickening.

  The present inventors have conducted intensive studies in order to solve the above-described problems, and as a result, have increased the use of a solder paste combining a flux containing a specific activator represented by the general formula (1) and a solder alloy having a specific composition. It has been found that the viscosity suppressing effect can be improved.

That is, the present invention is as follows.
[1]
A flux containing a compound represented by the following general formula (1), rosin, and a solvent,
As: 25 to 300 mass ppm, Bi: 0 mass ppm or more to 25,000 mass ppm, Pb: more than 0 mass ppm to 8000 mass ppm, and the balance has an alloy composition consisting 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]
A solder alloy that satisfies
Including, solder paste.

[In the formula (1), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ]
[2]
The solder paste according to [1], wherein the compound represented by the general formula (1) is picolinic acid.
[3]
The solder paste according to [1] or [2], wherein the flux further includes a thixotropic agent.
[4]
The solder paste according to any of [1] to [3], wherein the flux contains the compound represented by the general formula (1) in an amount of 0.5 wt% to 7.0 wt%.
[5]
The solder paste according to any one of [1] to [4], wherein the flux contains the rosin in an amount of 30 wt% to 60 wt%.
[6]
The solder paste according to any of [3] to [5], wherein the flux contains the thixotropic agent in a total amount of 0 wt% to 15 wt%.
[7]
The flux further comprises:
Amine in a range of 0 wt% to 20 wt%,
0% to 5% by weight of an organic halogen compound;
The solder paste according to any one of [1] to [6], wherein the solder paste contains 0% to 2% by weight of an amine hydrohalide or 0% to 5% by weight of an antioxidant.
[8]
The flux further includes an organic acid,
The solder paste according to any of [1] to [7], wherein the total amount of the compound represented by the general formula (1) and the organic acid is 3 wt% or more.
[9]
As: 25 to 300 mass ppm, Bi: 0 mass ppm or more to 25,000 mass ppm, Pb: more than 0 mass ppm to 8000 mass ppm, and the balance has an alloy composition consisting 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]
Flux for soldering a solder alloy that satisfies
A flux containing a compound represented by the following general formula (1), rosin, and a solvent.

[In the formula (1), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ]

  In the solder paste of the present invention, by combining a flux containing the compound represented by the general formula (1) as a specific activator with a solder alloy having a specific composition, the effect of suppressing thickening can be enhanced.

<Example of flux of the present embodiment>
The flux of the present embodiment contains a compound represented by the general formula (1), rosin, and a solvent.

The flux of the present embodiment may contain a thixotropic agent.
Examples of the thixo agent include a wax thixo agent, an amide thixo agent, and a sorbitol thixo agent. Examples of the wax-based thixotropic agent include castor hardened oil. Amide-based thixotropic agents include monoamide-based thixotropic agents, bisamide-based thixotropic agents, and polyamide-based thixotropic agents.Specifically, 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, p-toluene methane amide, aromatic amide, methylene bisstearic acid amide, ethylene bislauric amide, ethylene bishydroxystearic acid amide, saturated fatty acid bis amide , Methylene bisoleic acid amide, unsaturated fatty acid bisamide, m-xylylene bisstearic acid amide, aromatic bisamide, saturated fatty acid polyamide, unsaturated fatty acid polyamide, aromatic Polyamide, substituted amide, methylol stearic acid amide, methylol amide, fatty acid ester amide, and the like. Examples of the sorbitol thixotropic agent include dibenzylidene-D-sorbitol, bis (4-methylbenzylidene) -D-sorbitol, and the like.

  Further, the flux of the present embodiment may contain an ester compound as a thixotropic agent. Examples of the ester compound include castor hardened oil.

  The total amount of the thixotropic agent contained in the flux is preferably from 0 wt% to 15 wt%, more preferably from 0 wt% to 10 wt%. Further, the content of the amide-based thixotropic agent is preferably from 0 wt% to 12 wt%, and the content of the ester compound is preferably from 0 wt% to 8.0 wt%, more preferably from 0 wt% to 4.0 wt%. is there.

<Specific activator>
The flux of the present embodiment contains a compound represented by the following general formula (1) as a specific activator.

［式（１）中、Ｒ¹、Ｒ²、Ｒ³及びＲ⁴は、それぞれ独立に、水素原子または炭素数１〜４のアルキル基を示す。］

[In the formula (1), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ]

In Formula ^{(1), R 1, R} 2, R 3 and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, a propyl group, a cyclopropyl group, a butyl group, and a cyclobutyl group. Among them, R ¹ , R ² , R ³ and R ⁴ are preferably a hydrogen atom, a methyl group, an ethyl group or a cyclopropyl group, more preferably a hydrogen atom or a methyl group, and more preferably a hydrogen atom. Is particularly preferred. R ¹ , R ² , R ³ and R ⁴ may be the same or different.

Examples of the compound represented by the general formula (1) include picolinic acid, 6-methylpicolinic acid, 6-ethylpicolinic acid, 3-cyclopropylpicolinic acid, 4-cyclopropylpicolinic acid, 6-cyclopropylpicolinic acid, 5-butylpicolinic acid, 6-cyclobutylpicolinic acid and the like. Among these, picolinic acid is particularly preferred.
As the compound represented by the general formula (1), one type may be used alone, or two or more types may be used in combination.

  The flux of the present embodiment preferably contains the compound represented by the general formula (1) in an amount of 0.5 wt% or more and 7 wt% or less, more preferably 1.0 wt% of the compound represented by the general formula (1). % Or more and 5.0 wt% or less.

  Examples of the rosin include raw rosins such as gum rosin, wood rosin and tall oil rosin, and derivatives obtained from the raw rosin. 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, fumaric rosin, Rosin, etc.), and purified, hydrogenated and disproportionated products of the polymerized rosin, and purified, hydrided and disproportionated products of the α, β unsaturated carboxylic acid-modified product. Two or more can be used.

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

  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, 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] ate 1,1-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. Examples of glycol ether solvents 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, and triethylene glycol monobutyl ether. And tetraethylene glycol monomethyl ether.

  The flux of the present embodiment may further contain an organic acid (excluding the compound represented by the general formula (1)), an amine, and a halogen (organic halogen compound, amine hydrohalide). The flux of the present embodiment preferably contains an organic acid in a range of 0 wt% to 10 wt%. The flux of the present embodiment preferably contains the amine in an amount of 0 wt% or more and 20 wt% or less, and more preferably the amine contains 0 wt% or more and 5 wt% or less. The flux of the present embodiment preferably contains an organic halogen compound as halogen in an amount of 0 wt% to 5 wt%, and preferably contains an amine hydrohalide salt in an amount of 0 wt% to 2 wt%.

  Further, the total amount of the compound represented by the general formula (1) and the organic acid is preferably at least 3 wt%, more preferably at least 6.5 wt%.

  Examples of the organic acids (excluding the compound represented by the general formula (1)) 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, thioglycolic acid, terephthalic acid, dodecandioic acid, parahydroxyphenylacetic acid, phenylsuccinic acid, phthalic acid, fumaric acid, maleic acid, malonic acid, lauric acid, benzoic acid, Tartaric acid, tris (2-carboxyethyl) isocyanurate, 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, - hydroxybenzoic acid, malic 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 obtained by adding hydrogen to dimer acid, and hydrogenated trimer acid which is a hydrogenated product obtained by adding hydrogen to 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 Dimer acid, which is a reactant of methacrylic acid, dimer acid which is a reactant of acrylic acid and methacrylic acid, trimer acid which is a reactant of acrylic acid and methacrylic acid, and a reactant of oleic acid Certain dimer acids, trimer acid which is a reaction product of oleic acid, dimer acid which is a reaction product of linoleic acid, trimer acid which is a reaction product of linoleic acid, dimer acid which is a reaction product of linolenic acid, and a reaction product of linolenic acid Certain 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 a trimer which is a reaction product of acrylic acid and linolenic acid Acid, dimer acid which is a reaction product of methacrylic acid and oleic acid, trimer acid which is a reaction product of methacrylic acid and oleic acid, dimer acid which is a reaction product of methacrylic acid and linoleic acid, a reaction product of methacrylic acid and linoleic acid Certain trimer acid, dimer acid which is a reaction product of methacrylic acid and linolenic acid, trimer acid which is a reaction product of methacrylic acid and linolenic acid, dimer acid which is a reaction product of oleic acid and linolenic acid, reaction of oleic acid and linolenic acid Dimer acid, 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.

  Examples of the amine include monoethanolamine, diphenylguanidine, ditolylguanidine, ethylamine, triethylamine, cyclohexylamine, ethylenediamine, triethylenetetramine, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, and 1,2-dimethyl. Imidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methyl Imidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 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, 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, 2,4-diamino-6-vinyl-s- Triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyl-s-triazine, epoxy-imidazole adduct, 2-methylbenzimidazole, 2-octyl Benzimidazole, 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, 2,2′-methylenebis [6- (2H-benzotriazol-2-yl) -4-tert-octylphenol], 6 -(2-benzotriazolyl) -4-tert-octyl-6'-tert-butyl-4'-methyl-2,2'-methylenebisphenol, 1,2,3-benzotriazole, 1- [N, N-bis (2-ethylhexyl) aminomethyl] benzotriazole, carboxybenzotriazole, 1- [N, N-bis (2-ethyl Xyl) aminomethyl] methylbenzotriazole, 2,2 ′-[[(methyl-1H-benzotriazol-1-yl) methyl] imino] bisethanol, 1- (1 ′, 2′-dicarboxyethyl) benzotriazole , 1- (2,3-dicarboxypropyl) benzotriazole, 1-[(2-ethylhexylamino) methyl] benzotriazole, 2,6-bis [(1H-benzotriazol-1-yl) methyl] -4- Examples include methylphenol, 5-methylbenzotriazole, 5-phenyltetrazole and the like.

  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, 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, Chlorendic anhydride and the like can be mentioned.

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, and 2-ethyl-4-methylimidazole. Can be Examples of the hydrogen halide include hydrides of chlorine, bromine, iodine, and fluorine (hydrogen chloride, hydrogen bromide, hydrogen iodide, hydrogen fluoride). Further, a borofluoride may be contained in place of the amine hydrohalide or in combination with the amine hydrohalide, 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, and ethylamine hydrogen bromide.

  The flux of the present embodiment may further contain an antioxidant, and examples of the antioxidant include a hindered phenol-based antioxidant, and the antioxidant preferably contains 0 wt% or more and 5 wt% or less. . The balance of the flux of the present embodiment is a solvent.

<Solder alloy>
The solder alloy of the present embodiment is
As: 25 to 300 mass ppm, Bi: 0 mass ppm or more to 25,000 mass ppm, Pb: more than 0 mass ppm to 8000 mass ppm, and the balance has an alloy composition consisting 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]
Meet.

  As is an element capable of suppressing a change with time in the viscosity of the solder paste. It is presumed that As has low reactivity with flux and is an element noble to Sn, so that it can exhibit a thickening suppressing effect. When As is less than 25 ppm by mass, the effect of suppressing thickening cannot be sufficiently exhibited. The lower limit of the As content is 25 ppm by mass or more, preferably 50 ppm by mass or more, and more preferably 100 ppm by mass or more. On the other hand, if the content of As is too large, the wettability of the solder alloy deteriorates. The upper limit of the As content is 300 ppm by mass or less, preferably 250 ppm by mass or less, and more preferably 200 ppm by mass or less.

  Bi and Pb are elements having low reactivity with the flux and exhibiting a thickening suppressing effect. Further, these elements are elements that can suppress the deterioration of wettability due to As by lowering the liquidus temperature of the solder alloy.

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

  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, a liquid phase Bi or Pb is concentrated in the solidification process of the molten solder because a high melting point crystalline phase having a low content of Bi or Pb is deposited. Thereafter, when the temperature of the molten solder further decreases, a low melting point crystalline phase having a high concentration of Bi or Pb segregates. For this reason, the mechanical strength and the like of the solder alloy deteriorate. In particular, since the crystal phase having a high Bi concentration is hard and brittle, segregation in the solder alloy significantly lowers the mechanical strength and the like.

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 10000 mass ppm or less, more preferably 1000 mass ppm or less. And more preferably at most 600 ppm by mass, particularly preferably at most 500 ppm by mass. 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 ppm by mass or less, particularly preferably 850 ppm by mass or less, and most preferably 500 ppm by mass or less.

  The solder alloy according to the present embodiment needs to satisfy the following expression (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 exhibit a thickening suppressing effect. It is preferable that the sum of these needs to be 230 mass ppm or more. In the formula (1), the reason why the As content is doubled is that As has a higher viscosity-suppressing effect than Bi or Pb.

  If the value of the expression (1) is less than 275, the effect of suppressing thickening 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 even more 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, more preferably 15200 or less, from the viewpoint of setting ΔT in a suitable range. It is more preferably at most 10,200, particularly preferably at most 8,200, most preferably at most 5,300.

  The following formulas (1a) and (1b) are those in which the upper and lower limits are appropriately selected 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 the present embodiment needs to satisfy the following expression (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. However, if the content is too large, ΔT increases, so strict control is required. In particular, in an alloy composition containing Bi and Pb simultaneously, ΔT tends to increase. In the present embodiment, the increase in ΔT can be suppressed by defining the sum of the values obtained by multiplying the Bi and Pb contents 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 large contribution to ΔT as compared with Bi, and ΔT greatly increases even if the content is slightly increased.

  (2) Since the solder alloy having the formula 0 does not contain both elements of Bi and Pb, deterioration of wettability due to containing 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, further more preferably 0.05 or more, and particularly preferably 0.06 or more. , Most preferably 0.11 or more. On the other hand, if the expression (2) exceeds 7, the temperature range of ΔT becomes too wide, so that a crystal phase having a high concentration of Bi or 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, still more preferably 5.75 or less, and even more preferably 4.18 or less. , Particularly preferably 2.30 or less, and most preferably 0.90 or less.

  The following formula (2a) is obtained by appropriately selecting the upper and lower limits from the above 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. Ag is an element having a higher ionization tendency than Sn and coexists with As, Pb, and Bi to promote the effect of suppressing thickening. Ag content is preferably 0 to 4%, more preferably 0.5 to 3.5%, and still more preferably 1.0 to 3.0%.

  Cu is an optional element that can improve the bonding strength of the solder joint. Further, Cu is an element having a higher ionization tendency than Sn and coexists with As, Pb and Bi to promote 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 still more preferably 0.2 to 0.7%.

  The balance of the solder alloy according to the present embodiment is Sn. Inevitable impurities may be contained in addition to the aforementioned elements. Even if unavoidable impurities are contained, the effects described above are not affected. Further, as 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 is widened. Therefore, if the content is 1000 ppm or less, the above-mentioned effect is not affected.

<Solder paste>
There is no limitation on the contents of the solder alloy and the flux in the solder paste. 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 the present embodiment preferably contains zirconium oxide powder. Zirconium oxide can suppress an increase in viscosity of the paste due to a change with time. This is presumed to be due to the inclusion of zirconium oxide to maintain the oxide film thickness on the surface of the solder powder before it was introduced into the flux. Details are unknown, but are presumed as follows. Normally, since the active component of the flux has a slight activity even at room temperature, the surface oxide film of the solder powder is thinned by reduction, which causes the powder to agglomerate. Therefore, it is presumed that by adding zirconium oxide powder to the solder paste, the active component of the flux reacts preferentially with the zirconium oxide powder, and is maintained to such an extent that the oxide film on the surface of the solder powder does not aggregate.

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

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

  The shape of the zirconium oxide is not particularly limited. However, if the shape is zirconium oxide, the contact area with the flux is large, and there is an effect of suppressing thickening. Spherical shape provides good fluidity, and therefore excellent printability as a paste. What is necessary is just to select a shape suitably according to a desired characteristic.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

Fluxes of Examples and Comparative Examples were prepared with the compositions shown in Tables 1 to 5 below, and the flux wetting speed was verified.
The composition ratios in Tables 1 to 5 are wt (mass)% when the total amount of flux is 100.

  The solder paste contains 11% by weight of flux and 89% by weight of metal powder. The metal powder in the solder paste is a Sn-Ag-Cu-based solder alloy in which Ag is 3.0 wt%, Cu is 0.5 wt%, and the balance is Sn, and the average particle diameter of the metal powder is φ20 μm. It is.

<Evaluation of solder wettability (wetting speed)>
(1) Verification method The wetting rate of the flux is based on the meniscograph test method, and a copper plate of 5 mm width × 25 mm length × 0.5 mm thickness is oxidized at 150 ° C. for 1 hour. Then, using a Solder Checker SAT-5200 (manufactured by RHESCA) as a test device and Sn-3Ag-0.5Cu (each numerical value is mass%) as a solder, the following evaluation was performed.
First, a test plate was immersed in 5 mm of the flux of each of the example and the comparative example measured in a beaker, and the test plate was coated with the flux. Subsequently, after applying the flux, the test plate to which the flux was applied was immediately immersed in a solder bath to obtain a zero cross time (sec). Subsequently, five measurements were performed for each of the fluxes of the example and the comparative example, and the average value of the obtained five zero-cross times (sec) was calculated. The test conditions were set as follows.
Immersion speed in solder bath: 5 mm / sec (JIS Z 3198-4: 2003)
Immersion depth in solder bath: 2 mm (JIS Z 3198-4: 2003)
Immersion time in solder bath: 10 sec (JIS Z 3198-4: 2003)
Solder bath temperature: 245 ° C (JIS C 60068-2-69: 2019)
The shorter the average value of the zero cross time (sec), the higher the wetting speed and the better the solder wettability.

(2) Criteria 基準: The average value of the zero cross time (sec) is 6 seconds or less.
X: The average value of the zero cross time (sec) exceeds 6 seconds.

  In the present invention, by employing picolinic acid as the specific activator, the wetting rate was increased, and the solder wettability was able to be increased.

<Examination of solder alloy>
The flux prepared in Example A1 and a solder alloy having the alloy composition shown in Tables 6 to 11 and having a size (particle size distribution) satisfying the symbol 4 in the powder size classification (Table 2) in JIS Z 3284-1: 2014. Was mixed to produce a solder paste. The mass ratio of the flux to the solder alloy is flux: solder powder = 11: 89. For each solder paste, the change over time in viscosity was measured. In addition, the liquidus temperature and the solidus temperature of the solder powder were measured. Furthermore, the wettability was evaluated using the solder paste immediately after the preparation. Details are as follows.

(3) Change with time About each solder paste immediately after preparation, the viscosity was measured for 12 hours in the air at 25 rpm at 10 rpm using Malcom Co., Ltd .: PCU-205. If the viscosity after 12 hours is 1.2 times or less as compared to the viscosity when 30 minutes have passed since the preparation of the solder paste, it was evaluated as "O" as a sufficient thickening suppression effect was obtained, When it exceeded 1.2 times, it was evaluated as "x".

(4) ΔT
For the solder alloy before being mixed with the flux, DSC measurement was carried out using SII Nanotechnology Co., Ltd., model number: EXSTAR DSC7020 at a sample amount of about 30 mg, at a heating rate of 15 ° C./min. Temperature and liquidus temperature were obtained. ΔT was determined by subtracting the solidus temperature from the obtained liquidus temperature. When ΔT was 10 ° C. or less, “○” was evaluated, and when ΔT exceeded 10 ° C., “X” was evaluated.

(5) Wettability Each solder paste immediately after preparation was printed on a Cu plate, heated from 25 ° C. to 260 ° C. at a 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 cooled solder bumps with an optical microscope. When no unmelted solder powder was observed, it was evaluated as "O", and when unmelted solder powder was observed, it was evaluated as "x".

(6) Overall evaluation 〇: All of the above evaluations are 〇 ×: There is × in each of the above evaluations

  As shown in Tables 6 to 11, it was found that all Examples B exhibited a thickening suppressing effect, a narrowing of ΔT, and excellent wettability.

  On the other hand, Comparative Examples B1, B10, B19, B28, B37, and B46 did not contain As, and thus did not exhibit a thickening suppressing effect.

  In Comparative Examples B2, B11, B20, B29, B38, and B47, since the expression (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 showed 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 exceeded the value, the result showed that ΔT exceeded 10 ° C.

  Comparative Examples B6, B15, B24, B33, B42, and B51 showed that ΔT exceeded 10 ° C. because Equation (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 limit.

<Combination of flux and solder alloy>
In the case where various fluxes of Examples A2 to A58 were used instead of the flux of Example A1 and each of the fluxes was combined with various solder alloys of Example B, good results were obtained in the effect of suppressing thickening, ΔT, and wettability. was gotten.

Claims (7)

A flux containing a compound represented by the following general formula (1), rosin, and a solvent,
As: 25 to 300 mass ppm, Bi: 0 mass ppm or more to 25,000 mass ppm, Pb: more than 0 mass ppm to 8000 mass ppm, and the balance has an alloy composition consisting 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]
A solder alloy that satisfies
Consisting of
The flux contains the compound represented by the general formula (1) in an amount of 0.5 wt% or more and 7.0 wt% or less;
Solder paste.

[In the formula (1), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ]   The solder paste according to claim 1, wherein the compound represented by the general formula (1) is picolinic acid.   3. The solder paste according to claim 1, wherein the flux further includes a thixotropic agent.   The solder paste according to claim 3, wherein the flux contains the thixotropic agent in a total amount of 0 wt% to 15 wt%.   5. The solder paste according to claim 1, wherein the flux contains the rosin in an amount of 30 wt% or more and 60 wt% or less. 6. The flux further comprises:
Amine in a range of 0 wt% to 20 wt%,
0% to 5% by weight of an organic halogen compound;
The solder paste according to any one of claims 1 to 5, wherein the solder paste contains 0 to 2 wt% of an amine hydrohalide or 0 to 5 wt% of an antioxidant. The flux further includes an organic acid,
The solder paste according to any one of claims 1 to 6, wherein the total amount of the compound represented by the general formula (1) and the organic acid is 3 wt% or more.