JP5301218B2 - Surface treatment agent for copper or copper alloy and use thereof - Google Patents

Abstract

An object is to provide a surface treating agent, which in mounting electronic parts or the like to a printed wiring board using a lead-free solder, forms a chemical layer having excellent heat resistance on the surface of copper or a copper alloy constituting a circuit part of a printed wiring board or the like and at the same time, improves the wettability to the solder and makes the solderability good, and a surface treatment method. Also, another object is to provide a printed wiring board resulting from bringing the surface of copper or a copper alloy constituting a copper circuit part into contact with the foregoing surface treating agent and to provide a soldering method by bringing the surface of copper or a copper alloy into contact with the foregoing surface treating agent and then performing soldering using a lead-free solder. A surface treating agent for copper or a copper alloy, which contains an imidazole compound represented by the formula (I): (I) wherein Ar1 and Ar2 are different and represent the following formula (II) or formula (III); R represents a hydrogen atom or an alkyl group: (II) (III) wherein X1 and X2 are the same or different and represent a hydrogen atom or a chlorine atom.

Description

  The present invention relates to a surface treatment agent that can be used when soldering an electronic component or the like to copper or a copper alloy of a printed wiring board, and the use thereof.

Recently, surface mounting with improved mounting density has been widely adopted as a method for mounting printed wiring boards. Such surface mounting methods can be classified into double-sided surface mounting in which chip components are joined by cream solder, mixed mounting in which surface mounting by chip solder cream soldering and through-hole mounting of discrete components are combined. In any mounting method, since the printed wiring board is soldered a plurality of times, it is exposed to a high temperature each time and receives a severe thermal history.
As a result, the surface of the copper or copper alloy (hereinafter sometimes simply referred to as copper) constituting the circuit part of the printed wiring board is heated to promote the formation of an oxide film. It is not possible to maintain good solderability.

  In order to protect the copper circuit portion of such a printed wiring board from air oxidation, a treatment for forming a chemical conversion film on the surface of the circuit portion using a surface treatment agent is widely performed. It is required to protect the copper circuit portion without changing (deteriorating) the chemical film even after receiving the heat history of the times, thereby maintaining good solderability.

Conventionally, tin-lead alloy eutectic solder has been widely used for joining electronic components to printed wiring boards, etc., but in recent years there is concern about the harmfulness of the lead contained in the solder alloy to the human body. There is a need to use solder that does not contain lead.
For this purpose, various lead-free solders have been studied. For example, lead-free solders having a metal such as silver, zinc, bismuth, indium, antimony and copper as a base metal have been proposed.

By the way, the conventional tin-lead eutectic solder has excellent wettability with respect to the metal used for the bonding base material, particularly copper, and is firmly bonded to copper, so that the bonding property between the copper members is high. Reliability is obtained.
In contrast, lead-free solder is inferior in wettability to the copper surface compared to conventional tin-lead solder, so solderability is poor, bonding defects such as voids occur, and bonding strength is low Met.
Therefore, when using lead-free solder, selection of a solder alloy with better solderability and a flux suitable for lead-free solder is required, but surface treatment used to prevent oxidation of copper or copper alloy surfaces Also for the agent, a function of improving the wettability of the lead-free solder and improving the solderability is required.
In addition, most lead-free solders have a high melting point, and the soldering temperature is about 20 to 50 ° C. higher than that of conventional tin-lead eutectic solder. Therefore, the surface treatment agent has excellent heat resistance. It is also desired to form a chemical conversion film.

  Various imidazole compounds have been proposed as active ingredients of such surface treatment agents. For example, Patent Document 1 includes 2-alkylimidazole compounds such as 2-undecylimidazole, and Patent Document 2 includes 2-arylimidazole compounds such as 2-phenylimidazole and 2-phenyl-4-methylimidazole. Patent Document 3 discloses a 2-alkylbenzimidazole compound such as 2-nonylbenzimidazole, and Patent Document 4 discloses a 2-aralkylbenzimidazole compound such as 2- (4-chlorophenylmethyl) benzimidazole. Discloses 2-aralkylimidazole compounds such as 2- (4-chlorophenylmethyl) imidazole and 2- (2,4-dichlorophenylmethyl) 4,5-diphenylimidazole.

  However, when the surface treatment agent containing these imidazole compounds is used, the heat resistance of the chemical conversion film formed on the copper surface has not yet been satisfactory. Also, when soldering, the solder wettability is insufficient, and good solderability cannot be obtained. In particular, in the case where soldering is performed using lead-free solder instead of eutectic solder, the surface treatment agent is difficult to be practically used.

Japanese Patent Publication No.46-17046 JP-A-4-206681 Japanese Patent Laid-Open No. 5-25407 Japanese Patent Laid-Open No. 5-186888 Japanese Patent Laid-Open No. 7-243054

The present invention has been made in view of such circumstances, and when bonding electronic components or the like to a printed wiring board using lead-free solder, the copper or copper alloy of the circuit portion or the like of the printed wiring board is formed. An object of the present invention is to provide a surface treatment agent and a surface treatment method for forming a chemical conversion film having excellent heat resistance on the surface, improving wettability with solder, and improving solderability.
Also, a printed wiring board in which the surface treatment agent is brought into contact with the surface of copper or a copper alloy constituting the circuit part, and a lead-free solder is used after the surface of the copper or copper alloy is brought into contact with the surface treatment agent. An object of the present invention is to provide a soldering method for performing soldering.

As a result of intensive studies in order to solve the above-mentioned problems, the present inventors have obtained a printed wiring board having a copper circuit portion by a surface treatment agent containing an imidazole compound represented by the general formula (I) of Chemical Formula 1 Can be formed on the surface of the copper circuit portion with excellent heat resistance, that is, a chemical conversion film that can withstand the soldering temperature of lead-free solder, and when soldering using lead-free solder, The present invention has been completed by recognizing that good solderability can be obtained by improving the wettability of solder to the surface of copper or copper alloy.
That is, the first invention is a copper or copper alloy surface treatment agent characterized by containing an imidazole compound represented by the general formula (I). 2nd invention is the surface treatment method of copper or copper alloy characterized by making the surface treating agent of 1st invention contact the surface of copper or copper alloy. 3rd invention is the printed wiring board characterized by making the surface treatment agent of 1st invention contact the surface of the copper or copper alloy of a copper circuit part. A fourth invention is a soldering method, wherein the surface of copper or a copper alloy is brought into contact with the surface treatment agent of the first invention, and then soldering is performed using lead-free solder.

The surface treatment agent of the present invention can form a chemical conversion film having excellent heat resistance on the surface of copper or copper alloy constituting the circuit portion of the printed wiring board, etc., and also has the wettability of lead-free solder on the surface. It is possible to dramatically improve the solderability.
In addition, the soldering method of the present invention is useful from the viewpoint of environmental protection because it enables the use of solder that does not contain lead, which is a harmful metal.

Hereinafter, the present invention will be described in detail.
The imidazole compound used in the practice of the present invention is represented by the general formula (I) of Chemical Formula 2, and a benzyl group which may be substituted with a chlorine atom is bonded to the 2-position of the imidazole ring, whereby 4 of the imidazole ring is bonded. An imidazole compound having a naphthyl group bonded to the position, or an imidazole compound having a naphthylmethyl group bonded to the 2-position of the imidazole ring and a phenyl group optionally substituted with a chlorine atom bonded to the 4-position of the imidazole ring. The number of chlorine atoms in the case where the benzyl group or phenyl group may be substituted with a chlorine atom is preferably 1 or 2.

  R in the general formula (I) is a hydrogen atom or an alkyl group, and the alkyl group is a linear or branched saturated aliphatic group having 1 to 8 carbon atoms. Examples of such alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, etc. Is mentioned.

  The imidazole compound used in the practice of the present invention can be synthesized, for example, by employing the synthesis method shown in the reaction scheme of Chemical Formula 3.

（但し、式中のＡｒ_１、Ａｒ_２およびＲは前記と同様であり、Ｘ_３は塩素原子、臭素原子または沃素原子を表す。）

(However, Ar ₁ , Ar ₂ and R in the formula are the same as above, and X ₃ represents a chlorine atom, a bromine atom or an iodine atom.)

As an imidazole compound represented by the general formula (I) used in the practice of the present invention, when R is a hydrogen atom,
2- (1-naphthylmethyl) -4-phenylimidazole,
4- (2-chlorophenyl) -2- (1-naphthylmethyl) imidazole,
4- (3-chlorophenyl) -2- (1-naphthylmethyl) imidazole,
4- (4-chlorophenyl) -2- (1-naphthylmethyl) imidazole,
4- (2,3-dichlorophenyl) -2- (1-naphthylmethyl) imidazole,
4- (2,4-dichlorophenyl) -2- (1-naphthylmethyl) imidazole,
4- (2,5-dichlorophenyl) -2- (1-naphthylmethyl) imidazole,
4- (2,6-dichlorophenyl) -2- (1-naphthylmethyl) imidazole,
4- (3,4-dichlorophenyl) -2- (1-naphthylmethyl) imidazole,
4- (3,5-dichlorophenyl) -2- (1-naphthylmethyl) imidazole,
2- (2-naphthylmethyl) -4-phenylimidazole,
4- (2-chlorophenyl) -2- (2-naphthylmethyl) imidazole,
4- (3-chlorophenyl) -2- (2-naphthylmethyl) imidazole,
4- (4-chlorophenyl) -2- (2-naphthylmethyl) imidazole,
4- (2,3-dichlorophenyl) -2- (2-naphthylmethyl) imidazole,
4- (2,4-dichlorophenyl) -2- (2-naphthylmethyl) imidazole,
4- (2,5-dichlorophenyl) -2- (2-naphthylmethyl) imidazole,
4- (2,6-dichlorophenyl) -2- (2-naphthylmethyl) imidazole,
4- (3,4-dichlorophenyl) -2- (2-naphthylmethyl) imidazole,
4- (3,5-dichlorophenyl) -2- (2-naphthylmethyl) imidazole,
2-benzyl-4- (1-naphthyl) imidazole,
2- (2-chlorobenzyl) -4- (1-naphthyl) imidazole,
2- (3-chlorobenzyl) -4- (1-naphthyl) imidazole,
2- (4-chlorobenzyl) -4- (1-naphthyl) imidazole,
2- (2,3-dichlorobenzyl) -4- (1-naphthyl) imidazole,
2- (2,4-dichlorobenzyl) -4- (1-naphthyl) imidazole,
2- (2,5-dichlorobenzyl) -4- (1-naphthyl) imidazole,
2- (2,6-dichlorobenzyl) -4- (1-naphthyl) imidazole,
2- (3,4-dichlorobenzyl) -4- (1-naphthyl) imidazole,
2- (3,5-dichlorobenzyl) -4- (1-naphthyl) imidazole,
2-benzyl-4- (2-naphthyl) imidazole,
2- (2-chlorobenzyl) -4- (2-naphthyl) imidazole,
2- (3-chlorobenzyl) -4- (2-naphthyl) imidazole,
2- (4-chlorobenzyl) -4- (2-naphthyl) imidazole,
2- (2,3-dichlorobenzyl) -4- (2-naphthyl) imidazole,
2- (2,4-dichlorobenzyl) -4- (2-naphthyl) imidazole,
2- (2,5-dichlorobenzyl) -4- (2-naphthyl) imidazole,
2- (2,6-dichlorobenzyl) -4- (2-naphthyl) imidazole,
2- (3,4-dichlorobenzyl) -4- (2-naphthyl) imidazole,
2- (3,5-dichlorobenzyl) -4- (2-naphthyl) imidazole is mentioned.

Similarly, when R is a methyl group,
5-methyl-2- (1-naphthylmethyl) -4-phenylimidazole,
4- (2-chlorophenyl) -5-methyl-2- (1-naphthylmethyl) imidazole,
4- (3-chlorophenyl) -5-methyl-2- (1-naphthylmethyl) imidazole,
4- (4-chlorophenyl) -5-methyl-2- (1-naphthylmethyl) imidazole,
4- (2,3-dichlorophenyl) -5-methyl-2- (1-naphthylmethyl) imidazole,
4- (2,4-dichlorophenyl) -5-methyl-2- (1-naphthylmethyl) imidazole,
4- (2,5-dichlorophenyl) -5-methyl-2- (1-naphthylmethyl) imidazole,
4- (2,6-dichlorophenyl) -5-methyl-2- (1-naphthylmethyl) imidazole,
4- (3,4-dichlorophenyl) -5-methyl-2- (1-naphthylmethyl) imidazole,
4- (3,5-dichlorophenyl) -5-methyl-2- (1-naphthylmethyl) imidazole,
5-methyl-2- (2-naphthylmethyl) -4-phenylimidazole,
4- (2-chlorophenyl) -5-methyl-2- (2-naphthylmethyl) imidazole,
4- (3-chlorophenyl) -5-methyl-2- (2-naphthylmethyl) imidazole,
4- (4-chlorophenyl) -5-methyl-2- (2-naphthylmethyl) imidazole,
4- (2,3-dichlorophenyl) -5-methyl-2- (2-naphthylmethyl) imidazole,
4- (2,4-dichlorophenyl) -5-methyl-2- (2-naphthylmethyl) imidazole,
4- (2,5-dichlorophenyl) -5-methyl-2- (2-naphthylmethyl) imidazole,
4- (2,6-dichlorophenyl) -5-methyl-2- (2-naphthylmethyl) imidazole,
4- (3,4-dichlorophenyl) -5-methyl-2- (2-naphthylmethyl) imidazole,
4- (3,5-dichlorophenyl) -5-methyl-2- (2-naphthylmethyl) imidazole,
2-benzyl-5-methyl-4- (1-naphthyl) imidazole,
2- (2-chlorobenzyl) -5-methyl-4- (1-naphthyl) imidazole,
2- (3-chlorobenzyl) -5-methyl-4- (1-naphthyl) imidazole,
2- (4-chlorobenzyl) -5-methyl-4- (1-naphthyl) imidazole,
2- (2,3-dichlorobenzyl) -5-methyl-4- (1-naphthyl) imidazole,
2- (2,4-dichlorobenzyl) -5-methyl-4- (1-naphthyl) imidazole,
2- (2,5-dichlorobenzyl) -5-methyl-4- (1-naphthyl) imidazole,
2- (2,6-dichlorobenzyl) -5-methyl-4- (1-naphthyl) imidazole,
2- (3,4-dichlorobenzyl) -5-methyl-4- (1-naphthyl) imidazole,
2- (3,5-dichlorobenzyl) -5-methyl-4- (1-naphthyl) imidazole,
2-benzyl-5-methyl-4- (2-naphthyl) imidazole,
2- (2-chlorobenzyl) -5-methyl-4- (2-naphthyl) imidazole,
2- (3-chlorobenzyl) -5-methyl-4- (2-naphthyl) imidazole,
2- (4-chlorobenzyl) -5-methyl-4- (2-naphthyl) imidazole,
2- (2,3-dichlorobenzyl) -5-methyl-4- (2-naphthyl) imidazole,
2- (2,4-dichlorobenzyl) -5-methyl-4- (2-naphthyl) imidazole,
2- (2,5-dichlorobenzyl) -5-methyl-4- (2-naphthyl) imidazole,
2- (2,6-dichlorobenzyl) -5-methyl-4- (2-naphthyl) imidazole,
2- (3,4-dichlorobenzyl) -5-methyl-4- (2-naphthyl) imidazole,
2- (3,5-dichlorobenzyl) -5-methyl-4- (2-naphthyl) imidazole.

These imidazole compounds are used as an active ingredient of a surface treatment agent prepared by dissolving in water. These imidazole compounds are contained in the surface treatment agent in a proportion of 0.01 to 10% by weight, preferably in a proportion of 0.1 to 5% by weight. When the content ratio of the imidazole compound is less than 0.01% by weight, the film thickness of the chemical conversion film formed on the copper surface becomes thin, and oxidation of the copper surface cannot be sufficiently prevented. On the other hand, when the amount is more than 10% by weight, the imidazole compound remains undissolved in the surface treatment agent or may be re-precipitated even if it is completely dissolved.
In the practice of the present invention, in addition to using only one appropriate imidazole compound represented by the general formula (I), it is possible to use a combination of different imidazole compounds.

  In the practice of the present invention, an organic acid or an inorganic acid is generally used as an acid for dissolving (making an aqueous solution) an imidazole compound in water, but a small amount of an organic solvent may be used in combination. Typical organic acids used in this case include formic acid, acetic acid, propionic acid, butyric acid, glyoxylic acid, pyruvic acid, acetoacetic acid, levulinic acid, heptanoic acid, caprylic acid, capric acid, lauric acid, glycolic acid, Glyceric acid, lactic acid, acrylic acid, methoxyacetic acid, ethoxyacetic acid, propoxyacetic acid, butoxyacetic acid, 2- (2-methoxyethoxy) acetic acid, 2- [2- (2-ethoxyethoxy) ethoxy] acetic acid, 2- {2- [2- (2-Ethoxyethoxy) ethoxy] ethoxy} acetic acid, 3-methoxypropionic acid, 3-ethoxypropionic acid, 3-propoxypropionic acid, 3-butoxypropionic acid, benzoic acid, paranitrobenzoic acid, paratoluenesulfonic acid , Salicylic acid, picric acid, oxalic acid, succinic acid, maleic acid, fumaric acid, tartaric acid, Such as pin acid. Examples of the inorganic acids, hydrochloric acid, phosphoric acid, sulfuric acid, and nitric acid. These acids are contained in the surface treatment agent in a proportion of 0.1 to 50% by weight, preferably 1 to 30% by weight.

  As the organic solvent, those which are freely miscible with water such as lower alcohols such as methanol, ethanol and isopropyl alcohol or water such as acetone, N, N-dimethylformamide and ethylene glycol are suitable.

A copper compound can be added to the surface treatment agent of the present invention in order to increase the formation rate of the chemical conversion film on the surface of copper or copper alloy, and zinc can be added to further improve the heat resistance of the formed chemical conversion film. A compound may be added.
Representative examples of the copper compound include copper acetate, cuprous chloride, cupric chloride, cuprous bromide, cupric bromide, copper iodide, copper hydroxide, copper phosphate, copper sulfate. Typical examples of the zinc compound include zinc oxide, zinc formate, zinc acetate, zinc oxalate, zinc lactate, zinc citrate, zinc sulfate, zinc nitrate, zinc phosphate and the like. In any case, the surface treatment agent may contain 0.01 to 10% by weight, preferably 0.02 to 5% by weight.

  When these copper compounds and zinc compounds are used, in addition to organic or inorganic acids, substances having a buffering action such as ammonia or amines such as monoethanolamine, diethanolamine and triethanolamine are added to the solution. It is preferable to stabilize the pH.

  In the surface treatment agent of the present invention, a halogen compound is added in an amount of 0.001 to 1% by weight, preferably 0.01 to 0% in the surface treatment agent in order to further improve the formation rate of the chemical conversion film and the heat resistance of the film. .1% by weight can be added. Examples of the halogen compound include sodium fluoride, potassium fluoride, ammonium fluoride, sodium chloride, potassium chloride, ammonium chloride, sodium bromide, potassium bromide, ammonium bromide, sodium iodide, potassium iodide, and ammonium iodide. Etc.

  As conditions for treating the surface of copper or a copper alloy using the surface treatment agent of the present invention, it is preferable that the liquid temperature of the surface treatment agent is 10 to 70 ° C. and the contact time is 1 second to 10 minutes. Examples of the contact method include dipping, spraying, and application methods.

Moreover, after performing the surface treatment of this invention, it is also possible to form a double structure with a thermoplastic resin on a chemical conversion film, and to further improve heat resistance.
That is, after forming a chemical conversion film on the surface of copper or copper alloy, rosin derivatives such as rosin and rosin ester, terpene resin derivatives such as terpene resin and terpene phenol resin, aromatic hydrocarbon resin and aliphatic hydrocarbon resin A thermoplastic resin excellent in heat resistance composed of a hydrocarbon resin such as the above or a mixture thereof is dissolved in a solvent such as toluene, ethyl acetate, isopropyl alcohol, and the thickness of 1 to 30 μm on the chemical conversion film by a roll coater or the like. It is sufficient to apply uniformly to form a double structure of the chemical conversion film and the thermoplastic resin.

  Lead-free solders suitable for the practice of the present invention include Sn—Ag—Cu, Sn—Ag—Bi, Sn—Bi, Sn—Ag—Bi—In, Sn—Zn, Sn—Cu, etc. Lead-free solder is mentioned.

  In addition, the soldering method of the present invention is a flow method in which a printed wiring board is flowed over a solder bath containing heated and melted liquid solder, and soldering is performed on the joint between the electronic component and the printed wiring board, or It can be applied to the reflow method, etc., in which paste-like cream solder is printed on the printed wiring board according to the circuit pattern in advance, electronic components are mounted on the printed wiring board, the printed wiring board is heated to melt the solder, and soldering is performed. Is.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to these.
In addition, the imidazole compounds and evaluation test methods used in Examples and Comparative Examples are as follows.

[Imidazole compound]
The imidazole compounds used in the examples are as follows, and synthesis examples are shown in Reference Examples 1 to 6.
2- (1-naphthylmethyl) -4-phenylimidazole (abbreviated as “IMZ-A”)
4- (3,4-dichlorophenyl) -5-methyl-2- (1-naphthylmethyl) imidazole (abbreviated as “IMZ-B”)
2- (2-naphthylmethyl) -4-phenylimidazole (abbreviated as “IMZ-C”)
2- (4-chlorobenzyl) -4- (1-naphthyl) imidazole (abbreviated as “IMZ-D”)
2-Benzyl-4- (2-naphthyl) imidazole (abbreviated as “IMZ-E”)
2-Benzyl-5-methyl-4- (2-naphthyl) imidazole (abbreviated as “IMZ-F”)

[Reference Example 1]
<Synthesis of IMZ-A>
A suspension consisting of 33.7 g (0.15 mol) of 1-naphthylacetamidine hydrochloride, 53 g (0.38 mol) of potassium carbonate and 180 ml of N, N-dimethylformamide was stirred at 50 ° C. for 30 minutes, and then at the same temperature. Then, 30.0 g (0.15 mol) of 2-bromoacetophenone was added little by little, and the mixture was further stirred at the same temperature for 3 hours. Next, the reaction suspension was poured into 600 ml of water, extracted with toluene (100 ml × 2 times), and the toluene layer was washed with water and then concentrated under reduced pressure. The precipitated crystals were collected by filtration and filtered with a small amount of toluene. After washing and drying, a dark pink powder was obtained. The crystals were recrystallized from acetonitrile to obtain 19.3 g (0.068 mol, yield 45%) of 2- (1-naphthylmethyl) -4-phenylimidazole as a slightly pink powder.

[Reference Example 2]
<Synthesis of IMZ-B>
4- (3,4-Dichlorophenyl) -5-methyl- according to the method of Reference Example 1 except that 2-bromoacetophenone of Reference Example 1 is replaced with 2-bromo-3 ′, 4′-dichloropropiophenone. 2- (1-naphthylmethyl) imidazole was synthesized.

[Reference Example 3]
<Synthesis of IMZ-C>
2- (2-naphthylmethyl) -4-phenylimidazole was synthesized according to the method of Reference Example 1 by replacing 1-naphthylacetamidine hydrochloride of Reference Example 1 with 2-naphthylacetamidine hydrochloride.

[Reference Example 4]
<Synthesis of IMZ-D>
1-naphthylacetamidine hydrochloride of Reference Example 1 was replaced with (4-chlorophenyl) acetamidine hydrochloride and 2-bromoacetophenone was replaced with 2-bromo-1′-acetonaphthone, and 2 according to the method of Reference Example 1. -(4-Chlorobenzyl) -4- (1-naphthyl) imidazole was synthesized.

[Reference Example 5]
<Synthesis of IMZ-E>
1-naphthylacetamidine hydrochloride of Reference Example 1 was replaced with phenylacetamidine hydrochloride and 2-bromoacetophenone was replaced with 2-bromo-2'-acetonaphthone, and 2-benzyl-4 was prepared according to the method of Reference Example 1. -(2-Naphtyl) imidazole was synthesized.

[Reference Example 6]
<Synthesis of IMZ-F>
1-naphthylacetamidine hydrochloride of Reference Example 1 was replaced with phenylacetamidine hydrochloride and 2-bromoacetophenone was replaced with 2-bromo-2′-propionnaphthone, and 2-benzyl-5 according to the method of Reference Example 1. -Methyl-4- (2-naphthyl) imidazole was synthesized.

The imidazole compounds used in the comparative examples are as follows.
2-Undecylimidazole (abbreviated as “IMZ-G”, manufactured by Shikoku Kasei Kogyo Co., Ltd., trade name “Cureazole C11Z”)
・ 2-Phenylimidazole (abbreviated as “IMZ-H”, manufactured by Shikoku Kasei Kogyo Co., Ltd., trade name “Cureazole 2PZ”)
・ 2-Phenyl-4-methylimidazole (abbreviated as “IMZ-I”, manufactured by Shikoku Kasei Kogyo Co., Ltd., trade name “Curazole 2P4MZ”)
2-Nonylbenzimidazole (abbreviated as “IMZ-J”; reagent manufactured by SIGMA-ALDRICH)
2- (4-Chlorobenzyl) benzimidazole (abbreviated as “IMZ-K”; reagent manufactured by Wako Pure Chemical Industries, Ltd.)

  Chemical formulas of the imidazole compounds (IMZ-A to IMZ-F) used in the examples and the imidazole compounds (IMZ-G to IMZ-K) used in the comparative examples are shown in Chemical Formula 4 and Chemical Formula 5, respectively.

  The evaluation test methods employed in the examples and comparative examples are as follows.

[Evaluation test of solderability]
As a test piece, a printed wiring board made of glass epoxy resin of 120 mm (vertical) × 150 mm (horizontal) × 1.6 mm (thickness) having 300 copper through holes with an inner diameter of 0.80 mm was used. The test piece was degreased, soft-etched and washed with water, then immersed in a surface treatment agent maintained at a predetermined liquid temperature for a predetermined time, then washed with water and dried to a thickness of about 0.10 to 0.00 on the copper surface. A 50 μm chemical conversion film was formed.
About the test piece which performed this surface treatment, the reflow heating whose peak temperature is 240 degreeC was performed twice using the infrared reflow apparatus (Product name: MULTI-PRO-306, Vitronics company make), then, flow solder Soldering was performed using an attaching device (conveyor speed: 1.0 m / min).
The solder used was tin-lead eutectic solder (trade name: H63A, manufactured by Senju Metal Industry Co., Ltd.) having a composition of 63 tin-37 lead (weight%), and the flux used for soldering was JS- 64MSS (manufactured by Hiroki). The solder temperature was 240 ° C.
Further, the test piece subjected to the surface treatment was soldered using lead-free solder in the same manner as in the case of tin-lead eutectic solder. The solder used is a lead-free solder (trade name: H705 “Eco Solder”, manufactured by Senju Metal Industry Co., Ltd.) having a composition of 96.5 tin-3.0 silver-0.5 copper (% by weight). The flux used for attaching is JS-E-09 (manufactured by Hiroki). The peak temperature of reflow heating was 245 ° C., and the solder temperature was 245 ° C.
For the soldered test piece, the number of through holes in which the solder went up to the upper land portion of the copper through hole (soldered) was measured, and the ratio (%) to the total number of through holes (300 holes) was calculated. .
The higher the solder wettability with respect to the copper surface, the more easily the molten solder penetrates into the copper through hole and rises to the upper land portion of the through hole. That is, it is determined that the higher the ratio of the number of through holes in which the solder has reached the upper land portion with respect to the total number of through holes, the better the solder wettability with respect to copper and the better the solderability.

[Evaluation test of solder spreadability]
As a test piece, a printed wiring board made of glass epoxy resin of 50 mm (vertical) × 50 mm (horizontal) × 1.2 mm (thickness) (as a circuit pattern, a circuit part having a conductor width of 0.80 mm and a length of 20 mm made of copper foil) 10 were formed in the width direction at intervals of 1.0 mm). The test piece was degreased, soft-etched and washed with water, then immersed in a surface treatment agent maintained at a predetermined liquid temperature for a predetermined time, then washed with water and dried to a thickness of about 0.10 to 0.00 on the copper surface. A 50 μm chemical conversion film was formed.
About the test piece which performed this surface treatment, the reflow heating whose peak temperature is 240 degreeC was performed once using the infrared reflow apparatus (Product name: MULTI-PRO-306, Vitronics company make). After that, using a metal mask having an opening diameter of 1.2 mm and a thickness of 150 μm, tin-lead cream solder was printed at the center of the copper circuit portion, and reflow heating was performed under the previous conditions to perform soldering. The tin-lead cream solder used is a eutectic solder (trade name: OZ-63-330F-40-10, manufactured by Senju Metal Industry Co., Ltd.) composed of 63 tin-37 lead (% by weight).
Moreover, about the test piece which performed the said surface treatment, it soldered using the lead-free cream solder similarly to the case of a tin-lead cream solder. The lead-free cream solder used was a lead-free solder (commercial name: M705-221BM5-42-11, manufactured by Senju Metal Industry Co., Ltd.) composed of 96.5 tin-3.0 silver-0.5 copper (% by weight). ). The reflow heating performed before and after the cream solder printing was set so that the peak temperature was 245 ° C.
About the obtained test piece, the length (mm) of the solder which wet-spreaded on the copper circuit part was measured.
The larger this length, the better the solder wettability and the better the solderability.

[Example 1]
2- (1-naphthylmethyl) -4-phenylimidazole as an imidazole compound, acetic acid as an acid, copper acetate as a metal salt, and ammonium iodide as a halogen compound are dissolved in ion-exchanged water so as to have the composition shown in Table 1. Thereafter, the surface treatment agent was prepared by adjusting the pH to 2.8 with aqueous ammonia.
Next, the test piece of the printed wiring board was immersed in a surface treatment agent adjusted to 40 ° C. for 20 seconds, then washed with water and dried, and the solderability and solder spreadability were measured. These test results were as shown in Table 1.

[Examples 2 to 6]
In the same manner as in Example 1, using the imidazole compound, acid, metal salt, and halogen compound described in Table 1, a surface treatment agent having the composition described in Table 1 was prepared. Surface treatment was performed. About the obtained test piece, the solder rising property and the solder spreading property were measured. These test results were as shown in Table 1.

[Comparative Examples 1-5]
In the same manner as in Example 1, using the imidazole compound, acid, metal salt, and halogen compound described in Table 1, a surface treatment agent having the composition described in Table 1 was prepared. Surface treatment was performed. About the obtained test piece, the solder rising property and the solder spreading property were measured. These test results were as shown in Table 1.

According to the test results shown in Table 1, the surface treatment agent of the present invention is brought into contact with the copper surface of the printed wiring board to form a chemical conversion film on the copper surface, so that eutectic solder and lead-free solder on the copper surface are formed. It was recognized that the wettability was improved, and the solderability of eutectic solder and lead-free solder on the copper surface (solderability, solder spreadability) was dramatically improved. It goes without saying that the surface treatment agent of the present invention is useful when soldering using eutectic solder, but it has better wettability than eutectic solder in terms of solder wettability to copper and copper alloys. Even when soldering using inferior lead-free solder, it is sufficiently practical.

Claims (4)

A surface treatment agent for copper or copper alloy, which contains an imidazole compound represented by the general formula (I) of Chemical Formula 1.

A surface treatment method for copper or copper alloy, wherein the surface treatment agent according to claim 1 is brought into contact with the surface of copper or copper alloy. A printed wiring board, wherein the surface treatment agent according to claim 1 is brought into contact with the surface of copper or copper alloy of the copper circuit portion. A soldering method, wherein the surface of copper or a copper alloy is brought into contact with the surface treatment agent according to claim 1 and then soldered using lead-free solder.