JPH05345984A - Surface treating agent for copper and copper alloy - Google Patents

Abstract

PURPOSE:To obtain the chemical conversion film excellent in rust preventing property and thermal resistance by specifying the benzimidazole compd. which is contained in the pre-fluxing agent used at the copper circuit part of the hard and flexible printed circuit plate. CONSTITUTION:This surface treating agent contains 2-(cyclohexylalkyl) benzimidazole compd. (B) expressed by the formula as active component. In the formula, n is 0-6, each of R1, R2 is H atom, lower alkyl group or halogen atom and may be the same or different with each other. By allowing to contact the aq. soln. of this surface treating agent with the surface of copper or copper alloy, the chemical conversion film of compd. B which is locally formed into a copper complex is obtained. By allowing to stand or by heating this chemical conversion film, the compd. B is changed to the described copper complex, and thermally and chemically stable film is obtained. Further, because the compd. B is hardly soluble in water, the compd. B is dissolved using an acid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous surface treatment agent for forming a chemical conversion film on the surfaces of copper and copper alloys, and particularly to a pre-flux of a copper circuit portion in a hard printed wiring board and a flexible printed wiring board. It is suitable as a treating agent.

[0002]

2. Description of the Related Art As 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, Japanese Patent Publication Nos. 46-17046, 48-11454 and 48-2 are available.
No. 5621, No. 49-1983, No. 49-26183, No. 58-22545,
No. 61-41988 and JP-A No. 61-90492.

As a method for forming a chemical conversion coating film of a benzimidazole compound on the surface of copper or copper alloy,
A treatment method using 5-methylbenzimidazole is disclosed in JP-A-58-501281, and a treatment method using 2-alkylbenzimidazoles is disclosed in JP-A-4-72072 and 4-80375.
And 4-99285. In addition, a method of rust prevention of copper or copper alloy using mercaptobenzimidazole, JP-A-55-83157, 62-77600 and 63-118.
It is disclosed in Japanese Patent No. 598.

[0004]

Recently, as a method of joining electronic components to a printed wiring board, a surface mounting method has come to be widely used, and temporary mounting of chip components, double-sided mounting of component devices or chip components and discrete components. Printed wiring boards have come to be exposed to high temperatures due to mixed components.

When a surface treatment of a printed wiring board is performed using a conventionally known 2-position long-chain alkylimidazole compound, the surface-treated copper surface is discolored when exposed to high temperature, and the soldering is performed thereafter. There was a risk of trouble. Further, in the treatment method using 5-methylbenzimidazole described in JP-A-58-501281, since this compound is relatively soluble in water, a chemical conversion film of 0.08 μm or more, which is recognized as a preferable film thickness, is formed. I can't
There was a drawback that it was difficult to protect the copper base under high temperature.

Further, the rust-preventing method using 2-mercaptobenzimidazole described in JP-A-55-83157 and JP-A-62-77600 is a method in which 2-mercaptobenzimidazole is dissolved in an organic solvent such as methanol to give a base solution. It is a method of applying it to a material and drying it. Since it uses an organic solvent, it has a bad effect on the human body and has a problem in safety of the factory. According to the method described in Japanese Patent Laid-Open No. 63-118598, a printed wiring that requires a high productivity and a high-speed treatment requires a dipping treatment for about 3 hours to form a thin film of 2-mercaptobenzimidazole. It did not fit the actual situation of the board industry.

When 2-alkylbenzimidazoles described in JP-A-4-72072, JP-A-4-80375 and JP-A-4-99285 are used, a 2-position long-chain alkylimidazole compound is used. Compared with the case, the solderability after exposure to high temperature is significantly improved, but it is still not sufficiently satisfactory.

As described above, the pre-flux which can be applied to the surface mounting method of the printed wiring board and has a high heat resistance and does not deteriorate the working environment, that is, an aqueous solution-based pre-flux which is excellent in solderability even after being exposed to a high temperature. Was desired.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in view of such circumstances, and as a result, on the surface of copper or a copper alloy, a 2- (cyclohexylalkyl) benzimidazole compound represented by Chemical formula 1 It was found that a chemical conversion coating film excellent in rust prevention and heat resistance is formed by contacting with an aqueous solution surface treatment agent containing as an active ingredient, and the present invention has been completed.

[0010]

[Chemical 1]

(Where n is an integer from 0 to 6 and R is
₁ and R ₂ are the same or different and each represents a hydrogen atom, a lower alkyl group or a halogen atom. )

The 2- (cyclohexylalkyl) benzimidazole compounds suitable for carrying out the method of the present invention include:
2-cyclohexylbenzimidazole, 2- (cyclohexylmethyl) benzimidazole, 2- (2-cyclohexylethyl) benzimidazole, 2- (3-cyclohexylpropyl) benzimidazole, 2- (4
-Cyclohexylbutyl) benzimidazole, 2-
(5-cyclohexylbenzyl) benzimidazole,
2- (6-cyclohexylhexyl) benzimidazole, 2-cyclohexyl-5-methylbenzimidazole, 2- (cyclohexylmethyl) -5-methylbenzimidazole, 2- (2-cyclohexylethyl) -5
-Methylbenzimidazole, 2- (3-cyclohexylpropyl) -5-methylbenzimidazole, 2-
(4-Cyclohexylbutyl) -5-methylbenzimidazole, 2- (5-cyclohexylpentyl) -5-
Methylbenzimidazole, 2- (6-cyclohexylhexyl) -5-methylbenzimidazole, 2-cyclohexyl-5,6-dimethylbenzimidazole, 2
-(Cyclohexylmethyl) -5,6-dimethylbenzimidazole, 2- (2-cyclohexylethyl)-
5,6-Dimethylbenzimidazole, 2- (3-cyclohexylpropyl) -5,6-dimethylbenzimidazole, 2- (4-cyclohexylbutyl) -5,6-
Dimethylbenzimidazole, 2- (5-cyclohexylpentyl) -5,6-dimethylbenzimidazole,
2- (6-cyclohexylhexyl) -5,6-dimethylbenzimidazole, 2-cyclohexyl-5-chlorobenzimidazole, 2- (cyclohexylmethyl)
-5-chlorobenzimidazole, 2- (cyclohexylethyl) -5-chlorobenzimidazole, 2- (3
-Cyclohexylpropyl) -5-chlorobenzimidazole, 2- (4- (cyclohexylbutyl) -5-chlorobenzimidazole, 2- (5- (cyclohexylpentyl) -5-chlorobenzimidazole, 2- (6
-(Cyclohexylhexyl) -5-chlorobenzimidazole and the like, and these 2- (cyclohexylalkyl) benzimidazole compounds can be synthesized by a known method.

That is, it can be obtained by reacting an orthophenylenediamine compound with a cyclohexanecarboxylic acid or a fatty acid having a cyclohexyl group. This is shown in the following reaction formula.

[0014]

[Chemical 2]

(In the formula, n, R ₁ and R ₂ are the same as above.)
In the practice of the present invention, a 2- (cyclohexylalkyl) benzimidazole compound was added as an active ingredient in an amount of 0.01
An aqueous solution type surface treatment agent is used which is contained in a proportion of from 10 to 10% by weight, preferably from 0.1 to 5% by weight.

Since the 2- (cyclohexylalkyl) benzimidazole compound is poorly soluble in water, it is made into an aqueous solution by using an organic acid or an inorganic acid. Further, a 2- (cyclohexyl) alkylbenzimidazole compound may be made into an aqueous solution by using an organic solvent miscible with water together with an organic acid or an inorganic acid. Note that the above chemical formula 1
The 2- (cyclohexylalkyl) benzimidazole compound represented by is not suitable for practical use when n in the formula is 7 or more because the solubility in water is significantly reduced.

Organic acids used in this case include formic acid, acetic acid, propionic acid, butyric acid, capric acid, glycolic acid, lactic acid, acrylic acid, benzoic acid, paranitrobenzoic acid, paratoluenesulfonic acid, salicylic acid, picric acid, Oxalic acid, succinic acid, maleic acid, fumaric acid, tartaric acid, adipic acid and the like, and inorganic acids include hydrochloric acid, phosphoric acid, sulfuric acid, nitric acid and the like. These acids are contained in an amount of 0.01 to 40% by weight, preferably 0.2 to 2 with respect to the aqueous solution.
It suffices to add it in a proportion of 0% by weight.

As the organic solvent used at this time, lower alcohols such as methanol, ethanol and isopropyl alcohol, and water such as acetone and N, N-dimethylformamide can be mixed.

The condition for treating the surface of copper or copper alloy with the surface treating agent of the present invention is that the temperature of the treating agent is about 20.degree.
Appropriately, the contact time is from 1 second to 10 minutes at -60 ° C. The contact method includes dipping, spraying, coating and the like.

When used in the surface treatment agent of the present invention, a copper compound may be added to increase the rate of formation of a chemical conversion coating on a metal surface, and a zinc compound may be added to improve the heat resistance of the formed chemical conversion coating. May be added.

Typical copper compounds that can be used in the above method are cuprous chloride, cupric chloride, copper hydroxide, copper phosphate, copper acetate, copper sulfate, copper nitrate, copper bromide and the like. Further, 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, etc. On the other hand, 0.01 to 10% by weight, preferably 0.02 to 5% by weight may be added.

As described above, when using a copper compound or a zinc compound, it is possible to stabilize the pH of the solution by adding a substance having a buffering action such as ammonia or amines in addition to the organic acid or the inorganic acid. desirable. Further, in carrying out 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 a 2- (cyclohexylalkyl) benzimidazole compound on the surface of copper or a copper alloy, a rosin derivative such as rosin or rosin ester, a terpene resin derivative such as a terpene resin or a terpene phenol resin, or an aroma. A thermoplastic resin having excellent heat resistance composed of a hydrocarbon resin such as an aromatic hydrocarbon resin, an aliphatic hydrocarbon resin, an alicyclic hydrocarbon resin or a mixture thereof is dissolved in a solvent such as toluene, ethyl acetate or IPA. , 1 to 30 on the chemical conversion film by roll coater method, etc.
The two-layer structure of the chemical conversion coating and the thermoplastic resin may be formed by uniformly coating the coating so as to have a thickness of μm.

[0024]

[Function] As an active ingredient on the surface of copper or copper alloy, 2-
When an aqueous surface treatment agent containing a (cyclohexylalkyl) benzimidazole compound is brought into contact,
2- (Cyclohexylalkyl) was locally converted to a copper complex by the complex formation reaction of the (cyclohexylalkyl) benzimidazole compound with copper and the hydrogen bond between the 2- (cyclohexylalkyl) benzimidazole compound and the Van der Waals force. A conversion coating of an alkyl) benzimidazole compound is formed on the copper or copper alloy surface.

When the above chemical conversion coating is left standing or heated, copper is transferred from the copper surface, and most of the 2- (cyclohexylalkyl) benzimidazole compound becomes a copper complex of the 2- (cyclohexylalkyl) benzimidazole compound. .. The chemical conversion coating consisting of the above copper complex is stable both thermally and chemically, and can protect the underlying copper or copper alloy from oxidation due to exposure to high temperatures and from rust due to long-term storage. is there.

[0026]

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 chemical 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 a 2- (cyclohexylalkyl) benzimidazole compound,
Using an ultraviolet spectrophotometer, 2-
The concentration of the (cyclohexylalkyl) benzimidazole compound was measured and converted into the thickness of the chemical conversion film.

The solder wetting time was measured by using a copper plate or a brass plate having a size of 5 mm × 50 mm × 0.3 mm as a test piece. The test piece was degreased, soft-etched, and then dipped with each treatment agent. After that, a chemical conversion film is formed on the surface of the test piece, and the test piece is allowed to stand under each predetermined condition, and after the test piece is heat-treated, it is dipped and attached to Postflux (trade name: "JS-64", manufactured by Hiroki Co., Ltd.),
The solder wetting time was measured. In the measurement, a solder wettability tester (“SAT2000”, manufactured by Reska Co., Ltd.) was used, and the measurement conditions were a solder temperature of 250 ° C., an immersion depth of 2 mm, and an immersion speed of 16 mm / sec.

A test piece of a copper plate was degreased, soft-etched, washed with water, and immersed in a surface treatment agent having the composition shown in Table 1 at a predetermined temperature for a predetermined time.
It was taken out, washed with water and dried to form a 0.25 μm chemical conversion coating on the surface of each test piece. After leaving the test piece subjected to the film formation treatment under the conditions shown in Table 1,
Further heat treatment was performed, and the solder wetting time thereafter was measured. The heat treatment was performed in a hot air oven at 120 ° C. for 5 minutes and at a vapor phase of 215 ° C.
-70 "), the operation of heating each for 5 minutes was alternately repeated three times.

Example 1 A test piece was treated with a surface treatment agent containing 2- (cyclohexylalkyl) benzimidazole (0.50% by weight), formic acid (0.75% by weight) and copper acetate (0.0%).
After dipping in a 6 wt% aqueous solution for 180 seconds at a liquid temperature of 50 ° C., it was taken out, washed with water and dried. After that, the sample was left to stand under the conditions shown in Table 1 and subjected to a heat treatment. As a result, the solder wettability measurement results were as shown in Table 1.

(Example 2) The test piece was treated with 2- (cyclohexylmethyl) benzimidazole (0.1%) as the surface treatment agent.
In an aqueous solution consisting of 50% by weight and 1.25% by weight formic acid,
After immersing at a liquid temperature of 50 ° C. for 300 seconds, it was taken out, washed with water and dried. After that, the sample was left to stand under the conditions shown in Table 1 and subjected to a heat treatment. As a result, the solder wettability measurement results were as shown in Table 1.

(Example 3) The test piece of the test piece was treated with 0.5-wt% of 2- (2-cyclohexylethyl) benzimidazole, 4.0 wt% of formic acid and 0.06 of copper acetate.
After dipping for 160 seconds at a liquid temperature of 40 ° C. in an aqueous solution of wt%, it was taken out, washed with water and dried. After that, the sample was left to stand under the conditions shown in Table 1 and subjected to a heat treatment. As a result, the solder wettability measurement results were as shown in Table 1.

Example 4 The test piece was treated with a surface treatment agent containing 2- (3-cyclohexylbropyr) benzimidazole (0.50% by weight), formic acid (4.5% by weight) and copper acetate (0.0%).
After immersing in a 6 wt% aqueous solution at a liquid temperature of 40 ° C. for 160 seconds, it was taken out, washed with water and dried. After that, the sample was left to stand under the conditions shown in Table 1 and subjected to a heat treatment. As a result, the solder wettability measurement results were as shown in Table 1.

Example 5 A test piece was treated with a surface treatment agent containing 2- (4-cyclohexylbutyl) benzimidazole (0.50% by weight), formic acid (17.5% by weight) and copper acetate (0.0%).
After dipping in a 6 wt% aqueous solution for 12 seconds at a liquid temperature of 40 ° C., it was taken out, washed with water and dried. After that, the sample was left to stand under the conditions shown in Table 1 and subjected to a heat treatment. As a result, the solder wettability measurement results were as shown in Table 1.

Example 6 A test piece was treated with a surface treatment agent of 0.20% by weight of 2- (5-cyclohexylpentyl) benzimidazole, 19.0% by weight of formic acid and 0.1% of copper acetate.
It was immersed in an aqueous solution of 06 wt% at a liquid temperature of 30 ° C. for 16 seconds, taken out, washed with water and dried. After that, the sample was left to stand under the conditions shown in Table 1 and subjected to a heat treatment. As a result, the solder wettability measurement results were as shown in Table 1.

Example 7 A test piece was treated with a surface treatment agent of 2- (6-cyclohexylhexyl) benzimidazole 0.30% by weight, hydrochloric acid 3.0% by weight, cupric chloride 0.
It was immersed in an aqueous solution containing 05% by weight and 10.0% by weight of isopropanol at a liquid temperature of 40 ° C. for 45 seconds, taken out, washed with water and dried. Then, the sample was left under the conditions shown in Table 1 and subjected to heat treatment.
It was as shown in.

Example 8 The test piece was treated with a surface treatment agent containing 2- (2-cyclohexylethyl) -5-methylbenzimidazole (0.50% by weight), formic acid (2.5% by weight) and cupric chloride (0.08% by weight). %, An aqueous solution of 40%
After immersing for 180 seconds, the product was taken out, washed with water and dried. After that, the sample was left to stand under the conditions shown in Table 1 and subjected to a heat treatment. As a result, the solder wettability measurement results were as shown in Table 1.

(Example 9) The test piece was treated with the surface treatment agent of 2- (dichlorohexylmethyl) -5,6-dimethylbenzimidazole (0.50% by weight), acetic acid (4.0% by weight) and cupric bromide (0.1% by weight). Aqueous solution consisting of 03% by weight, liquid temperature 50
After dipping at 360 ° C. for 360 seconds, it was taken out, washed with water and dried.
After that, the sample was left to stand under the conditions shown in Table 1 and subjected to a heat treatment. As a result, the solder wettability measurement results were as shown in Table 1.

(Example 10) The test piece was treated with a surface treatment agent containing 0.50% by weight of 2-cyclohexyl-5-chlorobenzimidazole, 4.0% by weight of acetic acid and 0.0% of zinc chloride.
After dipping in a 4 wt% aqueous solution at a liquid temperature of 50 ° C. for 420 seconds, it was taken out, washed with water and dried. After that, the sample was left to stand under the conditions shown in Table 1 and subjected to a heat treatment. As a result, the solder wettability measurement results were as shown in Table 1.

(Comparative Example 1) A test piece containing 1.0% by weight of 2-undecylimidazole as a surface treatment agent and 1.
After dipping in a 6 wt% aqueous solution at a liquid temperature of 50 ° C. for 25 seconds, it was taken out, washed with water and dried. After that, the sample was left to stand under the conditions shown in Table 1 and subjected to a heat treatment. As a result, the solder wettability measurement results were as shown in Table 1.

Comparative Example 2 A test piece was immersed in an aqueous solution containing 0.35% by weight of 2-pentylbenzimidazole, 1.0% by weight of acetic acid and 0.05% by weight of copper acetate at a liquid temperature of 50 ° C. After soaking for 20 seconds, take out and wash with water,
Dried. After that, the sample was left to stand under the conditions shown in Table 1 and subjected to a heat treatment. As a result, the solder wettability measurement results were as shown in Table 1.

[0042]

[Table 1]

(Embodiment 11) A test piece of a brass plate was degreased, soft-etched, washed with water, immersed in the same treatment agent as in Example 3 under the same conditions, washed with water and dried to obtain a thickness of 0.2.
A conversion film of 0 μm was formed.

[0044]

Effects of the Invention By immersing copper or a copper alloy in an aqueous solution containing a 2- (cyclohexylalkyl) benzimidazole compound as a main component, the surface of the chemical conversion coating film has excellent long-term storage stability and excellent heat resistance. Therefore, the solderability in the surface mounting method of the printed wiring board can be improved.

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[Procedure amendment]

[Submission date] August 6, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

As a method for forming a chemical conversion coating film of a benzimidazole compound on the surface of copper or copper alloy,
A treatment method using 5-methylbenzimidazole is disclosed in JP-A-58-501281, and a treatment method using 2-alkylbenzimidazoles is disclosed in JP-A-4-72072 and 4-80375.
And 4-99285. Besides, 2-
A method for preventing rust of copper or copper alloy using mercaptobenzimidazole is disclosed in JP-A-55-83157, JP-A-62-77600 and JP-A-63-63600.
-118598 publication.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

The 2- (cyclohexylalkyl) benzimidazole compounds suitable for carrying out the method of the present invention include:
2-cyclohexylbenzimidazole, 2- (cyclohexylmethyl) benzimidazole, 2- (2-cyclohexylethyl) benzimidazole, 2- (3-cyclohexylpropyl) benzimidazole, 2- (4
-Cyclohexylbutyl) benzimidazole, 2-
(5-cyclohexylbenzyl) benzimidazole,
2- (6-cyclohexylhexyl) benzimidazole, 2-cyclohexyl-5-methylbenzimidazole, 2- (cyclohexylmethyl) -5-methylbenzimidazole, 2- (2-cyclohexylethyl) -5
-Methylbenzimidazole, 2- (3-cyclohexylpropyl) -5-methylbenzimidazole, 2-
(4-Cyclohexylbutyl) -5-methylbenzimidazole, 2- (5-cyclohexylpentyl) -5-
Methylbenzimidazole, 2- (6-cyclohexylhexyl) -5-methylbenzimidazole, 2-cyclohexyl-5,6-dimethylbenzimidazole, 2
-(Cyclohexylmethyl) -5,6-dimethylbenzimidazole, 2- (2-cyclohexylethyl)-
5,6-Dimethylbenzimidazole, 2- (3-cyclohexylpropyl) -5,6-dimethylbenzimidazole, 2- (4-cyclohexylbutyl) -5,6-
Dimethylbenzimidazole, 2- (5-cyclohexylpentyl) -5,6-dimethylbenzimidazole,
2- (6-cyclohexylhexyl) -5,6-dimethylbenzimidazole, 2-cyclohexyl-5-chlorobenzimidazole, 2- (cyclohexylmethyl)
-5-chlorobenzimidazole, 2- (cyclohexylethyl) -5-chlorobenzimidazole, 2- (3
- cyclohexylpropyl) -5-chloro-benzimidazole, 2- (4 - cyclo hexyl-butyl) -5-chloro-benzimidazole, 2- (5 - cyclo hexyl pentyl) -5-chloro-benzimidazole, 2- (6 - Shi <br/> black hexyl hexyl) and the like 5-chloro-benzimidazole, these 2- (cyclohexyl-alkyl) benzimidazole compound can be synthesized by a known method.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0037

[Correction method] Change

[Correction content]

[0037] (Example 9) Test pieces of the surface treatment agent is 2- (cyclo-hexyl methyl) -5,6-dimethyl benzimidazole 0.50 wt%, acetic acid 4.0 weight% and cupric bromide 0 Aqueous solution consisting of 0.03% by weight, liquid temperature 50
After dipping at 360 ° C. for 360 seconds, it was taken out, washed with water and dried.
After that, the sample was left to stand under the conditions shown in Table 1 and subjected to a heat treatment. As a result, the solder wettability measurement results were as shown in Table 1.

Claims (1)

[Claims] 1. A surface treatment agent for copper and copper alloys, which contains a 2- (cyclohexylalkyl) benzimidazole compound represented by Chemical formula 1 as an active ingredient. [Chemical 1] (However, in the formula, n is an integer from 0 to 6, and R ₁ and R ₂ are the same or different and represent a hydrogen atom, a lower alkyl group or a halogen atom.)