JPH07243068A - Electrolytic treatment of metal surface - Google Patents

Abstract

PURPOSE:To form a corrosion preventive chemical coating film excellent in moisture, heat and chemical resistances on a metal surface and to improve solderability by electrolyzing the metal surface in an aq. soln. contg.. an imidazole compd. represented by a specified general formula. CONSTITUTION:The metal surface of a printed circuit board, etc., is electrolyzed as the cathode or anode by a PR method, an AC method, a DC method, an AC-DC superposing method or a method using AC in combination in an aq. soln. contg. an imidazole compd. represented by one of formulae I-V, an org. acid and a metallic compd. or further contg. halogenated arom. carboxylic acid. In the formulae I-V, R1 is H, alkyl, phenylalkyl or allyl, R2 is alkyl, phenylalkyl or alkylphenyl, R3 is H, sulfonic acid, alkyl, phenyl or halogen, (n) is 0-17 and (x) is 0-1 but R2 in the formula IV is H, sulfonic acid, alkyl, phenyl, phenylalkyl, alkylphenyl or halogen and R2 in the formula V is arylene. A corrosion preventive adhesive chemical coating film based on the imidazole compd. and having chemical and heat resistances is formed on the metal surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal such as copper, copper alloy, solder, electroless solder, zinc, nickel, gold and silver, and an alloy thereof, such as rust-prevention, solder roughening prevention and discoloration prevention, The present invention relates to a treatment method for improving potency resistance, moisture resistance, chemical resistance, heat resistance, and solderability, and particularly for maintaining the solderability of these metals in a good state for a long period of time and manufacturing printed wiring boards. It is intended to provide a method suitable for preventing surface roughness due to an alkaline solution at the time. Also, since both dissimilar metals joined can be treated, it is ideal for rust prevention of plating pinholes and is suitable as a rustproofing for electroless solder pinholes and as a sealing agent after nickel / gold plating of connectors. It is a thing. It is also suitable as a printed wiring board for connection of chips and packages of high-density surface mounting electronic components. Further, it is suitable for producing a solder through heat treatment of solder powder and a copper through hole printed wiring board treated with an alkaline etching solution.

[0002]

2. Description of the Related Art A method of manufacturing a printed wiring board by a pattern plating method is to make a hole in a copper clad laminate, chemically copper plating, electrolytic copper plating, and then an alkali development type photosensitive film soluble in an alkaline aqueous solution. Form a negative circuit on top,
Then, after electrolytic copper plating and solder plating, the film is brought into contact with an alkaline aqueous solution to remove the alkali developing type photosensitive film.
At this time, the surface of the solder may be attacked by the alkali and the copper material may be exposed. In this case, the circuit may be cut by etching copper with an alkaline etching solution in a later step. Further, when a solder through-hole substrate is manufactured with the solder plating left, the solderability is poor as it is, and it is necessary to perform a fusing treatment or the like. Electroless soldering, which is one of the solder joining techniques for printed wiring boards, is performed by displacement plating. Therefore, it becomes porous and the copper surface of the material is exposed. In addition, precipitation is a mixture of both lead and tin, which are performed separately. For this reason, copper and tin alloys having poor solderability are likely to be generated, and lead and tin are likely to be oxidized, so that good solderability cannot be maintained for a long period unless fusing after plating. Nickel easily forms a strong oxide film and has poor solderability. Therefore, in printed wiring boards and connectors, nickel is plated with gold to prevent oxidation when solderability is required. Chromate treatment is carried out for rust prevention of gold, silver and zinc, but there is a problem because a harmful hexavalent chromium compound is used. Further, for rust prevention of silver, paraffin or the like is dissolved in a solvent and applied, but there is a problem in using the solvent.

[0003]

In recent years, the surface mounting method has been widely adopted as a method for soldering electronic components to a printed wiring board. Due to this surface mounting method, reflow of low melting point cream solder for temporary fixing of electronic parts, the printed wiring board is exposed to high temperatures frequently, and the heat resistance of the pre-flux used to maintain the solderability of the printed wiring board. Of the low melting point cream solder after the printed wiring board is exposed to a high temperature, the wettability, spreadability and solderability of the low melting point solder paste are required to be excellent in the performance of the preflux. In the manufacturing method of a printed wiring board, the reliability as a solder etching resist film is poor and manufacturing defects are likely to occur.Therefore, when the alkali development type photosensitive film is peeled off, solder roughening during alkali etching is prevented and good circuit formation is achieved. While maintaining good solderability. Further, in the electroless solder, not only thermal stress to the substrate is strong but also costly fusing is not performed, but good solderability is maintained by rust preventive treatment. Nickel does not use expensive gold plating to prevent discoloration and maintain good solderability. Silver,
Zinc is treated with a safe solution containing no harmful hexavalent chromium compound to prevent discoloration for a long period of time and maintain good solderability. Also, the sealing treatment maintains the corrosion resistance of the connector terminals. In the method of manufacturing a printed wiring board, the deviation during cream solder printing, the solder film thickness, the productivity, the cost, etc. are poor. Therefore, it is earnestly desired to develop a solder substrate that is excellent in the uniformity of the solder film thickness and in the control of the film thickness after the reflow treatment after the solder powder is adhered after selectively reacting the adhesive chemical conversion film only on the exposed metal parts. ing.

[0004]

In view of such circumstances, the present inventors have found that the low melting point cream solder has wettability and spreadability even after being exposed to a high temperature. Solderability after reflow,
Heat-resistant water-soluble pre-flux agent with good wettability. Also, peeling of the alkali-developable photosensitive film, solder roughening during alkali etching, solder rust to prevent discoloration, and electroless solder rust prevention. In addition, it is a rust preventive agent with excellent rust prevention, moisture resistance, heat resistance, and solderability for connector parts and nickel substrates.
Also, an adhesive that selectively reacts the adhesive film only on the exposed portion of the metal to attach the metal powder. Further, as a result of repeated intensive studies on the surface protection to resist the alkaline etching solution by forming a chemical conversion film on the copper circuit part, as the organic acid used in the practice of the present invention, acetic acid, iodoacetic acid, bromoacetic acid,
Dimethyl acetic acid, diethyl acetic acid, α-bromoacetic acid, paranitrobenzoic acid, paratoluenesulfonic acid, picric acid,
Organic acids such as oxalic acid, formic acid, succinic acid, maleic acid, acrylic acid, fumaric acid, tartaric acid, adipic acid, lactic acid, oleic acid, citric acid, metasulfonic acid, sulfamic acid, hydrochloric acid, sulfuric acid, phosphorous acid, phosphoric acid, etc. There are inorganic acids, other carboxylic acids, halogenated fatty acids, halogenated aromatic carboxylic acids and the like, which may be added in a proportion of 0.01 to 20% with respect to water. One or more compounds represented by (Chemical formula 1) to (Chemical formula 5) may be added as an active ingredient at a ratio of 0.1 to 5% with respect to the acid aqueous solution. Typical compounds used as metal ions in the practice of the method of the present invention include lithium, beryllium, potassium, magnesium, zinc acetate, zinc formate, zinc lactate, zinc counate, zinc benzoate, zinc oxalate, and water. Zinc oxide, zinc bromide, zinc phosphate, zinc oxide, zinc chloride, lead acetate, lead hydroxide, lead bromide, lead iodide, lead oxalate, lead borate, ferrous chloride, ferric chloride, bromide Cuprous, cupric bromide, cuprous iodide, copper formate, nickel chloride, nickel acetate, cuprous chloride, cupric chloride, cuprous oxide, cupric oxide, copper hydroxide,
It is a metal compound such as copper phosphate, copper carbonate, copper acetate, and copper sulfate, and may be added in a proportion of 0.001 to 5% with respect to water. The halogenated aromatic carboxylic acid used in the practice of the present invention includes 3-bromo-4methylbenzoic acid,
4- (bromomethyl) phenylacetic acid, G-bromophenylacetic acid, α-bromotetradecanoic acid, 2-bromophenylacetic acid, 3-bromophenylacetic acid, 4-bromophenylacetic acid, etc., and 0.01 to 20 with respect to the aqueous solution. %, Preferably 0.1 to 5%.
Examples of the halogenated fatty acid used in the practice of the present invention include bromoacetic acid and 3-bromo-2- (bromomethyl).
Propionic acid, 2-bromobutanoic acid, 4-bromobutanoic acid, 2-bromohexanedecanoic acid, 2-bromohexanoic acid, 2-bromo-3-methylbutanoic acid, 2-bromo2-
Methylpropionic acid, 2-bromooctanoic acid, 8-bromooctanoic acid, 2-bromopropionic acid, 3-bromopropionic acid, 2-bromopentanoic acid, 5-bromopentanoic acid, chloroacetic acid, chlorobutyric acid, chloropropionic acid, etc. Therefore, it may be added in the range of 0.01 to 20%, preferably 0.1 to 5% with respect to the aqueous solution. In the practice of the present invention, when it becomes difficult to dissolve the compound represented by (Chemical formula 1) to (Chemical formula 5) and the organic acid, the metal compound, the halogenated aromatic carboxylic acid, or the halogenated fatty acid, methanol or ethanol is used. Water-soluble solvents such as isopropyl alcohol, butanol, and acetone can be used alone, or can be mixed and used at an arbitrary ratio. For example, the above water-soluble solvent may be used alone or in combination with other organic acids, etc. In particular, when the organic acid alone is used, it is difficult to dissolve the compound represented by (Chemical formula 1) to (Chemical formula 5) or its derivative. In this case, it is preferable to add a water-soluble solvent, and the content ratio in this case is 0.01 to
In many cases, 60% is appropriate. It is also effective to add a surfactant and an emulsifying dispersant. One or two of the compounds represented by (Chemical formula 1) to (Chemical formula 5) and the organic acid, the metal compound, etc. used in the method of the present invention are used.
By performing electrolytic treatment, ultrasonic wave, and electromagnetic wave treatment in an aqueous solution containing more than one type, a dense rust-proof chemical conversion film, chemical-resistant chemical conversion film, and heat-resistant chemical conversion film can be obtained in a short time, solder wettability,
The solder spreadability can be further enhanced. By the metal surface treatment of the present invention, a rust preventive conversion film, a chemical resistance conversion film,
To apply a heat-resistant chemical conversion coating to a metal surface, an electrolytic treatment is performed while the metal surface is in contact with a treatment liquid. Also,
When ultrasonic waves or electromagnetic waves are irradiated while the metal surface is in contact with the treatment liquid, it effectively penetrates into the inside of the holes. It is suitable that the temperature of the treatment liquid to be brought into contact is in the temperature range of 0 to 100 ° C. and the immersion time is several seconds to several tens of minutes. The electrolytic treatment is
Current density of 0.01 A / dm ² to 10 at cathode or anode
In the A / dm ² range, it is suitable that the immersion time is several seconds to several tens of minutes. Further, as a treatment for further improving the moisture resistance and the chemical resistance after forming the rust preventive conversion film, infrared / near-infrared / far-infrared / ultraviolet irradiation treatment is performed in a temperature range of 0 to 300 ° C.
Treatment time of several seconds to several tens of minutes is effective. The method for synthesizing the compounds represented by (Chemical formula 1) to (Chemical formula 5) used in the practice of the method of the present invention can easily be carried out by removing impurities after the amine and the fatty acid are reacted by heating.
A compound represented by (Chemical Formula 5) can be obtained.

[0005]

According to the above-mentioned treatment method, (Chemical formula 1) to (Chemical formula 5) effective for rust prevention are applied to metal surfaces such as copper, copper alloy, solder, electroless solder, nickel, gold, silver and zinc. A rust preventive conversion film, a chemical resistant conversion film, a heat resistant conversion film, and an adhesive conversion film mainly formed. These chemical conversion coatings are water-repellent and have excellent moisture resistance, heat resistance, and chemical resistance, and protect the metal surface for a long period of time, as well as the wettability and spreadability of low-melting point cream solder, solder rise after reflow, and wettability. It is good. Further, the uniformity of the solder film thickness after the solder powder is adhered to the adhesive chemical conversion film and the reflow treatment is performed is good. Further, a chemical resistant chemical conversion film is formed on a necessary copper circuit portion and then treated with an alkali etching solution, whereby the production of a copper through-hole wiring board is good. In addition, it is possible to manufacture a printed wiring board excellent in terms of work environment and safety. Further, by performing electrolytic treatment, ultrasonic wave, and electromagnetic wave treatment, a dense film can be formed in a short time.

[0006]

EXAMPLES Compounds represented by (Chemical formula 1) to (Chemical formula 5) (Table 1
0.5%), succinic acid, cupric chloride,
An aqueous solution of each type containing ion-exchanged water or the like or an emulsified aqueous solution was prepared, put in a 100 ml container, and the liquid temperature was heated to 40 ° C. for adjustment. On the other hand, on a copper plate of 1 cm x 5 cm x 0.3 mm, copper sulfate plating, electroless copper plating, electric solder plating, electroless solder plating, nickel plating,
It was silver plated. Then, the metal surface is washed, immersed in 0.5% aqueous solution of each type containing the compounds represented by the above (Chemical formula 1) to (Chemical formula 5) as an active ingredient, and 1 A / dm ² at the cathode.
Electrolyzed for 30 seconds and anode 0.5A /
Electrolytic treatment was performed for 30 seconds for dm ² . After that, it is washed with water to prepare a test piece of (1), and then the test piece of (1) is put in a hot air dryer and heated at 200 ° C. for 5 minutes and immersed in post flux before measurement using a solder wettability tester. And the wetting time was measured. (2) After applying the rosin-based preflux to the test piece, put the sample piece in a hot air dryer and heat at 200 ° C. for 5 minutes, immerse it in the boss flux before measurement, and use a solder wettability tester. And the wetting time was measured. Moisture resistance (MIL-STD
-202F-M-106E), the test piece was immersed in post flux and the wetting time was measured using a solder wettability tester. (4) The alkaline solution and the alkaline etching solution were heated to 40 ° C., and the test piece was immersed for 5 minutes. After that, wash with water and check the surface condition (roughness, discoloration). The gas corrosion test (1 ± 0.
The surface condition (roughness, discoloration) of the metal after 3 ppm H ₂ S, 25 ± 2 ° C., 5% RH, 10 days) is observed. (6)
Apply solder powder to the test pieces of ~ and check the adhesiveness and the uniformity of the film after reflow. The test results are shown in Table 1.

[Table 1]

[0007]

According to the treatment method of the present invention, a chemical conversion rust preventive film having excellent moisture resistance, heat resistance and chemical resistance on a metal surface,
Chemical resistance chemical conversion film, heat resistance chemical conversion film, and adhesive chemical conversion film are formed, and it has the effect of good wettability and spreadability of low melting point cream solder, good solderability after reflow, and good wettability. This is particularly effective for surface mounting. In addition, the pattern plating method not only prevents solder roughening during alkaline aqueous solution treatment during printed wiring board manufacturing and eliminates the risk of circuit disconnection, but also leaves solder at the soldering part and has good solderability without fusing treatment. It can be kept in good condition. It is also suitable as a sealing agent after nickel / gold plating of the connector. It is also suitable as a printed wiring board for connection of chips and packages of high-density surface mounting electronic components. Further, it is suitable for producing a solder through heat treatment of solder powder and a copper through hole printed wiring board treated with an alkaline etching solution. In addition, the adhesive chemical conversion coating has excellent rust prevention, heat resistance, good adhesion of solder powder, excellent solder spreadability after reflow, wettability and uniformity, as well as excellent work environment and safety. It is possible to manufacture wiring boards and metal parts.

Claims (7)

[Claims] 1. A metal surface is used as a cathode or an anode in an aqueous solution containing the compounds represented by (Chemical formula 1) to (Chemical formula 5),
A method for rust-preventing metal and surface-treating metal, which comprises electrolyzing by a PR method, an AC method, a DC method, an AC / DC superposition method, and an AC combined method. [Chemical 1] [Chemical 2] [Chemical 3] [Chemical 4] [Chemical 5] 2. A metal surface is used as a cathode or an anode in an aqueous solution containing the compounds represented by (Chemical formula 1) to (Chemical formula 5), an organic acid, a metal compound, etc. A method for rust-preventing metal and surface-treating metal, which comprises electrolyzing by a superposition method and an alternating current combined method. 3. A metal surface is used as a cathode or an anode in an aqueous solution containing compounds represented by (Chemical formula 1) to (Chemical formula 5), an organic acid, and a halogen ion, and a PR method, an AC method, a DC method,
A surface treatment method for a metal, which comprises electrolyzing by an alternating current superposition method and an alternating current combined method. 4. A PR method, an AC method, a DC method, wherein a metal surface is used as a cathode or an anode in an aqueous solution containing a compound represented by (Chemical formula 1) to (Chemical formula 5), an organic acid, a metal compound and a halogen ion. A surface treatment method for a metal, which comprises electrolyzing by an alternating current superposition method and an alternating current combined method. 5. A method of manufacturing a printed wiring board, which comprises performing a soldering treatment after the surface treatment of the metal according to any one of claims 1 to 4. 6. After the surface treatment of the metal according to any one of claims 1 to 4, infrared reflow, near infrared reflow, far infrared reflow, nitrogen reflow, vapor reflow treatment of heating in air or a nitrogen atmosphere is performed. A method for manufacturing a characteristic printed wiring board. 7. A method of manufacturing a printed wiring board, which comprises performing an alkaline solution treatment after the surface treatment of the metal according to any one of claims 1 to 4.