JPH10245684A - Surface treating agent for copper and copper alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a surface treating agent suitable for preflux treatment in a copper circuit part of a printed circuit board by incorporating iodine ion of specified concn. into 2-(arlylmethyl)benzimidazole compd. SOLUTION: The 2-(arylmethyl)benzimidazole compd. is expressed by formula. In the formula, R1 , R2 are hydrogen or halogen atoms, except for both of R1 and R2 are hydrogen. For example, 2-(4-chlorophenylmethyl)benzimidazole is used. This compd. is compounded by 0.01 to 10wt.% in a surface treating agent. Since the compd. is hardly soluble, it may be changed into a soln. by using an org. acid and the like. As for the compd. to be used to supply iodine ion, potassium iodide is used. The concn. of the iodine ion in the surface treating agent is controlled to 10 to 150ppm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[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, JP-B-48-11454, and JP-B-48-2.
Nos. 5621, 49-1983, 49-26183, 58-22545,
No. 61-41988 and JP-A-61-90492. Further, a method of forming a coating film of a 2-position aryl group-substituted imidazole compound on the surface of copper or a copper alloy is described in JP-A Nos. 4-202780 and 4-206681.

Other methods for forming a chemical conversion coating of a benzimidazole compound on the surface of copper or a copper alloy include:
A treatment method using 5-methylbenzimidazole is disclosed in JP-A-58-501281, which discloses a 2-alkylbenzimidazole compound, a 2-arylbenzimidazole compound,
-Aralkylbenzimidazole compound or a treatment method using a 2-mercaptoalkylbenzimidazole compound is disclosed in JP-A-3-124395, JP-A-3-236478, JP-A-4-7207.
No. 2, No. 4-80375, No. 4-99285, No. 4-157174, No.
4-165083, 4-173983, 4-183874, 4-202780
No. 4-206681, No. 4-218679, No. 5-25407, No. 5-
No. 93280, No. 5-93281, No. 5-156475, No. 5-135585
No. 5-156543, 5-186880, 5-186888, 5-
202492, 5-230674, 5-237688, 5-263275
Nos. 5-287562, 5-91729, 5-87563, and
It is described in JP-A-5-291729.

In addition to these, rust prevention methods for copper or copper alloys using 2-mercaptobenzimidazole are disclosed in JP-A-55-83157, JP-A-62-77600 and JP-A-63-118598. . JP-A-4-165083 and JP-A-4-173983 disclose a treatment solution with a sulfate radical brought in from a pretreatment step by allowing a halogen ion such as chlorine or bromine to be present in such an aqueous surface treatment agent. A method for stabilizing the film-forming property against the contamination of copper is disclosed. Japanese Patent Application Laid-Open No. 6-2176 discloses a surface treatment of copper and copper alloy containing 2-undecylimidazole, n-laurylamine and the like. It is described that solderability can be improved by adding a compound containing bromine or iodine to the agent.

[0005]

Recently, as a method of surface mounting a printed wiring board, a processing method with an increased mounting density has become widespread. Such surface mounting methods are classified into two-sided surface mounting in which chip components are joined by cream solder, mixed mounting in which surface mounting of chip components by cream solder and through-hole mounting of discrete components are combined, and the like. In any of the mounting methods, the printed board is soldered a plurality of times and receives a plurality of thermal histories.
Therefore, a chemical conversion coating for protecting a copper circuit of a printed circuit board from air oxidation is required to have good solderability after being subjected to a plurality of thermal histories.

When a printed wiring board is subjected to surface treatment using a conventionally known 2-position long-chain alkylimidazole compound, the surface-treated copper surface is discolored when exposed to a high temperature, and it is difficult to perform subsequent soldering. There was a risk of causing trouble. According to the surface treatment method using a benzimidazole-based compound described in JP-A-3-124395, etc., a conversion coating with relatively excellent heat resistance can be obtained, but in a surface mounting method receiving a plurality of thermal histories, Is not yet in a satisfactory state. In addition, there is still a problem to be solved in the practical application of a surface treating agent to which the compound generating a halogen ion is added.

That is, according to the knowledge of the present inventors, a copper surface treatment agent obtained by adding a compound that generates a halogen ion to a benzimidazole compound can be obtained by adding a chloride ion, a bromine ion, an iodine ion and the like. The heat resistance of the conversion coating formed on the copper surface is improved. This effect is greatest for iodine ions, followed by bromine ions and chlorine ions. However, when these ions are added, the formation rate of the chemical conversion film on the copper surface tends to decrease, and the degree does not appear so much in the case of bromine ions and chloride ions. The rate of film formation is significantly reduced, and 0.1 μm is required to protect copper circuits.
The processing time required to obtain a film thickness of about 0.3 .mu.m was extremely long, and the productivity of the factory was reduced, so that the film could not be put to practical use.

[0008]

SUMMARY OF THE INVENTION Based on such circumstances, the present inventors have improved the heat resistance of a surface treatment agent using a benzimidazole-based compound which forms a chemical conversion film on the surface of copper or a copper alloy. As a result of intensive studies on compounds that do not reduce the film formation rate on copper metal when a compound that generates iodine ions is added, 2- (arylmethyl) benzimidazole compound shown in Chemical formula 2 When iodine ions are contained in an amount of up to 150 ppm, a surface treatment agent for copper and a copper alloy which is excellent in heat resistance and has a small decrease in the film formation rate with respect to copper and is excellent in productivity has been found and completed the present invention. I came to.

[0009]

Embedded image In the formula, R ₁ and R ₂ are a hydrogen atom or a halogen atom, and a compound in which both R ₁ and R ₂ are represented by a hydrogen atom is excluded.

The 2- (arylmethyl) benzimidazole compounds suitable for carrying out the present invention include 2- (4-
Chlorophenylmethyl) benzimidazole, 2- (4
-Bromophenylmethyl) benzimidazole, 2-
(3,4-dichlorophenylmethyl) benzimidazole, 2- (2,4-dichlorophenylmethyl) benzimidazole, 2- (2-chlorophenylmethyl) benzimidazole and the like. 01 to 10% by weight, preferably 0.05 to 5%
It is blended as a percentage by weight.

In practicing the present invention, the 2- (arylmethyl) benzimidazole compound is hardly soluble, so that it is converted into an aqueous solution using an organic acid or an inorganic acid.
An organic solvent miscible with water may be used together with an organic acid or an inorganic acid to form an aqueous solution.

In the practice of the present invention, compounds used to supply iodide ions include potassium iodide, sodium iodide, ammonium iodide, copper iodide, barium iodide, calcium iodide, and iodic acid. Potassium iodide, iodoacetic acid, 2-iodopropionic acid, 3-iodopropionic acid, 2-iodobutyric acid, 3-iodobutyric acid, 4-iodobutyric acid, and the like. May be adjusted to be 10 to 150 ppm.

The organic acids used at this time include formic acid, acetic acid, propionic acid, butyric acid, heptanoic acid, caprylic acid, capric acid, lauric acid, glycolic acid, lactic acid, acrylic acid, benzoic acid, paranitrobenzoic acid, paranitrobenzoic acid and paranitrobenzoic acid. Examples thereof include toluenesulfonic acid, salicylic acid, picric acid, oxalic acid, succinic acid, maleic acid, fumaric acid, tartaric acid, and adipic acid, and inorganic acids include hydrochloric acid, phosphoric acid, sulfuric acid, and nitric acid. These acids are used in an amount of 0.01 to 40 with respect to the aqueous solution.
%, Preferably 0.2 to 20% by weight.

The organic solvent used here is a solvent which can be mixed with lower alcohols such as methanol, ethanol and isopropyl alcohol, and water such as acetone and N, N-dimethylformamide.

The conditions for treating the surface of copper or copper alloy with the surface treating agent of the present invention are as follows.
The contact may be performed at a liquid temperature of 1 ° C for 1 second to 3 minutes. The method of the contact treatment is immersion, spraying, coating or the like.

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

Representative copper compounds usable in the present invention include cuprous chloride, cupric chloride, copper hydroxide, copper phosphate, copper acetate, copper sulfate, copper nitrate, copper bromide and the like. There are also typical zinc compounds such as zinc oxide, zinc formate, zinc acetate, zinc oxalate, zinc lactate, zinc citrate, zinc sulfate, zinc nitrate, zinc phosphate, etc. At a rate of 0.01 to 10% by weight, preferably at a rate of 0.02 to 5% by weight.

As described above, when a copper compound or a zinc compound is used, the pH of a solution can be stabilized by adding a substance having a buffering action such as ammonia or amines in addition to an organic acid or an inorganic acid. desirable. When the surface treating agent of the present invention is used, a double structure of a thermoplastic resin can be formed on the chemical conversion film to improve heat resistance.

That is, 2- or 2-
After forming a chemical conversion film of (arylmethyl) benzimidazole compound, rosin derivative such as rosin, rosin ester, terpene resin derivative such as terpene resin, terpene phenol resin or aromatic hydrocarbon resin, aliphatic hydrocarbon resin, alicyclic ring A hydrocarbon resin such as an aromatic hydrocarbon resin or a thermoplastic resin having excellent heat resistance comprising a mixture thereof is dissolved in a solvent such as toluene, ethyl acetate, or IPA, and a film having a thickness of 1 is formed on the chemical conversion film by a roll coater method or the like. ~ 30
What is necessary is just to apply | coat uniformly so that it may become a micrometer thickness, and just to form a two-layer structure of a chemical conversion film and a thermoplastic resin.

A copper plate or a copper alloy plate surface-treated with a 2- (arylmethyl) benzimidazole compound and a surface treatment agent containing 10 to 150 ppm of iodine ion as an essential component has a particularly excellent heat resistance. A chemical conversion film having properties is formed, and the film formation speed does not decrease remarkably. However, when the concentration of iodine ions exceeds the above range, the film properties such as the solder wetting time and the spread of the cream solder are improved, but the processing time must be remarkably increased, and the working efficiency is extremely reduced. Also,
If the concentration of iodine ions falls below the above range, the chemical conversion film cannot have sufficient heat resistance.

[0021]

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 subjecting a hard copper-clad laminate, which is actually used as a printed wiring board, to a predetermined size and performing a predetermined immersion treatment using a test piece cut into a predetermined size. After forming a chemical conversion coating on the metal surface, it was immersed in a 0.5% hydrochloric acid aqueous solution to extract a 2- (arylmethyl) benzimidazole compound, and contained in this extract using an ultraviolet spectrophotometer. The concentration of the 2- (arylmethyl) benzimidazole compound was measured and converted to the thickness of a chemical conversion film.

The measurement of solder wettability was performed as follows. First, a copper plate having a size of 5 mm × 50 mm × 0.3 mm was used as a test piece, and the test piece was degreased, soft-etched, and washed with water, and then maintained at a predetermined liquid temperature. Each was immersed in a surface treating agent having the following composition for a predetermined period of time, then washed with water and dried to form a chemical conversion film having a thickness of about 0.12 μm on the surface of the test piece.

The test piece subjected to the film formation treatment was left under the conditions shown in Table 1 and was subjected to a heat treatment in a 200 ° C. hot air oven for 10 minutes. Next, a post flux (trade name: JS-64MSS, manufactured by Koki Co., Ltd.) was immersed and attached to the test piece, and the solder wetting time was measured. For the measurement, a solder wettability tester (product name: WET-300)
0, manufactured by Resca Co., Ltd.), 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.

The cream solder spreadability test was performed as follows. As a test piece, a comb-shaped electrode I type used in an insulation resistance test [JIS Z-319]
76.8], the test piece was degreased, soft-etched, and washed with water, then immersed in a surface treatment agent in the same manner as in the measurement of the solder wettability, washed with water, dried, and appropriately applied to the surface of the test piece. After forming chemical conversion coatings of various thicknesses,
Heat treatment was performed in an oven at 00 ° C. for 5 minutes.

Next, a cream solder (trade name: AE-53 HGI, manufactured by Shikoku Kasei Kogyo Co., Ltd.) was printed on the test piece by a single character with a printing width of 3 mm, and an infrared reflow device (product name: MULTI-PRO-306; Reflow heating (peak temperature: 230 ° C.) was performed using the same method as that performed by Toronix Corporation, and the spread length of the spread solder was measured.

Example 1 A treatment aqueous solution having a pH of 3.6 and containing 0.25% by weight of 2- (4-chlorophenylmethyl) benzimidazole, 6% by weight of formic acid and 0.064% by weight of copper acetate was prepared. Further, the iodine ion concentration is 5,
Potassium iodide was dissolved at 10, 20, 50, 100, 150, 200, 300 and 400 ppm to prepare a surface treatment agent. The processing time required for the chemical conversion film formed on the test piece to have a thickness of 0.12 μm using these surface treatment agents, the solder wetting time of the processed test piece, and the spread length of the cream solder Was measured. The results are as shown in Table 1. When the iodine ion concentration is 10 to 150 ppm, the processing time is within 1 minute and the productivity is excellent, and the solder wetting time and the spread properties of the cream solder are excellent. Was also found to be excellent.

[0027]

[Table 1]

Example 2 pH comprising 0.15% by weight of 2- (3,4-dichlorophenylmethyl) benzimidazole, 20% by weight of acetic acid and 0.047% by weight of copper acetate
A treatment aqueous solution of 3.9 was prepared, and the iodine ion concentration of the treatment aqueous solution was set to 5, 10 and 2 in the same manner as in Example 1.
0, 50, 100, 150, 200, 300 and 400
A surface treating agent was prepared by dissolving potassium iodide so as to be ppm. The processing time required for the chemical conversion film formed on the test piece to have a thickness of 0.12 μm using these surface treatment agents, the solder wetting time of the processed test piece, and the spread length of the cream solder Was measured. The measurement results are as shown in Table 2. When the iodine ion concentration is 10 to 150 ppm, the processing time is within 1 minute and the productivity is excellent, and the solder wetting time and the spreadability of the cream solder are improved. It turned out that physical properties were also excellent.

[0029]

[Table 2]

Example 3 0.20% by weight of 2- (2,4-dichlorophenylmethyl) benzimidazole, 10% by weight of acetic acid, 5% by weight of formic acid and 0.047% by weight of copper acetate
, A treatment aqueous solution having a pH of 3.4 was prepared. further,
Iodine ion concentration of 5, 10, 20, 50, 100, 1
Surface treatment agents in which ammonium iodide was dissolved so as to be 50, 200, 300 and 400 ppm were prepared.
The processing time required until the film thickness of the chemical conversion film formed on the test piece using these surface treatment agents becomes 0.15 μm,
In addition, the solder wetting time of the treated test piece and the spread length of the cream solder were measured. These measurement results are as shown in Table 3, and the iodine ion concentration was 10 to 1
In the case of 50 ppm, it was found that the processing time was 1 minute or less and the productivity was excellent, and the solder wetting time and the film properties of the spreadability of the cream solder were also excellent.

[0031]

[Table 3]

Example 4 A treatment aqueous solution having a pH of 3.5 and comprising 0.50% by weight of 2- (2-chlorophenylmethyl) benzimidazole, 8% by weight of formic acid and 0.055% by weight of copper acetate was prepared. Further, the iodine ion concentration is 5,
Sodium iodide was dissolved at 10, 20, 50, 100, 150, 200, 300 and 400 ppm to prepare a surface treatment agent. The processing time required for the chemical conversion film formed on the test piece to have a thickness of 0.15 μm using these surface treatment agents, the solder wetting time of the processed test piece, and the spread length of the cream solder Was measured. These measurement results are as shown in Table 4,
When the iodine ion concentration was 10 to 150 ppm, it was found that the processing time was within 1 minute and the productivity was excellent, and the solder wetting time and the film properties of cream solder spread were also excellent.

[0033]

[Table 4]

Comparative Example 1 0.4% by weight of 2- (5-phenylpentyl) benzimidazole, 8% by weight of acetic acid
And a treatment aqueous solution having a pH of 3.6 consisting of 0.047% by weight of copper acetate and having an iodide ion concentration of 5, 10, 20, 50, 100, 150, 2 in the same manner as in Example 1.
Potassium iodide was dissolved so as to be 00, 300 and 400 ppm to prepare a surface treatment agent. The processing time required for the chemical conversion film formed on the test piece to have a thickness of 0.12 μm using these surface treatment agents, the solder wetting time of the processed test piece, and the spread length of the cream solder Was measured. The results of these measurements are as shown in Table 5, and unlike the above examples, the addition of iodine ions caused a decrease in the film-forming properties, and the effect of improving the properties of the films was small and could not be all satisfied. Was.

[0035]

[Table 5]

Comparative Example 2 1.0% by weight of 2-benzylbenzimidazole, 4% by weight of formic acid and 0.094% of copper acetate
A treatment aqueous solution consisting of 3.5% by weight and having a pH of 3.5 was prepared, and the iodine ion concentration of the treatment aqueous solution was 5, 10, 20, 50, 100, 150, 20 in the same manner as in Example 1.
Potassium iodide was dissolved at 0, 300, and 400 ppm to prepare a surface treatment agent. Using these surface treatment agents, the chemical conversion film formed on the test piece has a thickness of 0.
The processing time required to reach 12 μm, the solder wetting time of the treated test piece, and the spread length of the cream solder were measured. The results of these measurements are as shown in Table 6, and the processing time was significantly prolonged, and the effect of improving the film physical properties was small, and results satisfying all were not obtained.

[0037]

[Table 6]

Comparative Example 3 In Example 1, potassium iodide was replaced with potassium bromide, and the aqueous broth ion concentration was changed to 5, 10, 20, 50, 100, 150, 2 in the treated aqueous solution.
The surface treatment agents of 00, 300 and 400 ppm were prepared. The processing time required for the chemical conversion film formed on the test piece to have a thickness of 0.12 μm using these surface treatment agents, the solder wetting time of the processed test piece, and the spread length of the cream solder Was measured. The results of these measurements are shown in Table 7. The bromine ion has a small effect of improving the film physical properties, especially the spreadability of the cream solder, instead of a small decrease in the film forming property. It was found that the above items were satisfactory.

[0039]

[Table 7]

[Comparative Example 4] In Example 1, potassium iodide was replaced with potassium chloride, and the aqueous chloride solution had a chloride ion concentration of 5, 10, 20, 50, 100, 150, 2
The surface treatment agents of 00, 300 and 400 ppm were prepared. The processing time required for the chemical conversion film formed on the test piece to have a thickness of 0.12 μm using these surface treatment agents, the solder wetting time of the processed test piece, and the spread length of the cream solder Was measured. These measurement results are as shown in Table 7. The chlorine ion has the smallest effect of improving the film properties such as the spreadability of the cream solder although the decrease of the film forming property is the smallest. It was found that the surface treatment agent was satisfactory in all items.

[0041]

[Table 8]

[0042]

The surface treating agent of the present invention has a specific 2-
(Arylmethyl) benzimidazole compound is used as a film-forming component, and an iodine compound is added to the aqueous solution in a range where the concentration of iodine ion is a predetermined amount, so that film properties such as solder wetting time and spread of cream solder are unique. Practical effects such as excellent productivity and good productivity in the processing line of the printed wiring board.

Claims (1)

[Claims] 1. 2- (arylmethyl) represented by the following chemical formula 1.
A copper and copper alloy surface treating agent comprising an aqueous solution containing a benzimidazole compound and 10 to 150 ppm of iodine ions as essential components. Embedded image In the formula, R ₁ and R ₂ are a hydrogen atom or a halogen atom, and a compound in which both R ₁ and R ₂ are represented by a hydrogen atom is excluded.