JPH0569914B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for surface treatment of copper and copper alloys, and particularly to a method suitable for rust prevention treatment and formation of etching resist films in circuit areas of printed wiring boards. This is what we provide.

Prior Art Surface treatment methods for forming a film of a 2-position long-chain alkylimidazole compound on the surface of copper or copper alloy are disclosed in Japanese Patent Publications No. 46-17046, No. 48-11454, No. 48
−25621, No. 49-1983, No. 49-26183, No. 58
-22545, 61-41988 and JP-A-61-90492
It is stated in each publication of the issue.

Problems to be Solved by the Invention Recently, surface treatment of copper and copper alloys with a film of such a long-chain alkylimidazole compound has been attracting attention as a method for protecting the circuit portion of a printed wiring board.

However, in conventional surface treatment methods, in order to form a sufficiently thick chemical conversion film, the copper surface must be brought into contact with an aqueous solution of a long-chain alkylimidazole compound at a relatively high temperature for a long period of time.

Therefore, it has not been possible to cope with the high-speed manufacturing process of printed wiring boards, and it has not been possible to appropriately treat the copper surface in small-diameter through holes such as those in copper through-hole printed wiring boards.

Means for Solving the Problems In view of the above circumstances, the inventors of the present invention repeatedly conducted various tests, and found that in forming a film of 2-position long chain alkylimidazole on the surface of copper or copper alloy, We have discovered that by contacting a 2-position long-chain alkylimidazole compound with a treatment solution containing copper ions, a chemical conversion coating with sufficient thickness can be obtained by contact treatment at a lower temperature and in a shorter time than in conventional methods. The invention has been completed.

In carrying out the method of the present invention, when bringing copper or copper alloy into contact with a treatment solution containing a 2-position long chain alkylimidazole compound and copper ions, an acidic substance, preferably an organic acid compound, is added to the treatment solution, Its pH should be adjusted to a range of 3 to 6.

Furthermore, an acidic substance and ammonia or amines should be added to the processing solution to avoid precipitation of a complex formed by the reaction between the imidazole compound and copper ions in the processing solution.

Typical 2-position long chain alkylimidazole compounds used in the present invention include 2-amylimidazole, 2-heptylimidazole,
-decylimidazole, 2-undecylimidazole, 2-dodecylimidazole, 2-tridecylimidazole, 2-tetradecylimidazole, 2-heptadecyl imidazole, 2-undecyl-4-methylimidazole, 2-heptadecyl-4-methylimidazole and salts thereof, and 2-undecyl imidazole, 2-undecyl-4-methylimidazole, and salts thereof are particularly preferred.

Typical substances that generate copper ions in the treatment solution include copper powder, cuprous chloride, cupric chloride, copper hydroxide, copper phosphate, copper acetate, copper sulfate, copper nitrate, copper bromide, etc. Of these, cuprous chloride is particularly preferred.

2-position long chain alkylimidazoles are poorly soluble in water, so to dissolve them in water,
A water-soluble salt may be obtained by using a mixed solvent of water and an organic solvent, or by reacting a long-chain alkylimidazole with an organic or inorganic acid.

Examples of organic solvents used in this case include methanol, ethanol, propanol, ethylene glycol, propylene glycol, cellosolves, acetone, and acetonitrile.

The organic acids or inorganic acids used to make the 2-position long chain alkylimidazole into a water-soluble salt include benzoic acid, acetic acid, formic acid, lactic acid, propionic acid, stearic acid, palmitic acid, lauric acid,
These include caprylic acid, caproic acid, glycolic acid, succinic acid, maleic acid, tartaric acid, adipic acid, and phosphoric acid.

In the method of the present invention, the amines used to prevent complexes of copper ions and long-chain alkylimidazole from precipitating in the treatment solution include methylamine, dimethylamine, ethylamine, monoethanolamine, diethanolamine, triethanolamine, etc. be.

In carrying out the present invention, ammonia, amines, alkali metal hydroxides (or carbonates), alkaline earth metal hydroxides (or carbonates), etc. are added in advance to a substance that generates copper ions. It is desirable to increase solubility.

The treatment liquid used in the method of the present invention has a pH of 3 to 3.
It should be adjusted to be in the range of 6, preferably in the range of 4 to 5. If the pH of the treatment solution containing long-chain alkylimidazole compounds and copper ions is too high,
A complex of long-chain alkylimidazole and copper ions becomes insolubilized and precipitates in the solution. On the other hand, if the PHH is too low, it is difficult for the long-chain alkylimidazole to form a complex with the copper ions on the metal surface, resulting in an extremely low rate of formation of the chemical conversion film.

The processing liquid used in the method of the present invention includes solution 1
5 to 5 long-chain alkylimidazole compounds per
50 g, and a substance that generates copper ions may be added at a ratio of 0.1 to 5 g.

To carry out the method of the present invention, the surface of the copper or copper alloy is mechanically polished or acid-washed, and then the metal is freshly immersed in a treatment solution, or the treatment solution is applied or sprayed onto the metal surface. Good.

In the method of the present invention, the surface of copper or copper alloy is immersed in a treatment solution at a temperature of approximately 25°C to 40°C.
0.1μ~ by contacting for 20 seconds to 20 seconds.
A conversion coating of 1.2μ can be formed, and if a larger conversion coating is required, the treatment temperature may be higher or the contact time may be longer.

Effect The long-chain alkylimidazole compound at the 2-position dissolves well in an acidic aqueous solution, and most of the dissolved long-chain alkylimidazole compound at the 2-position is quaternized in the solution. When a solution containing this 2-position long-chain alkylimidazole compound is brought into contact with copper or a copper alloy in the presence of oxygen, the copper is oxidized and copper ions are eluted to form a complex with imidazole. There are two possible complexes formed at this time: a complex containing copper ions, imidazole, and organic acid ions or inorganic acid ions, and a complex consisting only of water-insoluble copper and imidazole. Among these complexes, it is thought that a water-insoluble copper imidazole complex is deposited on the copper plate to form a film.

In the above reaction, the rate at which copper is oxidized and ionized in the solution containing the 2-position long-chain alkylimidazole compound is considered to be the rate-limiting factor for film formation. At this time, by making copper ions exist in the solution in advance, a complex consisting of copper ions, imidazole, and organic acid ions is already present. In the presence of oxygen in this state, the complex further reacts with copper to form an insoluble copper imidazole complex and copper acetate. The insoluble copper imidazole complex formed at this time forms a film on the surface of the copper or copper alloy, and the copper acetate is again used to form a complex consisting of copper ions, imidazole, and acetic acid.

In this way, the imidazole organic acid solution in which copper ions are pre-existing does not require the initial elution of copper ions, which is thought to take the longest time for the reaction, so copper ions can be removed from the solution after the reaction has progressed. Since the copper ions form a complex with imidazole and organic acid ions, the reaction system described above is repeated, resulting in an accelerated precipitation rate of the complex and the formation of a complex on the surface of the copper or copper alloy. It seems that a film can be formed quickly.

EXAMPLES The present invention will be specifically explained below with reference to Examples and Comparative Examples.

In addition, in these tests, the thickness of the chemical conversion coating on the metal surface was determined by measuring 0.5
% hydrochloric acid aqueous solution to elute the long-chain alkylimidazole, measure the concentration of the long-chain alkylimidazole contained in this solution using an ultraviolet spectrophotometer, and calculate the concentration of the chemical conversion coating based on the following empirical formula. This is the calculated thickness.

Film thickness (μ) = 0.253×A×y/S [where A is the maximum absorbance at 210 to 220 mμ, S is the surface area of the test piece (cm ² ), and y is the amount of the hydrochloric acid aqueous solution used (ml). ] Example 1 2-andecyl-4-methylimidazole 10g
was added to 20 ml of acetic acid and mixed uniformly. On the other hand, 0.4 g of cuprous chloride was added to 6 ml of 25% ammonia water and stirred well. Both solutions were added to 1 part of water, stirred well, and the pH was adjusted to 4.40. A clear processing solution was prepared.

Next, the copper surface of the copper-clad laminate was polished using a wet polishing material (product name: Scotchibrite, manufactured by Sumitomo 3M), immersed in a 1% hydrochloric acid aqueous solution for 30 seconds, thoroughly rinsed with water, dried, and tested. It was a piece. When this test piece was immersed in the treatment liquid for 10 seconds at a liquid temperature of 30°C, washed with water and dried, the chemical conversion coating on the test piece was 0.3μ. This test piece was heated to 55°C.
It was left in a constant temperature and humidity chamber with a humidity of 95% for 500 hours, but
No corrosion was observed on the copper surface.

Next, a post flux (product name: "Soldox FR207" manufactured by Totsupifu Asner Co., Ltd.) was applied to the test piece made of this copper-clad laminate, and it was immersed in a solder bath at 255°C for 2 seconds, but the solder on the copper surface did not wet. The condition was good.

Comparative example 1 2-undecyl-4-methylimidazole 10g
and 4.5 ml of acetic acid were respectively added to 1 part of water and stirred well to prepare a treatment solution with a pH of 4.70. Using this treatment solution, the treatment was carried out under the same conditions as in the previous example.
The thickness of the chemical conversion film on the surface of the test piece was 0.1μ.

When this test piece was left in a constant temperature and humidity chamber at a temperature of 55°C and a humidity of 95% for 500 hours, spotty rust appeared locally on the test piece.

Example 2 10 g of 2-undecylimidazole was added to 20 ml of propionic acid and mixed uniformly, and on the other hand cuprous chloride
Add 0.4 g and 1.2 g of triethanolamine to 5 ml of 25% ammonia water, stir well, and dilute both solutions with 1 ml of water.
A clear treatment solution with a pH of 4.45 was prepared by adding each to the solution and stirring well.

Next, a test piece made of a copper-clad laminate treated in the same manner as in Example 1 was immersed in the treatment solution at a temperature of 30°C for 10 seconds, washed with water, and dried. The chemical conversion coating on the test piece was 0.35μ. This was left in a constant temperature and humidity chamber at a temperature of 55°C and a humidity of 95% for 500 hours, but no corrosion was observed on the copper surface. Further, the wettability of solder on the copper surface was examined in the same manner as in Example 1, and the results were also good.

For comparison, 2-undecylimidazole
Add 10 g of propionic acid and propionic acid to 1 part of water and stir well to prepare a treatment solution with a pH of 4.45. Using this treatment solution, the same test piece as above was immersed for 10 seconds at a solution temperature of 30 ° C. When washed with water and dried, the chemical conversion coating on the test piece was found to be 0.05μ, and when the same moisture resistance test as above was performed, rust was found to be partially generated on the surface of the test piece.

Example 3 2-undecyl-4-methylimidazole 10g
and 2.0 g of cuprous chloride in 100 ml of ethanol to completely dissolve the cuprous chloride. Add 7.7 ml of acetic acid and 300 ml of water to this solution, stir well, and make a clear solution with a pH of 4.35. A treatment solution was prepared.

Next, a test piece made of a copper-clad laminate treated in the same manner as in Example 1 was immersed in the treatment solution at a temperature of 30°C for 10 seconds, washed with water, and dried. The chemical conversion coating on the test piece was 0.4μ. Yes, this is done at a temperature of 55℃ and humidity.
Although it was left in a constant temperature and humidity chamber at 95% for 500 hours, no corrosion was observed on the copper surface. Further, the wettability of solder on the copper surface was examined in the same manner as in Example 1, and the results were also good.

For comparison, 10 g of 2-undecyl-4-methylimidazole was added to a mixed solvent of 100 ml of ethanol and 300 ml of water, stirred well to dissolve completely, and acetic acid was added to this solution to form a transparent solution with a pH of 4.35. Prepare a treatment solution and add the same test piece as above to this treatment solution at a temperature of 30
After immersing it at ℃ for 10 seconds, washing it with water and drying it, the chemical conversion coating on the test piece was found to be 0.13μ, and when the same moisture resistance test as above was performed, it was found that rust had formed partially on the copper surface of the test piece. It was hot.

Example 4 5 g of 2-undecyl imidazole and 5 g of 2-undecyl-4-methylimidazole were added to 20 ml of glycolic acid and mixed uniformly, and 0.2 g of copper powder was added.
Add to 5 ml of 25% ammonia water and stir well, add both solutions to 1 part of water, stir well, and adjust to pH4.48.
A clear treatment solution was prepared.

Next, a test piece made of a copper-clad laminate treated in the same manner as in Example 1 was immersed in the treatment solution at a temperature of 30°C for 10 seconds, washed with water, and dried. The chemical conversion coating on the test piece was 0.38μ. This was left in a constant temperature and humidity chamber at a temperature of 55°C and a humidity of 95% for 500 hours, but no corrosion was observed on the copper surface. In addition, the wettability of solder on the copper surface was investigated in the same manner as in Example 1.
The results were also good.

For comparison, 2-undecylimidazole 5
g and 2-undecyl-4-methylimidazole 5
g of each were added to 1 part of water, and glycolic acid was added thereto while stirring to prepare a transparent treatment liquid with a pH of 4.48. Using this treatment liquid, the same test piece as above was immersed for 10 seconds at a liquid temperature of 30°C, washed with water, and dried. The chemical conversion coating on the test piece was 0.1μ, and a moisture resistance test was performed in the same manner as above. Upon inspection, some rust appeared on the surface of the test piece.

Example 5 8 g of 2-undecylimidazole and 2 g of 2-heptadecyl imidazole were added to 22.2 ml of acetic acid and mixed uniformly. On the other hand, 1.0 g of cupric chloride was added to 12 ml of 25% aqueous ammonia and stirred well to form both solutions. water 1
and stirred well to prepare a treatment solution with a pH of 4.74.

Next, a test piece made of a copper-clad laminate treated in the same manner as in Example 1 was immersed in the treatment solution at a temperature of 30°C for 10 seconds, washed with water, and dried. The chemical conversion coating on the test piece was 0.3μ. Yes, this is done at a temperature of 55℃ and humidity.
Although it was left in a constant temperature and humidity chamber at 95% for 500 hours, no corrosion was observed on the copper surface. Further, the wettability of solder on the copper surface was examined in the same manner as in Example 1, and the results were also good.

For comparison, 2-undecylimidazole 8
g and 2 g of 2-heptadecyl imidazole in 1 portion of water
Add acetic acid to this while stirring.
A treatment solution with a pH of 4.74 was prepared. Using this treatment liquid, the same test piece as above was immersed for 10 seconds at a liquid temperature of 30°C, then washed with water and dried. The chemical conversion coating on the test piece was 0.05μ, and the same moisture resistance test as above was performed. Upon inspection, some rust was observed on the surface of the test piece.

Example 6 7 g of 2-undecyl-4-methylimidazole
and 2-heptadecyl-4-methylimidazole 3
g to 16.5 ml of formic acid and mixed uniformly. On the other hand, add 0.55 g of cupric chloride to 4.6 ml of 25% ammonia water and stir well. Add both solutions to 1 ml of water, stir well, and adjust the pH to 4. A treatment solution of .74 was prepared.

Next, a test piece made of a copper-clad laminate treated in the same manner as in Example 1 was immersed in the treatment solution at a temperature of 30°C for 10 seconds, washed with water, and dried. The chemical conversion coating on the test piece was 0.28μ. This was left in a constant temperature and humidity chamber at a temperature of 55°C and a humidity of 95% for 500 hours, but no corrosion was observed on the copper surface. In addition, the wettability of solder on the copper surface was investigated in the same manner as in Example 1.
The results were also good.

For comparison, 7 g of 2-undecyl-4-methylimidazole and 3 g of 2-heptadecyl-4-methylimidazole were each added to 1 part of water, and formic acid was added to this with stirring to prepare a treatment solution with a pH of 4.74. The same test piece as above was immersed in a solution at a temperature of 30°C for 10 seconds, washed with water, and dried. The chemical conversion coating on the test piece was 0.08μ. When the same moisture resistance test as above was performed, the test piece was Many spots of rust appeared on the surface.

Example 7 Using the treatment solution prepared in Example 1, a test piece made of a brass plate that had been washed in the same manner as in Example 1 was immersed in the treatment solution at a temperature of 30°C for 10 seconds, then washed with water and dried. However, the chemical conversion coating on the test piece was 0.2μ.
It was hot. These specimens were heated to a temperature of 55℃ and a humidity of 95%.
When left in a constant temperature and humidity chamber for 500 hours, no corrosion was observed on the brass surface.

Example 8 2-undecyl-4-methylimidazole 10g
Add 2.5g of equimolar acetic acid to this and an appropriate amount of water,
Prepare an aqueous solution containing 2-undecyl-4-methylimidazole acetate, and add 0.4 g of copper sulfate to 10 ml of water.
These were each added to water to make a total amount of 1, and triethanolamine was added while stirring to prepare a treatment liquid with a pH of 4.9.

Next, a test piece made of a copper-clad laminate treated in the same manner as in Example 1 was immersed in the treatment solution at a temperature of 30°C for 10 seconds, washed with water, and dried. The chemical conversion coating on the test piece was 0.3μ. Yes, this is done at a temperature of 55℃ and humidity.
Although it was left in a constant temperature and humidity chamber at 95% for 500 hours, no corrosion was observed on the copper surface. Further, the wettability of solder on the copper surface was examined in the same manner as in Example 1, and the results were also good.

Example 9 A small hole was made in a 1.6 m/m thick glass epoxy double-sided copper-clad laminate [FR-4, product name R-1705, (manufactured by Matsushita Electric Works Co., Ltd.]) and electroless copper plating was applied, followed by electrolytic copper plating. Plating was performed to form a copper plating of 25 to 30 μm inside the hole and on both sides.

Next, a resist ink whose main component is an alkali-soluble rosin-modified phenolic resin [product name KM-10]
(manufactured by Taiyo Ink Manufacturing Co., Ltd.)] was silk screen printed to form a negative pattern coating film with a thickness of about 20 μm, and dried at a temperature of 80° C. for 10 minutes.

Further, the substrate was immersed in a 5% aqueous hydrochloric acid solution and washed with water to clean the copper surface, and the substrate was immersed in the treatment solution prepared in Example 1 at a temperature of 50° C. for 60 seconds.

Thereafter, the substrate was taken out, washed with water, and dried at 120°C for 10 minutes. When the thickness of the alkylimidazole film on the substrate was measured, it was 3.5μ on average.

Next, the substrate is immersed in a 2% sodium hydroxide aqueous solution to dissolve and remove the resist ink, exposing the copper in areas (negative areas) that do not need to be left as circuits, and then using an alkaline etching agent [ammonium-ammonium chloride]. - Copper-based, product name process (manufactured by Meltex Co., Ltd.)] and heated at 50°C.
The substrate was etched by spraying for 120 seconds at a temperature of 100 mL, and then immersed in a 5% hydrochloric acid aqueous solution to dissolve and remove the etching resist film on the circuit, producing a copper through-hole printed wiring board.

The defect rate of the copper through-hole printed wiring board thus produced was 1% or less.

For comparison, a treatment solution was prepared by adding 10 g of 2-undecyl-4-methylimidazole and 4.5 ml of acetic acid to 1 part of water, and using this treatment solution, the same copper-clad laminate as above was treated under the same conditions as above. A copper through-hole printed wiring board was manufactured by processing. The average thickness of the alkylimidazole film on the substrate was measured to be 0.8μ, and there were many through-hole defects and circuit defects, and the product defect rate was 70%.

Effects of the Invention When forming an imidazole compound film on the surface of copper or copper alloy by the method of the present invention, the contact time between the metal and the treatment liquid is reduced to at least 1/3 compared to the conventional method. This makes it possible to dramatically improve production efficiency in antirust treatment for circuit parts such as printed wiring boards and in the process of forming etching resist films.

Furthermore, since the treatment can be carried out at low temperatures, equipment can be simplified and energy can be saved.

Claims (1)

[Scope of Claims] 1. A method for surface treatment of copper and copper alloys, which comprises bringing the surface of copper or copper alloys into contact with a treatment solution containing a 2-position long-chain alkylimidazole compound and copper ions. 2. The method for surface treatment of copper and copper alloys according to claim 1, characterized in that an acidic substance is added to the treatment liquid to adjust the pH of the treatment liquid to a range of 3 to 6. 3. The method for surface treatment of copper and copper alloys according to claims 1 and 2, characterized in that an acidic substance and ammonia or amines are added to the treatment liquid. 4. The method for surface treatment of copper and copper alloys according to claims 2 and 3, wherein an organic acid is used as the acidic substance. 5. A method for surface treatment of copper and copper alloys, which comprises bringing copper or copper alloys into contact with a treatment solution containing a 2-undecylimidazole compound, cuprous chloride, an organic acid, and ammonia.