JP2849216B2 - Copper and copper alloy surface treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a chemical conversion film on the surface of copper and a copper alloy, and more particularly to a method suitable for preflux treatment of a circuit portion in a hard printed circuit board and a flexible printed circuit board. To provide.

[0002]

2. Description of the Related Art A surface treatment method for forming a film of a 2-position long-chain alkylimidazole compound on the surface of copper or a copper alloy is disclosed in JP-B-46-17046 and JP-B-48-11454.
Nos. 48-25621, 49-1983, 4
Nos. 9-26183, 58-22545, 61-4
1988 and JP-A-61-90492.

As a method for forming a conversion coating of a benzimidazole compound on the surface of copper or a copper alloy, Japanese Patent Application Laid-Open No. 58-501281 discloses a treatment using 5-methylbenzimidazole. Further, a method for preventing rust of copper or copper alloy using 2-mercaptobenzimidazole is disclosed in JP-A-55-83157 and JP-A-62-77600.
And No. 63-118598.

[0004]

The surface treatment method described in Japanese Patent Application Laid-Open No. 58-501281 using 5-methylbenzimidazole has a preferable film thickness because 5-methylbenzimidazole is relatively easily dissolved in water. A conversion coating of 0.08 μm or more was not formed,
It was difficult to perform the role of protecting the underlayer during heating.

[0005] The rust prevention method described in JP-A-55-83157 and JP-A-62-77600 using 2-mercaptobenzimidazole dissolves 2-mercaptobenzimidazole in an organic solvent such as methanol and the like, This is a method of coating and drying, and has a problem in terms of adverse effects on the human body and in terms of factory security because an organic solvent is used. With respect to the method described in JP-A-63-118598,
-A three-hour immersion treatment was required to form a thin film of mercaptobenzimidazole, which was not suitable for the situation in the printed wiring board industry, which required high productivity and high speed treatment.

JP-B-46-17046 and JP-B-48-11
No. 454, No. 48-25621, No. 49-1983
No. 49-26183, No. 58-22545, No. 61-41988 and JP-A-61-90492, the surface treatment method of copper or copper alloy using a 2-position long-chain alkylimidazole compound is disclosed in Although the formed chemical conversion film has various advantages such as high water repellency and excellent rust prevention of the underlying copper, it has the following defects.

That is, it is presumed that the chemical conversion film formed by the 2-position long-chain alkylimidazole compound contains a polymerizable copper complex represented by Chemical Formula 2.

[0008]

Embedded image (R represents a long-chain alkyl group.)

Chemical conversion coatings composed of these polymerizable copper complexes generally have good heat resistance because of their polymerizability, but have the property that they are hardly soluble in various solvents and acids.

On the other hand, when soldering to a printed wiring board having the above-mentioned chemical conversion coating formed on the surface of copper, a post flux is used to improve the solderability. Post flux is usually a solution in which rosin is dissolved in a solvent such as IPA together with an activator such as an organic acid such as lactic acid or an organic halide such as glutamate hydrochloride or aniline hydrochloride. This is for dissolving a copper oxide which can be generated on the chemical conversion film or the underlying copper which is a flux film, to ensure good solderability.

However, as a measure against CFCs in recent years, so-called non-cleaning type post fluxes that do not require CFC cleaning are becoming widespread. When using a non-cleaning type post flux, there is no cleaning process after soldering, and the solid content etc. of the post flux remains on the printed circuit board. Is an essential condition that the circuit does not cause circuit corrosion, disconnection, and the like. For this reason, the activator contained in the non-cleaning type post flux is inevitably of low activity, and this technical direction is in line with the times, and is expected to continue to evolve.

The chemical conversion coating comprising the 2-position long-chain alkylimidazole compound exhibits good solderability when a conventional relatively high-activity post flux is used, but uses a low-activity post-flux. In such a case, the chemical conversion film, which is a pre-flux film, cannot be removed promptly, possibly due to the property of being insoluble in an organic solvent, an acid, or the like, and the solderability decreases. Thus, there is a demand for a pre-flux capable of obtaining good solderability even when a low-activity post-flux is used.

[0013]

Means for Solving the Problems In view of such circumstances, the present inventors have conducted intensive studies and studied and found that a benzimidazole compound having a hydrogen atom at the 1-position substituted on the surface of copper or copper alloy ( (Hereinafter referred to as a 1-substituted benzimidazole compound) and contacting with an aqueous solution containing an organic acid or an inorganic acid. It has been completed.

A typical 1-substituted benzimidazole compound used in the practice of the method of the present invention is a compound represented by the following formula:

[0015]

Embedded image (However, R ₁ represents an alkyl group, an aralkyl group or an allyl group, and R ₂ represents a hydrogen atom, an alkyl group, an aralkyl group or an aryl group.)

A typical example is 1-methyl-
2-propylbenzimidazole, 1-methyl-2-butylbenzimidazole, 1-methyl-2-pentylbenzimidazole, 1-methyl-2-hexylbenzimidazole, 1-methyl-2-heptylbenzimidazole, 1-methyl- 2-octylbenzimidazole,
1-methyl-2-nonylbenzimidazole, 1-methyl-2-undecylbenzimidazole, 1-methyl-
2-heptadecylbenzimidazole,

1-propylbenzimidazole, 1-butylbenzimidazole, 1-hexylbenzimidazole, 1-octylbenzimidazole, 1-nonylbenzimidazole, 1-undecylbenzimidazole, 1-heptadecylbenzimidazole,

1-methyl-2-phenylbenzimidazole, 1-propyl-2-phenylbenzimidazole, 1-pentyl-2-phenylbenzimidazole,
1-heptyl-2-phenylbenzimidazole, 1-
Nonyl-2-phenylbenzimidazole, 1-undecyl-2-phenylbenzimidazole,

1-propyl-2-propylbenzimidazole, 1-propyl-2-pentylbenzimidazole, 1-propyl-2-hexylbenzimidazole,
1-propyl-2-nonylbenzimidazole, 1-propyl-2-undecylbenzimidazole,

1-hexyl-2-butylbenzimidazole, 1-hexyl-2-hexylbenzimidazole, 1-hexyl-2-octylbenzimidazole,
1-hexyl-2-undecylbenzimidazole, 1-
Hexyl-2-heptadecylbenzimidazole,

1-nonyl-2-propylbenzimidazole, 1-nonyl-2-pentylbenzimidazole,
1-nonyl-2-heptylbenzimidazole, 1-nonyl-2-nonylbenzimidazole, 1-nonyl-2
-Undecylbenzimidazole, 1-nonyl-2-heptadecylbenzimidazole,

1-undecyl-2-propylbenzimidazole, 1-undecyl-2-pentylbenzimidazole, 1-undecyl-2-heptylbenzimidazole, 1-undecyl-2-nonylbenzimidazole, 1-undecyl-2-un Decylbenzimidazole, 1-undecyl-2-heptadecylbenzimidazole,

1-benzyl-2-propylbenzimidazole, 1-benzyl-2-butylbenzimidazole, 1-benzyl-2-pentylbenzimidazole,
1-benzyl-2-nonylbenzimidazole, 1-benzyl-2-undecylbenzimidazole, 1-benzyl-2-heptadecylbenzimidazole,

1-allyl-2-butylbenzimidazole, 1-allyl-2-hexylbenzimidazole, 1
-Allyl-2-octylbenzimidazole, 1-allyl-2-nonylbenzimidazole, 1-allyl-2-
Undecylbenzimidazole, 1-allyl-2-heptadecylbenzimidazole and the like.

These 1-substituted benzimidazole compounds can be synthesized by several known methods. In general, after synthesizing a 1-position unsubstituted benzimidazole compound, the 1-position is alkylated using an alkylating agent to synthesize.

The 1-substituted benzimidazole compound has 1
An unsubstituted benzimidazole compound is treated with DMF in the presence of an equimolar alkylating agent such as an alkyl halide and a dehydrohalogenating agent such as potassium hydroxide and sodium carbonate.
The reaction can be carried out in a solvent such as described above or in the absence of a solvent. Further, the 1-position unsubstituted benzimidazole compound and an alkali hydroxide such as sodium hydroxide are heated and reacted to remove water, and the 1-position unsubstituted benzimidazole compound alkali metal salt obtained by alkylation or the like is obtained. It can also be obtained by reacting with an alkylating agent in a solvent such as DMF or without a solvent.

The alkylating agent used in this case includes alkyl halides such as methyl iodide, methyl chloride, methyl bromide, benzyl chloride, allyl chloride, propyl bromide, hexyl bromide, nonyl bromide and undecyl bromide. Alternatively, a sulfate such as dimethyl sulfate is used. In addition, the 1-position unsubstituted benzimidazole compound as a raw material for the reaction is obtained by heating and reacting an o-phenylenediamine compound with a carboxylic acid.

In the practice of the method of the present invention, when a ₁ -substituted benzimidazole compound having a small total number of carbon atoms of R ₁ and R ₂ is used, a part of the chemical conversion film formed on the surface of the copper metal may not be formed. Tends to be eluted by washing with water.
₁ and the total number of carbon atoms of R ₂ is using large 1-substituted benzimidazole compounds, since a large amount of organic acid to form a treated liquid is required, the number of carbon atoms in the sum of R ₁ and R ₂ is 3 To 11 are particularly preferred.

In carrying out the method of the present invention, the 1-substituted benzimidazole compound is added in the range of 0.01 to 5%, preferably 0.1 to 2%, and the organic acid is added to add the 1-substituted benzimidazole compound. What is necessary is just to completely dissolve the imidazole compound. The organic acids used in the practice of the method of the present invention include formic acid, acetic acid, lactic acid, propionic acid, capric acid, glycolic acid, acrylic acid, benzoic acid, paranitrobenzoic acid, parabutylbenzoic acid, paranitrosulfonic acid, picric acid, Salicylic acid, m-toluic acid, oxalic acid, succinic acid, maleic acid, fumaric acid, tartaric acid, adipic acid, etc., and inorganic acids such as hydrochloric acid, phosphoric acid, nitric acid, etc.
In the range of 0.01 to 40% based on water, preferably 0.2%
What is necessary is just to add in the ratio of -20%.

In order to carry out the method of the present invention, the surface of copper or a copper alloy is subjected to a treatment such as polishing, degreasing, soft etching, and acid washing, and then the metal surface is immersed in a treatment solution or the metal surface is treated. The treatment liquid may be applied or sprayed. In the method of the present invention, 1-
The step of contacting the aqueous solution containing the substituted benzimidazole compound and an organic acid or an inorganic acid includes the step of bringing the temperature of the aqueous solution to about 2 ° C.
The contact may be performed in the range of 0 ° C. to 60 ° C. and the contact time may be 1 second to several minutes.

In the practice of the method of the present invention, a copper compound may be added to an aqueous solution containing a 1-substituted benzimidazole compound and an organic acid or an inorganic acid in order to remarkably increase the formation rate of a chemical conversion film. A zinc compound may be added to improve the heat resistance of the coating.

Representative zinc compounds that can be used in these methods include zinc oxide, zinc formate, zinc acetate, zinc oxalate, zinc lactate, zinc citrate, zinc benzoate, zinc salicylate, zinc sulfate, zinc nitrate. , Zinc phosphate, etc., and typical copper compounds include cuprous chloride, cupric chloride, copper hydroxide, copper phosphate, copper acetate, copper sulfate, copper nitrate, copper bromide, etc. In any case, it may be added in the range of 0.01 to 10%, preferably 0.02 to 5% with respect to water.

In the practice of the method of the present invention, it is also possible to form a double structure of a thermoplastic resin on the chemical conversion film to improve heat resistance. That is, after forming a conversion coating of 1-substituted benzimidazole compound on the surface of copper or copper alloy, rosin, rosin derivative such as rosin ester, terpene resin, terpene resin derivative such as terpene phenol resin or aromatic hydrocarbon resin, fatty acid A thermoplastic resin having excellent heat resistance consisting of a hydrocarbon resin such as an aromatic hydrocarbon resin or an alicyclic hydrocarbon resin or a mixture thereof is dissolved in a solvent such as toluene, ethyl acetate, or IPA, and is subjected to a roll coater method or the like. What is necessary is just to apply | coat uniformly so that it may become 1-30 micrometers in thickness on a chemical conversion film, and just to form a two-layer structure of a chemical conversion film and a thermoplastic resin.

[0034]

When a conventional aqueous solution containing a 2-position long-chain alkylimidazole compound and an organic acid is brought into contact with the surface of copper or a copper alloy, a complex-forming reaction between the 2-position long-chain alkylimidazole compound and copper and the 2-position long-chain Due to both the hydrogen bonding and the van der Waals force of the alkylimidazole compound, a conversion coating of the long-chain alkylimidazole compound at position 2 which has locally become a copper complex is formed on the copper surface. When the thus formed chemical conversion coating is left or heated, the migration of copper from the copper surface occurs, and most of the 2-position long-chain alkylimidazole compound becomes the above-mentioned polymerizable copper complex. Since this polymer-like copper complex has a high melting point and is hardly dissolved in an organic solvent, an acid, or the like, it is hardly dissolved in a low-active post-flux, and there is a concern that a soldering defect may occur during soldering.

On the other hand, when the aqueous solution containing the 1-substituted benzimidazole compound of the present invention and an organic acid or an inorganic acid is brought into contact with the surface of copper or a copper alloy, a conversion coating is formed in the same manner as in the case of the conventional 2-position long-chain alkylimidazole compound. Are formed on the copper surface. However, when an aqueous solution containing a 1-substituted benzimidazole compound is used, the hydrogen atom of NH on the imidazole ring is an alkyl group, an aralkyl group,
Since it is substituted by an allyl group or the like, a polymer-like copper complex cannot be formed, and it is presumed that a chemical conversion film composed of a low-melting-point copper complex is formed. This copper complex generally has a low melting point and is soluble in alcohols such as methanol and IPA, or ketone solvents such as acetone and MEK, and various organic and inorganic acids. However, it is considered that the chemical conversion film is easily removed, and good solderability is obtained.

[0036]

EXAMPLES The method of the present invention will be specifically described below with reference to examples and comparative examples. In these tests, the thickness of the conversion coating on the metal surface was determined by immersing a copper test piece of a predetermined size in a 0.5% hydrochloric acid aqueous solution to extract the imidazole compound, and using an ultraviolet spectrophotometer. The concentration of imidazoles contained in the extract was measured and converted into the thickness of a chemical conversion film.

For measuring the solder wetting time, a test piece (5 mm × 5 mm × 0.3 mm copper plate) was degreased and then soft-etched, followed by treatment with each treatment solution and heat treatment, and immediately before measurement, high activity Post-flux (trade name: "JS-64", manufactured by Hiroki Co., Ltd.) or low-activity post-flux (trade name: "JS-64MSS")
(Hiroki Co., Ltd.) was immersed and attached, and the solder wetting time was measured using a solder wettability tester (“SAT2000”, manufactured by Resca Co., Ltd.). The measurement condition was a solder temperature of 240 ° C. The immersion depth was 2 mm, and the immersion speed was 16 mm / min.

[0038]

Example 1 A copper plate test piece that had been degreased and soft-etched was treated with 1-hexylbenzimidazole 0.5
%, Cupric chloride 0.1% and acetic acid 5.0%
It was immersed in an aqueous solution of 3.40 at a liquid temperature of 40 ° C. for 20 seconds and washed with water. The conversion coating on the surface of the test piece thus obtained was 0.24 μm.
Was as shown in FIG.

[0039]

EXAMPLE 2 A copper plate test piece that had been degreased and soft-etched was subjected to 0.5% of 1-methyl-2-phenylbenzimidazole, 0.1% of cupric chloride and 5.0% of acetic acid.
The solution was immersed in an aqueous solution having a pH of 4.10 and containing 40 ° C. for 20 seconds, and washed with water. The conversion coating on the surface of the test piece thus obtained was 0.22 μm, and the results of the solder wettability were as shown in Table 1.

[0040]

Example 3 A copper plate test piece which had been degreased and soft-etched was subjected to 1-methyl-2-nonylbenzimidazole 0.2%, cupric chloride 0.04% and acetic acid 6.0%.
Was immersed in a pH 4.0 aqueous solution containing for 40 seconds at a liquid temperature of 50 ° C., and washed with water. The conversion coating on the surface of the test piece thus obtained was 0.23 μm, and the results of the solder wettability were as shown in Table 1.

[0041]

Example 4 A copper plate test piece which had been degreased and soft-etched was treated with 1-hexyl-2-pentylbenzimidazole 0.5%, cupric chloride 0.08% and acetic acid 9.
It was immersed in a pH 2.8 aqueous solution containing 0% at a liquid temperature of 40 ° C. for 20 seconds and washed with water. The conversion coating on the surface of the test piece thus obtained was 0.24 μm, and the results of the solder wettability were as shown in Table 1.

[0042]

Example 5 A copper plate test piece which had been degreased and soft-etched was treated with 0.5% of 1-benzyl-2-pentylbenzimidazole, 0.08% of cupric chloride and acetic acid.
It was immersed in an aqueous solution of pH 2.9 containing 0% at a liquid temperature of 40 ° C. for 40 seconds and washed with water. The conversion coating on the surface of the test piece thus obtained was 0.19 μm, and the results of the solder wettability were as shown in Table 1.

[0043]

EXAMPLE 6 A copper plate test piece subjected to a degreasing and soft etching treatment was placed in an aqueous solution of pH 2.6 containing 0.5% of 1-allyl-2-octylbenzimidazole, 0.1% of cupric chloride and 13% of acetic acid. Immersion at a liquid temperature of 40 ° C. for 22 seconds and washing with water. The conversion coating on the surface of the test piece thus obtained was 0.22 μm, and the results of the solder wettability were as shown in Table 1.

[0044]

Example 7 A brass plate test piece that had been degreased and soft-etched was immersed in the same processing solution used in Example 2 under the same conditions and washed with water. The conversion coating on the surface of the test piece thus obtained was 0.12 μm.

[0045]

Comparative Example A copper plate test piece that had been degreased and soft-etched was immersed in an aqueous solution containing 1.0% of 2-undecylimidazole and 1.6% of acetic acid at a liquid temperature of 50 ° C. for 20 seconds and washed with water. The conversion coating on the surface of the test piece thus obtained was 0.23 μm, and the results of the solder wettability were as shown in Table 1.

[0046]

[Table 1]

[0047]

According to the method of the present invention, by forming a chemical conversion film containing a 1-substituted benzimidazole compound as a main component on the surface of copper or copper alloy, even when a low-activity post flux is used, Good solderability is obtained.

Claims (2)

(57) [Claims] 1. A copper or copper alloy, wherein an aqueous solution containing a benzimidazole compound having an alkyl group, an aralkyl group or an allyl group at the first position and an organic acid or an inorganic acid is brought into contact with the surface of copper or a copper alloy. Surface treatment method. 2. A method for treating a surface of copper or a copper alloy, which comprises contacting an aqueous solution containing a benzimidazole compound represented by Chemical Formula 1 and an organic acid or an inorganic acid with the surface of copper or a copper alloy. Embedded image (However, R ₁ represents an alkyl group, an aralkyl group or an allyl group, and R ₂ represents a hydrogen atom, an alkyl group, an aralkyl group or an aryl group.)