JP7529977B2 - Flux composition containing maleic acid modified rosin ester or maleic acid modified rosin amide, flux containing same, and solder paste - Google Patents

Description

The present invention relates to a flux composition containing a maleic acid modified rosin ester or a maleic acid modified rosin amide, and a flux and a solder paste containing the same.

2. Description of the Related Art Fixing and electrical connection of electronic components in electronic equipment, such as mounting electronic components on a printed circuit board, is generally performed by soldering, which is the most advantageous method in terms of cost and reliability.
Methods commonly used for this type of soldering are the flow soldering method, in which the printed circuit board and electronic components are brought into contact with molten solder, and the reflow soldering method, in which the soldering is performed by remelting solder in the form of a solder paste, a solder preform, or a solder ball in a reflow furnace.

In this soldering process, flux is used as an auxiliary agent that helps solder adhere more easily to printed circuit boards and electronic components. Flux performs many useful functions, including: (1) cleaning the metal surface (chemically removing the oxide film on the metal surface of printed circuit boards and electronic components, cleaning the surface so that soldering is possible); (2) preventing re-oxidation (covering the cleaned metal surface during soldering to block contact with oxygen and prevent the metal surface from being re-oxidized by heating); and (3) reducing interfacial tension (reducing the surface tension of molten solder and increasing the wettability of the metal surface with solder).

Patent Document 1 describes the use of a rosin derivative compound obtained by dehydration condensation of a rosin-based carboxyl group-containing resin and a dimer acid derivative flexible alcohol compound as a soldering flux.
Furthermore, Patent Document 2 discloses a method for producing rosin ester in a short period of time with good yield.

JP 2014-185298 A JP 2017-186324 A

However, the flux described in Patent Document 1 is prone to residue cracking in the flux residue after soldering, and is therefore poor in reliability.
On the other hand, when the rosin ester described in Patent Document 2 is used as a flux, there are problems in that the activity is low and the solder wettability is poor.

In view of the above circumstances, the present invention aims to provide a soldering flux that suppresses residual cracking of flux residue and has excellent solder wettability.

As a result of intensive research aimed at solving the above problems, the inventors have discovered that the above problems can be solved by using a flux composition containing at least one selected from the group consisting of maleic acid modified rosin ester, maleic acid modified rosin amide, a hydrogenated product of the maleic acid modified rosin ester, and a hydrogenated product of the maleic acid modified rosin amide, and have thus completed the present invention. That is, the present invention is as follows.

[1]
A flux composition comprising at least one member selected from the group consisting of a maleic acid modified rosin ester, a maleic acid modified rosin amide, a hydrogenated product of the maleic acid modified rosin ester, and a hydrogenated product of the maleic acid modified rosin amide.
[2]
The flux composition according to the above-mentioned [1], wherein the maleic acid-modified rosin ester or the maleic acid-modified rosin amide is one or more selected from the group consisting of compounds represented by the following formulas (1) to (7):

（式中、Ｒは各々独立して、置換されていてもよい、直鎖若しくは分岐のアルキル基、アルキレングリコール基、又は末端変性ポリアルキレンオキシド基を示し、Ｒ’は各々独立して、置換されていてもよい、直鎖若しくは分岐のアルキレン基、又は２価のアルキレングリコール基を示す。）
［３］
上記［１］又は［２］記載のフラックス用組成物を含む、はんだ合金をはんだ付けするためのフラックス。
［４］
前記マレイン酸変性ロジンエステル及び／又はマレイン酸変性ロジンアミドの含有量が、フラックス全体に対して０ｗｔ％超６０ｗｔ％以下である、上記［３］記載のフラックス。
［５］
前記フラックスはチキソ剤をさらに含む、上記［３］又は［４］に記載のフラックス。
［６］
前記フラックスは、さらに、
アミンを０ｗｔ％以上２０ｗｔ％以下、
有機ハロゲン化合物を０ｗｔ％以上５ｗｔ％以下、
アミンハロゲン化水素酸塩を０ｗｔ％以上２ｗｔ％以下、又は
酸化防止剤を０ｗｔ％以上５ｗｔ％以下
樹脂を０ｗｔ％以上８０ｗｔ％以下、
含む、上記［３］～［５］のいずれかに記載のフラックス。
［７］
上記［３］～［６］のいずれか記載のフラックスと、はんだ合金と、を含むはんだペースト。
［８］
前記はんだ合金が、
Ａｓ：２５～３００質量ｐｐｍと、Ｐｂ：０質量ｐｐｍ超え５１００質量ｐｐｍ以下と、Ｓｂ：０質量ｐｐｍ超え３０００質量ｐｐｍ以下及びＢｉ：０質量ｐｐｍ超え１００００質量ｐｐｍ以下の少なくとも１種と、残部：Ｓｎと、からなる合金組成を有し、下記（１）式及び（２）式：
２７５≦２Ａｓ＋Ｓｂ＋Ｂｉ＋Ｐｂ （１）
０．０１≦（２Ａｓ＋Ｓｂ）／（Ｂｉ＋Ｐｂ）≦１０．００ （２）
［上記（１）式及び（２）式中、Ａｓ、Ｓｂ、Ｂｉ、及びＰｂは各々前記合金組成での含有量（質量ｐｐｍ）を表す］
を満たす、上記［７］記載のはんだペースト。

(In the formula, each R independently represents an optionally substituted linear or branched alkyl group, an alkylene glycol group, or a terminal-modified polyalkylene oxide group, and each R' independently represents an optionally substituted linear or branched alkylene group, or a divalent alkylene glycol group.)
[3]
A flux for soldering a solder alloy, comprising the flux composition according to the above [1] or [2].
[4]
The flux according to [3] above, wherein the content of the maleic acid modified rosin ester and/or the maleic acid modified rosin amide is more than 0 wt % and not more than 60 wt % based on the total weight of the flux.
[5]
The flux according to the above [3] or [4], further comprising a thixotropic agent.
[6]
The flux further comprises:
Amine is 0 wt % or more and 20 wt % or less,
Organic halogen compounds are 0 wt % or more and 5 wt % or less,
Amine hydrohalide salt is 0 wt% or more and 2 wt% or less, or antioxidant is 0 wt% or more and 5 wt% or less, and resin is 0 wt% or more and 80 wt% or less,
The flux according to any one of the above [3] to [5].
[7]
A solder paste comprising the flux according to any one of the above [3] to [6] and a solder alloy.
[8]
The solder alloy is
The alloy has an alloy composition consisting of As: 25 to 300 ppm by mass, Pb: more than 0 ppm by mass and not more than 5,100 ppm by mass, Sb: more than 0 ppm by mass and not more than 3,000 ppm by mass, and Bi: more than 0 ppm by mass and not more than 10,000 ppm by mass, and the balance: Sn, and is represented by the following formulas (1) and (2):
275≦2As+Sb+Bi+Pb (1)
0.01≦(2As+Sb)/(Bi+Pb)≦10.00 (2)
[In the above formulas (1) and (2), As, Sb, Bi, and Pb each represent the content (ppm by mass) in the alloy composition.]
The solder paste according to the above [7], which satisfies the above.

The present invention provides a soldering flux that suppresses residual cracking of flux residue and has excellent solder wettability.

The following describes in detail an embodiment of the present invention (hereinafter referred to as the "present embodiment"); however, the present invention is not limited to this embodiment, and various modifications are possible without departing from the gist of the present invention.

[Flux]
The flux for soldering the solder alloy of the present embodiment contains a flux composition including one or more members selected from the group consisting of maleic acid modified rosin ester, maleic acid modified rosin amide, a hydrogenated product of the maleic acid modified rosin ester, and a hydrogenated product of the maleic acid modified rosin amide, and a solvent.
By using the flux composition of the present embodiment, it is possible to sufficiently suppress residual cracking of the flux residue and improve the solder wettability. The flux composition can be used for both flow soldering and reflow soldering, but it is preferable to use the flux composition for reflow soldering because the effect of the present invention is more pronounced.

[Maleic acid modified rosin ester/maleic acid modified rosin amide]
The flux composition of the present embodiment contains at least one member selected from the group consisting of a maleic acid modified rosin ester, a maleic acid modified rosin amide, a hydrogenated product of the maleic acid modified rosin ester, and a hydrogenated product of the maleic acid modified rosin amide.

The maleic acid modified rosin ester is not particularly limited, and examples thereof include maleic acid modified rosin monoesters such as maleic acid modified rosin monomethyl ester, maleic acid modified rosin monoethyl ester, maleic acid modified rosin monoisopropyl ester, and maleic acid modified rosin monoethylene glycol ester; and maleic acid modified rosin diesters such as maleic acid modified rosin dimethyl ester. Among these, from the viewpoint of flux activity and compatibility, monoesters in which carboxylic acid remains are preferred, and isopropyl esters are particularly preferred.

Examples of maleic acid modified rosin esters include compounds represented by the following formula (1) or (2).

(In the formula, R represents an optionally substituted linear or branched alkyl group, an alkylene glycol group, or a terminal-modified polyalkylene oxide group.)

Here, the alkylene glycol group represents a monovalent group represented by the following formula (i), in which each R ¹ independently represents a linear or branched alkylene group having 1 to 4 carbon atoms, and n represents an integer of 1 to 500.
H-(OR ¹ ) _n - (i)

The terminal-modified polyalkylene oxide group represents a monovalent group represented by the following formula (ii), in which each R ¹ independently represents a linear or branched alkylene group having 1 to 4 carbon atoms; X represents an amino group, a linear or branched alkyl ester group having 1 to 40 carbon atoms, or a linear or branched alkyl ether group having 1 to 40 carbon atoms; and n represents an integer of 0 to 500.
X−R ¹ −(OR ¹ ) _n − (ii)

The number of carbon atoms in the alkyl group represented by R is not particularly limited, but is preferably 1 to 54. The number of carbon atoms in the alkylene glycol group and the terminal-modified polyalkylene oxide group represented by R is not particularly limited, but is preferably 1 to 500. Furthermore, in formulas (i) and (ii), the number of carbon atoms in the alkyl portion of X is preferably 1 to 24, and the number of carbon atoms in ^R1 is preferably 1 to 3. Furthermore, in formulas (i) and (ii), n is preferably 1 to 500, more preferably 1 to 100, and even more preferably 1 to 10. Examples of the terminal-modified polyalkylene oxide group include groups in which an alcohol having 1 to 40 carbon atoms, such as cetyl alcohol, stearyl alcohol, and behenyl alcohol, or a carboxylic acid having 1 to 40 carbon atoms, such as palmitic acid, stearic acid, and behenic acid, is added to the hydroxyl terminal of a polyalkylene glycol, such as polyethylene glycol, polypropylene glycol, and a copolymer of ethylene oxide and propylene oxide; and groups in which the hydroxyl terminal of a polyalkylene glycol, such as a copolymer of ethylene oxide and propylene oxide, is modified with an amino group.

The maleic acid-modified rosin ester also includes compounds in which two or more maleic acid-modified rosin esters are condensed or bonded via alcohol, etc., such as maleic acid-modified rosin ester dimers and maleic acid-modified rosin ester oligomers shown in the following formula (3).

(In the formula, R' represents an optionally substituted linear or branched alkylene group, or a divalent alkylene glycol group.)

Here, the divalent alkylene glycol group is a divalent group represented by the following formula (iii), in which R ² and R ³ each independently represent a linear or branched alkylene group having 1 to 4 carbon atoms, and n represents an integer of 0 to 500.
^-R2- ( ^OR3 ) _n- (iii)

The number of carbon atoms of the alkylene group represented by R' is not particularly limited, but is preferably 1 to 54. The number of carbon atoms of the divalent alkylene glycol group represented by R' is not particularly limited, but is preferably 1 to 500. Furthermore, in formula (iii), the number of carbon atoms of R ² and R ³ is preferably 1 to 3. Furthermore, in formula (iii), n is preferably 1 to 500, more preferably 1 to 100, and even more preferably 1 to 10.

The maleic acid modified rosin amide is not particularly limited, and examples thereof include a dehydration condensation product of maleic acid modified rosin and cyclohexylamine, and a cyclohexylamine salt of a dehydration condensation product of maleic acid modified rosin and cyclohexylamine. Specific examples include compounds represented by the following formula (4) or (5). Among these, maleic acid modified rosin monocyclohexylamide and maleic acid modified hydrogenated rosin cyclohexylamide are preferred from the viewpoint of flux activity and compatibility.

（式中、Ｒは上記と同義である。）

(In the formula, R has the same meaning as above.)

Maleic acid-modified rosin amide also includes compounds in which two or more types of maleic acid-modified rosin amide are condensed or bonded via amines, such as maleic acid-modified rosin amide dimers and maleic acid-modified rosin amide polymers, as shown in the following formula (6).

（式中、Ｒ’は上記と同義である。）

(In the formula, R′ has the same meaning as above.)

Furthermore, the maleic acid-modified rosin acid amide also includes a compound in which maleic acid-modified rosin amide and maleic acid-modified rosin ester are bonded directly or via an amine, alcohol, etc., as shown in the following formula (7).

（式中、Ｒ’は上記と同義である。）

(In the formula, R′ has the same meaning as above.)

In addition, the maleic acid modified rosin ester and maleic acid modified rosin amide also include various isomers (structural isomers, optical isomers, etc.) of the above-mentioned compounds and salts (amine salts, etc.) of the above-mentioned compounds.

The maleic acid modified rosin ester and maleic acid modified rosin amide may be used alone or in combination of two or more.

The hydrogenated maleic acid modified rosin ester and the hydrogenated maleic acid modified rosin amide refer to compounds in which the carbon-carbon double bonds present in these compounds have been hydrogenated. For example, the hydrogenated maleic acid modified rosin ester represented by the above formula (1) has a structure represented by the following formula (8).

（式中、Ｒは上記と同義である。）

(In the formula, R has the same meaning as above.)

The above-mentioned various maleic acid modified rosin esters and maleic acid modified rosin amides can be produced by known methods. Examples of known methods include the solvent-free reaction described in Example 1 of JP-A-2017-186324 and the reaction in a hydrophobic solvent described in Example 6. Examples of raw rosin used in the synthesis of maleic acid modified rosin esters and maleic acid modified rosin amides include gum rosin, tall oil rosin, wood rosin, and refined products thereof (refined rosin). Examples of raw rosin include raw pine resin and commercially available gum rosin described in "D.F.Zinkel, J.Russell, ed., Hasegawa Yoshihiro, translated (1993) Pine Chemistry: Production, Chemistry, and Uses, 361-362". That is, the maleic acid modified rosin ester and maleic acid modified rosin amide of this embodiment may include compounds obtained by esterifying or amidating rosin derivatives obtained from raw rosins such as the above-mentioned various raw rosins and (hydrogenated) maleic acid modified rosin.

The content of maleic acid modified rosin ester and maleic acid modified rosin amide is preferably more than 0 wt% and not more than 60 wt% of the entire flux, more preferably 5 wt% or more, even more preferably 10 wt% or more, even more preferably 20 wt% or more, and particularly preferably 30 wt% or more, with the upper limit being more preferably 50 wt% or less, even more preferably 40 wt% or less. The higher the content of maleic acid modified rosin ester and maleic acid modified rosin amide, the more pronounced the effect of suppressing residual cracking of flux residue tends to be.

The flux of this embodiment may contain resins other than the maleic acid modified rosin ester and maleic acid modified rosin amide described above, and their hydrogenated products. As the resin, various resins conventionally used in soldering fluxes can be used. Examples of such resins include rosin-based resins, acrylic resins, polyester, polyethylene, polypropylene, polyamide, styrene-maleic acid copolymers, acrylic resins, epoxy resins, phenolic resins, phenoxy resins, terpene resins, terpene phenolic resins, and mixtures thereof. Among these, rosin-based resins are generally used. Examples of rosin-based resins include natural rosins such as gum rosin and wood rosin, and derivatives thereof (polymerized rosin, hydrogenated rosin, disproportionated rosin, acid-modified rosin, rosin ester, etc.).

There is no limit to the resin content in the flux, and when used as a flux for reflow soldering, it can be, for example, in the range of 10 to 80 mass%, or may be in the range of 20 to 70 mass%, or may be in the range of 30 to 60 mass%. When used as a flux for flow soldering, it can be, for example, in the range of 3 to 18 mass%, or may be in the range of 6 to 15 mass%, or may be in the range of 9 to 12 mass%.

Examples of the solvent contained in the flux of this embodiment include water, alcohol-based solvents, glycol ether-based solvents, terpineols, etc. Examples of alcohol-based 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]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, etc. 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, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, etc.

The flux of the present embodiment may further contain an organic acid, an amine, or a halogen (organic halogen compound, amine hydrohalide) as an activator.
When the flux of the present embodiment is used as a flux for reflow soldering, it preferably contains 0 wt % or more and 10 wt % or less of organic acid. When the flux of the present embodiment is used as a flux for reflow soldering, it preferably contains 0 wt % or more and 20 wt % or less of amine, more preferably 0 wt % or more and 5 wt % or less of amine. When the flux of the present embodiment is used as a flux for reflow soldering, it preferably contains 0 wt % or more and 5 wt % or less of organic halogen compound as halogen, and preferably contains 0 wt % or more and 2 wt % or less of amine hydrohalide.
When the flux of this embodiment is used as a flux for flow soldering, it preferably contains an activator in an amount of 0.1 wt % or more and 12.0 wt % or less, more preferably 0.3 wt % or more and 8.0 wt % or less, and even more preferably 0.5 wt % or more and 4.0 wt % or less.

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, thioglycolic acid, terephthalic acid, dodecanedioic acid, parahydroxyphenylacetic acid, phenylsuccinic acid, phthalic acid, fumaric acid, maleic acid, malonic acid, lauric acid, benzoic acid, tartaric acid, tris(isocyanuric acid) (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, malic acid, p-anisic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, etc.

Other examples of organic acids include dimer acid, trimer acid, hydrogenated dimer acid, which is a hydrogenated product of dimer acid with hydrogen added, and hydrogenated trimer acid, which is a hydrogenated product of trimer acid with hydrogen added.

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, dimer acid which is a reaction product of methacrylic acid, trimer acid which is a reaction product of methacrylic acid, dimer acid which is a reaction product of acrylic acid and methacrylic acid, trimer acid which is a reaction product of acrylic acid and methacrylic acid, dimer acid which is a reaction product of oleic acid, 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 linolenic acid, trimer acid which is a reaction product of linolenic acid, 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 acrylic acid and linoleic acid, acrylic acid and linoleic acid. Examples of the reaction product include trimer acid, which is a reaction product of acid, dimer acid, which is a reaction product of acrylic 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 methacrylic acid and oleic acid, trimer acid, which is a reaction product of methacrylic acid and linoleic acid, dimer acid, which is a reaction product of methacrylic acid and linoleic acid, trimer acid, which is a reaction product of methacrylic acid and linoleic acid, dimer acid, which is a reaction product of methacrylic acid and linoleic acid, trimer 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 linoleic acid and linoleic acid, trimer acid, which is a reaction product of linoleic acid and linoleic acid, hydrogenated dimer acid, which is a hydrogenated product of each of the above dimer acids, and hydrogenated trimer acid, which is a hydrogenated product of each of the above trimer acids.

Amines include monoethanolamine, diphenylguanidine, ditolylguanidine, ethylamine, triethylamine, cyclohexylamine, ethylenediamine, triethylenetetramine, 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, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-di Amino-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-phenylimidazo 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-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, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenyl]benzotriazole, ethylphenol], 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-ethylhexyl)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-methylphenol, 5-methylbenzotriazole, 5-phenyltetrazole, etc.

Examples of organic halogen compounds 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, and chlorendic anhydride.

Amine hydrohalides are compounds formed by reacting an amine with a hydrogen halide.
The amine of the amine hydrohalide may be any of the amines mentioned above, and examples thereof include ethylamine, cyclohexylamine, ethylenediamine, triethylamine, diphenylguanidine, ditolylguanidine, methylimidazole, and 2-ethyl-4-methylimidazole. Examples of hydrogen halides include hydrides of chlorine, bromine, iodine, and fluorine (hydrogen chloride, hydrogen bromide, hydrogen iodide, and hydrogen fluoride). In place of or in combination with the amine hydrohalide, a boron fluoride may be contained, and examples of the boron fluoride include boron fluoroacid.
Examples of the amine hydrohalide salts include aniline hydrochloride, cyclohexylamine hydrochloride, aniline hydrobromide, diphenylguanidine hydrobromide, ditolylguanidine hydrobromide, and ethylamine hydrobromide.

The flux of this embodiment may further contain an antioxidant, such as a hindered phenol-based antioxidant. When used as a reflow soldering flux, it preferably contains 0 wt% to 5 wt% of the antioxidant, and when used as a flow soldering flux, it preferably contains 0 wt% to 5 wt%, more preferably 0 wt% to 2 wt% of the antioxidant.

The flux of the present embodiment may contain a thixotropic agent.
Examples of the thixotropic agent include wax-based thixotropic agents, amide-based thixotropic agents, and sorbitol-based thixotropic agents. Examples of the wax-based thixotropic agents include castor hardened oil. Examples of the amide-based thixotropic agents include monoamide-based thixotropic agents, bisamide-based thixotropic agents, and polyamide-based thixotropic agents, and specific examples thereof 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, p-toluenemethane amide, aromatic amide, and methylenebisstearic acid amide. Examples of the sorbitol-based thixotropic agents include dibenzylidene-D-sorbitol, bis(4-methylbenzylidene)-D-sorbitol, etc. Examples of the sorbitol-based thixotropic agents include dibenzylidene-D-sorbitol, bis(4-methylbenzylidene)-D-sorbitol, etc. Examples of the sorbitol-based thixotropic agents include dibenzylidene-D-sorbitol, bis(4-methylbenzylidene)-D-sorbitol, etc.

The flux of this embodiment may also contain an ester compound as a thixotropic agent. Examples of ester compounds include hardened castor oil.

The total amount of the thixotropic agent contained in the flux is preferably 0 wt% to 15 wt%, more preferably 0 wt% to 10 wt%, when used as a reflow soldering flux. The content of the amide-based thixotropic agent is preferably 0 wt% to 12 wt%, when used as a reflow soldering flux, and the content of the ester compound is preferably 0 wt% to 8.0 wt%, more preferably 0 wt% to 4.0 wt%, when used as a reflow soldering flux.
When used as a flow soldering flux, the total amount of the thixotropic agent contained in the flux is preferably 0 wt % or more and 3 wt % or less, and more preferably 0 wt % or more and 1 wt % or less.

[Solder paste]
The flux of the present embodiment can be used for both flow soldering and reflow soldering, but is preferably used for reflow soldering since the effects of the present invention tend to be more pronounced.

The solder paste of this embodiment contains the above-mentioned flux and a solder alloy.
The solder alloy is not particularly limited, but
The alloy has an alloy composition consisting of As: 25 to 300 ppm by mass, Pb: more than 0 ppm by mass and not more than 5,100 ppm by mass, Sb: more than 0 ppm by mass and not more than 3,000 ppm by mass, and Bi: more than 0 ppm by mass and not more than 10,000 ppm by mass, and the balance: Sn, and is represented by the following formulas (1) and (2):
275≦2As+Sb+Bi+Pb (1)
0.01≦(2As+Sb)/(Bi+Pb)≦10.00 (2)
[In the above formulas (1) and (2), As, Sb, Bi, and Pb each represent the content (ppm by mass) in the alloy composition.]
It is preferable that the following is satisfied.

As is an element that can suppress the change in viscosity of the solder paste over time. As has low reactivity with flux and is a noble element relative to Sn, so it is presumed that it can exert a thickening suppression effect. If As is less than 25 ppm by mass, the thickening suppression effect cannot be fully exerted. 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 there is too much As, 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.

Sb is an element that has low reactivity with flux and exhibits a thickening suppression effect. When the solder alloy according to this embodiment contains Sb, the lower limit of the Sb content is more than 0 mass ppm, preferably 25 mass ppm or more, more preferably 50 mass ppm or more, even more preferably 100 mass ppm or more, and particularly preferably 300 mass ppm or more. On the other hand, if the Sb content is too high, wettability deteriorates, so the content must be moderate. The upper limit of the Sb content is 3000 mass ppm or less, preferably 1150 mass ppm or less, and more preferably 500 mass ppm or less.

Bi and Pb, like Sb, are elements that have low reactivity with flux and suppress thickening. In addition, Bi and Pb lower the liquidus temperature of the solder alloy and reduce the viscosity of the molten solder, so they are elements that can suppress the deterioration of wettability caused by As.

If at least one element of Sb, Bi, and Pb is present, the deterioration of wettability due to As can be suppressed. When the solder alloy according to this 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, even more preferably 75 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 this 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, even more preferably 75 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 high, the solidus temperature drops significantly, and ΔT, the temperature difference between the liquidus temperature and the solidus temperature, becomes too wide. If ΔT is too wide, a high-melting-point crystalline phase with a low content of Bi and Pb precipitates during the solidification process of the molten solder, concentrating Bi and Pb in the liquid phase. If the temperature of the molten solder then drops further, the low-melting-point crystalline phase with a high concentration of Bi and Pb segregates. This causes the mechanical strength of the solder alloy to deteriorate, resulting in poor reliability. In particular, since a crystalline phase with a high concentration of Bi is hard and brittle, segregation in the solder alloy significantly reduces reliability.

From this viewpoint, when the solder alloy according to this embodiment contains Bi, the upper limit of the Bi content is 10,000 ppm by mass or less, preferably 1,000 ppm by mass or less, more preferably 600 ppm by mass or less, and even more preferably 500 ppm by mass or less. When the solder alloy according to this embodiment contains Pb, the upper limit of the Pb content is 5,100 ppm by mass or less, preferably 5,000 ppm by mass or less, more preferably 1,000 ppm by mass or less, even more preferably 850 ppm by mass or less, and particularly preferably 500 ppm by mass or less.

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

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

As, Sb, Bi and Pb are all elements that exhibit a thickening suppression effect. The total of these must be 275 mass ppm or more. In formula (1), the As content is doubled because As has a stronger thickening suppression effect than Sb, Bi and Pb.

If formula (1) is less than 275, the thickening suppression effect is not fully exerted. The lower limit of formula (1) is 275 or more, preferably 350 or more, and more preferably 1200 or more. On the other hand, the upper limit of formula (1) is not particularly limited from the viewpoint of the thickening suppression effect, but from the viewpoint of keeping ΔT in an appropriate range, it is preferably 25200 or less, more preferably 10200 or less, even more preferably 5300 or less, and particularly preferably 3800 or less.

The upper and lower limits of the above preferred embodiments are appropriately selected to give the following formulas (1a) and (1b).

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

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

0.01≦(2As+Sb)/(Bi+Pb)≦10.00 (2)
In the above formula (2), As, Sb, Bi, and Pb each represent the content (ppm by mass) in the alloy composition.

The wettability of the solder alloy deteriorates when the content of As and Sb is high. On the other hand, Bi and Pb suppress the deterioration of wettability due to the inclusion of As, but if the content is too high, ΔT increases, so strict management is required. In particular, in an alloy composition that simultaneously contains Bi and Pb, ΔT is likely to increase. In view of this, if the content of Bi and Pb is increased to excessively improve wettability, ΔT will widen. On the other hand, if the content of As or Sb is increased to improve the thickening suppression effect, wettability will deteriorate. Therefore, in this embodiment, the elements are divided into a group of As and Sb and a group of Bi and Pb, and when the total amount of both groups is within a proper predetermined range, the thickening suppression effect, narrowing of ΔT, and wettability are all satisfied simultaneously.

If formula (2) is less than 0.01, the total content of Bi and Pb is relatively larger than the total content of As and Pb, and ΔT is widened. The lower limit of formula (2) is 0.01 or more, preferably 0.02 or more, more preferably 0.41 or more, even more preferably 0.90 or more, particularly preferably 1.00 or more, and most preferably 1.40 or more. On the other hand, if formula (2) exceeds 10.00, the total content of As and Sb is relatively larger than the total content of Bi and Pb, and wettability is deteriorated. The upper limit of formula (2) is 10.00 or less, preferably 5.33 or less, more preferably 4.50 or less, even more preferably 2.67 or less, even more preferably 4.18 or less, and particularly preferably 2.30 or less.

The denominator of formula (2) is "Bi + Pb", and formula (2) does not hold if these elements are not contained. In other words, the solder alloy according to this embodiment necessarily contains at least one of Bi and Pb. As described above, an alloy composition that does not contain Bi and Pb has poor wettability.
The above preferred embodiments are represented by the following formula (2a), with the upper and lower limits appropriately selected.

0.31≦(2As+Sb)/(Bi+Pb)≦10.00 (2a)
In the above formula (2a), As, Sb, Bi and Pb each represent the content (ppm by mass) in the alloy composition.

Ag is an optional element that can form Ag ₃ Sn at the crystal interface to improve the reliability of the solder alloy. Ag is also an element with a higher ionization tendency than Sn, and its coexistence with As, Pb, and Bi promotes the effect of suppressing thickening of these elements. 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. In addition, Cu has a more noble ionization tendency than Sn, and its coexistence with As, Pb, and Bi promotes the thickening suppression effect 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 balance of the solder alloy according to this embodiment is Sn. In addition to the above elements, the solder alloy may contain unavoidable impurities. Even if unavoidable impurities are contained, the above-mentioned effects are not affected. Furthermore, as described below, even if an element that is not contained in this embodiment is contained as an unavoidable impurity, the above-mentioned effects are not affected. If the In content is too high, ΔT will increase, so if the content is 1000 ppm by mass or less, the above-mentioned effects are not affected.

There is no limit to the content of the solder alloy and flux in the solder paste; for example, the solder alloy can be 5 to 95 wt % and the flux can be 5 to 95 wt %.

The solder paste according to the present embodiment preferably contains zirconium oxide powder. Zirconium oxide can suppress the increase in viscosity of the paste over time. It is presumed that the zirconium oxide content maintains the oxide film thickness on the surface of the solder powder in the state it was in before it was added to the flux. Although the details are unclear, it is presumed as follows. Normally, the active components of the flux are slightly active even at room temperature, so the oxide film on the surface of the solder powder becomes thinner due to reduction, which causes the powder to aggregate. Therefore, it is presumed that by adding zirconium oxide powder to the solder paste, the active components of the flux react preferentially with the zirconium oxide powder, and the oxide film on the surface of the solder powder is maintained to a level that does not aggregate.

To fully exert these effects, the content of zirconium oxide powder in the solder paste is preferably 0.05 to 20.0% of the total mass of the solder paste. If it is 0.05% or more, the above effects can be exerted, and if it is 20.0% or less, the content of metal powder can be secured and the effect of preventing thickening can be exerted. The content of zirconium oxide is preferably 0.05 to 10.0%, and more preferably 0.1 to 3%.

The particle size of the zirconium oxide powder in the solder paste is preferably 5 μm or less. If the particle size is 5 μm or less, the printability of the paste can be maintained. There is no particular lower limit, but it should be 0.5 μm or more. The above particle size was determined by taking an SEM photograph of the zirconium oxide powder, determining the projected circle equivalent diameter for each powder of 0.1 μm or more by image analysis, and averaging the results.

The shape of zirconium oxide is not particularly limited, but irregular shapes have a large contact area with the flux and are effective in suppressing thickening. Spherical shapes provide good fluidity and therefore excellent printability as a paste. The shape can be selected appropriately depending on the desired characteristics.

The present invention will be described in more detail below using examples and comparative examples, but the technical scope of the present invention is not limited to these.

Fluxes of Examples A1 to A45 and Comparative Examples A1 to A3 were prepared according to the compositions shown in Tables 1 to 6 below, and solder pastes were prepared using these fluxes to verify the wetting speed of the fluxes.
In addition, the composition ratios in the following tables are wt (mass) % when the total amount of the flux is taken as 100.

The solder paste is 11 wt% flux and 89 wt% metal powder. The metal powder in the solder paste is a Sn-Ag-Cu solder alloy that is 3.0 wt% Ag, 0.5 wt% Cu, and the remainder Sn, and the average grain size of the metal powder is φ20 μm.

<Flux considerations>
(1) Evaluation of solder wettability (wetting speed) (verification method)
The wetting speed of the solder paste was evaluated in accordance with the meniscograph test method, in which a copper plate with a width of 5 mm, a length of 25 mm, and a thickness of 0.5 mm was oxidized at 150° C. for 1 hour to obtain a copper oxide plate as a test plate. The test device was Solder Checker SAT-5200 (manufactured by RHESCA) and the solder was Sn-3Ag-0.5Cu (each value is by wt %), as follows:
First, a test plate was immersed 5 mm into each of the fluxes of the Examples and Comparative Examples measured in a beaker, and the flux was applied to the test plate. Then, after applying the flux, the test plate to which the flux was applied was immediately immersed in a solder bath to obtain the zero cross time (sec). Then, five measurements were performed for each of the fluxes of the Examples and Comparative Examples, and the average value of the five obtained 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, which means better solder wettability.

(Judgment criteria)
A: The average value of the zero cross time (sec) is 6 seconds or less.
×: The average value of the zero cross time (sec) exceeds 6 seconds.

(2) Evaluation of Residual Crack Inhibition A paste was printed using a 0.15 mm thick metal mask on a substrate with 64 rows of electrode pads, each 1.5 x 0.25 mm in size, arranged at a pitch of 0.4 mm, and soldered using a reflow furnace (reflow peak temperature: 240° C.). After reflow, the substrate was left in a room temperature environment for 24 hours or more, and the number of cracks in the flux residue between the pads was counted and evaluated as follows.
◯: 15 or less residue cracks ×: More than 15 residue cracks

The maleic acid modified rosin ester and maleic acid modified rosin amide compounds in the table all include their isomers (structural isomers and stereoisomers).

The flux of this embodiment contains at least one selected from the group consisting of maleic acid modified rosin ester, maleic acid modified rosin amide, hydrogenated maleic acid modified rosin ester, and hydrogenated maleic acid modified rosin amide, thereby suppressing residual cracking of the flux residue and also exhibiting excellent solder wettability.

<Solder alloy considerations>
The flux prepared in Example A1 was mixed with a solder alloy having the alloy composition shown in Tables 7 to 12 and a size (particle size distribution) that satisfies symbol 4 in the powder size classification (Table 2) in JIS Z 3284-1:2014 to prepare a solder paste. The mass ratio of the flux to the solder alloy was flux:solder powder=11:89. The change in viscosity over time was measured for each solder paste. In addition, the liquidus temperature and solidus temperature of the solder powder were measured. Furthermore, wettability was evaluated using the solder paste immediately after preparation. The details are as follows.

(3) Change over time For each solder paste immediately after preparation, the viscosity was measured for 12 hours in the atmosphere at 25° C., at a rotation speed of 10 rpm, using a PCU-205 manufactured by Malcom Co., Ltd. If the viscosity after 12 hours was 1.2 times or less compared to the viscosity 30 minutes after preparation of the solder paste, it was evaluated as "○" as a sufficient thickening suppression effect was obtained, and if it exceeded 1.2 times, it was evaluated as "×".

(4) ΔT
The solder alloy before mixing with the flux was subjected to DSC measurement using an EXSTAR DSC7020 manufactured by SII Nanotechnology Co., Ltd., with a sample amount of about 30 mg and a heating rate of 15°C/min to obtain the solidus temperature and liquidus temperature. The solidus temperature was subtracted from the obtained liquidus temperature to obtain ΔT. When ΔT was 10°C or less, it was evaluated as "○", and when it exceeded 10°C, it was evaluated as "×".

(5) Wettability Each solder paste immediately after preparation was printed on a Cu plate, heated in a _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. The wettability was evaluated by observing the appearance of the solder bumps after cooling with an optical microscope. When no incompletely melted solder powder was observed, it was evaluated as "○", and when incompletely melted solder powder was observed, it was evaluated as "×".

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

As shown in Tables 7 to 12, all of Example B exhibited a thickening suppression effect, narrowing of ΔT, and excellent wettability.

In contrast, Comparative Examples B1, B14, B27, B40, B53, and B66 did not exhibit the thickening suppression effect because they did not contain As.

Comparative examples B2, B15, B28, B41, B54, and B67 did not exhibit the thickening suppression effect because the formula (1) was below the lower limit.

Comparative examples B3, B16, B29, B42, B55, and B68 had poor wettability because the formula (2) exceeded the upper limit.

Comparative examples B4, B5, B17, B18, B30, B31, B43, B44, B56, B57, B69, and B70 showed poor wettability because the As content and formula (2) exceeded the upper limit.

Comparative Examples B6 to B8, B19 to B21, B32 to B34, B45 to B47, B58 to B60, and B71 to B73 had poor wettability because the Sb content exceeded the upper limit.

Comparative examples B9, B10, B22, B23, B35, B36, B48, B49, B61, B62, B74, and B75 showed ΔT exceeding 10°C because the Bi content exceeded the upper limit.

Comparative Examples B11, B13, B24, B26, B37, B39, B50, B52, B63, B65, B76, and B78 showed ΔT exceeding 10°C because the Pb content exceeded the upper limit.

Comparative examples B12, B25, B38, B51, B64, and B77 did not contain Bi or Pb, and therefore formula (2) did not hold, and therefore had poor wettability.

<Combination of flux and solder alloy>

When the various fluxes of Examples A2 to A45 were used instead of the flux of Example A1 and combined with the various solder alloys of Example B, good results were obtained in terms of the thickening inhibition effect, ΔT, and wettability.

<Preparation of flux composition for flow soldering>
Flux compositions for flow soldering of Reference Examples C1 to C36 were prepared according to the compositions shown in Tables 13 to 15 below.

The flux of this embodiment suppresses flux residue cracking and has excellent solder wettability, even when used as a flow soldering flux.

Claims (5)

a flux composition comprising at least one member selected from the group consisting of a maleic acid modified rosin ester, a maleic acid modified rosin amide, a hydrogenated product of the maleic acid modified rosin ester, and a hydrogenated product of the maleic acid modified rosin amide ;
A thixotropic agent,
Flux for soldering solder alloys. 2. The flux according to claim 1 , wherein the content of the maleic acid modified rosin ester and/or the maleic acid modified rosin amide is more than 0 wt % and not more than 60 wt % based on the total weight of the flux. The flux further comprises:
Amine is 0 wt % or more and 20 wt % or less,
Organic halogen compounds are 0 wt % or more and 5 wt % or less,
Amine hydrohalide salt is 0 wt% or more and 2 wt% or less, or antioxidant is 0 wt% or more and 5 wt% or less, and resin is 0 wt% or more and 80 wt% or less,
The flux according to claim 1 or 2 , comprising: A solder paste comprising the flux according to any one of claims 1 to 3 and a solder alloy. The solder alloy is
The alloy has an alloy composition consisting of As: 25 to 300 ppm by mass, Pb: more than 0 ppm by mass and not more than 5,100 ppm by mass, Sb: more than 0 ppm by mass and not more than 3,000 ppm by mass, and Bi: more than 0 ppm by mass and not more than 10,000 ppm by mass, and the balance: Sn, and is represented by the following formulas (1) and (2):
275≦2As+Sb+Bi+Pb (1)
0.01≦(2As+Sb)/(Bi+Pb)≦10.00 (2)
[In the above formulas (1) and (2), As, Sb, Bi, and Pb each represent the content (ppm by mass) in the alloy composition.]
The solder paste according to claim 4 , which satisfies the above.