JPH06299375A - Treatment of metallic surface such as solder, electroless solder, ag, ni, zn, cu and cu alloy - Google Patents

Abstract

PURPOSE:To form a chemical conversion film superior in moisture resistance, chemical resistance and heat resistance on a metallic surface, to prevent rust and to enhance a soldering property and a wetting property by bringing the metallic surface into contact with an aqueous solution of a specific imidazole derivative. CONSTITUTION:A metallic surface such as solder, electroless solder, Ag, Ni, Zn, Cu, and Cu alloy is brought into contact with an aqueous solution incorporating a compound represented with a formula, (in the formula, R1: hydrogen, alkyl group, phynlalkyl group, and alkyl group, R2: alkyl group, and phenylalkyl group, R3: hydrogen, sulfo group, alkyl group, phenyl group, and halogen atom, n=0 to 17, and x=0 to 1) or a slat of its derivative. The aqueous solution incorporates about 0.1-5% the above described compound and further the solution containing an orgnic acid, an inorganic acid and a metallic compound is preferred and moreover an ammonia slat or the like is added, if necessary. A printed wiring board with reliability is produced by performing a solder reflow treatment, a soldering treatment, and an alkaline solution treatment, etc., after the above described surface treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention relates to rust prevention, solder roughening, discoloration prevention, alkali resistance, moisture resistance and chemical resistance of metals such as copper, copper alloys, solders, electroless solders, nickel, silver and zinc. The present invention relates to a treatment method for improving heat resistance and solderability, and is particularly suitable for maintaining the solderability of these metals in a good state for a long period of time and preventing surface roughness due to an alkaline solution during printed wiring board manufacturing. It provides a simple method. 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.

[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 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. The pre-flux used for the purpose of preventing rust on the circuit part made of copper or copper alloy and maintaining solderability is
There are roughly two types: a rosin-based preflux that coats the entire printed wiring board and an alkylimidazole-based preflux that selectively chemically reacts with copper or a copper alloy. For the former, apply natural rosin, rosin ester, rosin-modified maleic acid resin, etc. dissolved in an organic solvent with a roll coater, or apply it to the entire printed wiring board by spraying or dipping, and then dry to form a film. Used in the method. Therefore, there is a drawback in that the working environment and safety are significantly impaired by the volatilization of the organic solvent. In addition, since rosin-based preflux uses a volatile solvent, it also has a drawback that it may cause a fire when working.

[0003]

In the above-described method for manufacturing a printed wiring board, the reliability as a solder etching resist film is poor and a manufacturing defect is likely to occur. Therefore, at the time of peeling an alkali developing type photosensitive film and at the time of alkali etching. To prevent the solder from becoming rough and to obtain good circuit formation, and to maintain 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 and zinc are treated with a safe solution containing no harmful hexavalent chromium compound to prevent discoloration for a long period of time and maintain good solderability. The surface mounting method is often 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. Further, it is desired to develop a preflux which does not use a volatile solvent having a problem in air pollution and has excellent wettability and solderability of cream solder even after being exposed to a high temperature.

[0004]

In view of such circumstances, the present inventor has taken into consideration the above-mentioned circumstances, and when the alkali developing type photosensitive film is peeled off, the solder is roughened during alkali etching, and a solder rust preventive agent for preventing discoloration and an electroless solder are used. anti-rust. In addition, it is a rust preventive agent with excellent rust prevention, moisture resistance, heat resistance, and solderability for connector parts and nickel substrates. In addition, it is a surface protective agent that forms a chemical conversion film on the copper circuit and withstands alkaline solutions. Also, the wettability of the low melting point cream solder even after being exposed to high temperature, spreadability, solderability after reflow, as a result of extensive studies on a heat-resistant water-soluble preflux agent with good wettability, in the practice of the present invention. As the organic acid used,
Acetic acid, iodoacetic acid, bromoacetic acid, dimethylacetic acid, diethylacetic acid, α-bromoacetic acid, paranitrobenzoic acid, paratoluenesulfonic acid, picric acid, oxalic acid, formic acid, succinic acid, maleic acid, acrylic acid, fumaric acid, tartaric acid, adipine Acids, lactic acid, oleic acid, citric acid, metasulfonic acid, sulfamic acid and other organic acids, hydrochloric acid, sulfuric acid, phosphorous acid, phosphoric acid and other inorganic acids, other carboxylic acids, halogenated fatty acids, halogenated aromatic carboxylic acids, etc. Therefore, it may be added at a rate 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 examples of the compound as a metal ion used in 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, phosphorus It is a metal compound such as copper oxide, copper carbonate, copper acetate, and copper sulfate, and is 0.00 with respect to water.
It may be added at a rate of 1 to 5%. The halogenated aromatic carboxylic acid used in the practice of the present invention is 3
-Bromo-4-methylbenzoic acid, 4- (bromomethyl) phenylacetic acid, α-bromophenylacetic acid, α-bromotetradecanoic acid, 2-bromophenylacetic acid, 3-bromophenylacetic acid, 4-bromophenylacetic acid, etc. In the range of 0.01 to 20%, preferably 0.1 to 5
% May be added. Examples of the halogenated fatty acid used in the practice of the present invention include bromoacetic acid, 3-bromo-2- (bromomethyl) propionic acid, 2-bromobutanoic acid, 4-bromobutanoic acid, 2-bromohexanedecanoic acid, 2-bromohexanoic acid. , 2-bromo-3-methylbutanoic acid, 2-bromo-2-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. In the range of 0.01 to 20%, preferably 0.1 to 5%. In the practice of the invention,
When it becomes difficult to dissolve the compounds represented by (Chemical Formula 1) to (Chemical Formula 5) and organic acids, metal compounds, halogenated aromatic carboxylic acids, and halogenated fatty acids, emulsification or methanol, ethanol, isopropyl alcohol, butanol Water-soluble solvents such as acetone and acetone can be used alone, respectively, and can also be used by mixing them at an arbitrary ratio. For example, the water-soluble solvent may be used in combination with other organic acids or the like, which are used alone.
When it becomes difficult to dissolve the compound represented by (Chemical formula 1) to (Chemical formula 5) or its derivative, it is preferable to add a water-soluble solvent, and the content ratio in this case is 0.01 to 60.
It is often appropriate to set it as%. It should be noted that adding a substance having a buffering action such as aqueous ammonia or amines to the treatment liquid is effective not only for enhancing the stability of PH of the aqueous solution but also for accelerating the film formation rate. To apply a rust-preventive conversion coating, a heat-resistant conversion coating, and a chemical-resistant conversion coating to the metal surface with the metal surface treatment agent of the present invention,
Contact the metal with the treatment liquid. As a method of contacting, a method of dipping, spraying or coating is used. 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. In addition, after forming the rust preventive conversion film,
Infrared / near-infrared / far-infrared / ultraviolet irradiation treatment is 0 as a treatment to further improve moisture resistance, heat resistance, and chemical resistance.
It is effective to perform the treatment at a temperature range of up to 300 ° C for a treatment time of several seconds to several tens of minutes.

[0005]

According to the above-mentioned treatment method, (Chemical formula 1) to (Chemical formula 5) which are effective for rust prevention on metal surfaces such as solder, electroless solder, nickel, silver, zinc, copper and copper alloy are mainly used. A rustproof chemical conversion coating, a heat resistant chemical conversion coating, and a chemical resistant chemical conversion coating are formed. These chemical conversion coatings are water-repellent, 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, spreadability, solder rise after reflow, and wettability of low melting point cream solder. It is good. Further, it is possible to manufacture a printed wiring board excellent in terms of working environment and safety.

[0006]

EXAMPLES Compounds represented by (Chemical formula 1) to (Chemical formula 5) (Table 1
1% of the compound described in 1), succinic acid, carboxylic acid, aqueous ammonia, cupric chloride, ion-exchanged water, etc., to prepare an aqueous solution of each type, and put it in a 100 ml container at a liquid temperature of 40 ° C.
It was heated and adjusted. On the other hand, 1 cm x 5 cm x 0.3 mm
The copper plate of No. 1 was electrosolder plated, electroless solder plated, nickel plated, copper sulfate plated, and silver plated. Next, degreasing, washing with water, soft etching, washing with water, pickling, washing with water to wash the surface, and then adding 6% to each type of 1% solution containing the compound represented by the above (Chemical formula 1) to (Chemical formula 5) as an active ingredient.
It was immersed for 0 seconds. After that, the sample pieces washed with water were prepared, and then the sample piece of (1) was put in a hot air dryer to obtain 200
It was heated at 0 ° C. for 10 minutes, immersed in post flux before measurement, and the wetting time was measured using a solder wettability tester.
Moisture resistant (MIL-STD-202)
After FM-106E) treatment, the test piece was immersed in post flux and the wetting time was measured using a solder wettability tester. (3) heating the alkaline solution to 40 ° C.,
~ The test piece was immersed for 5 minutes. After that, wash with water and check the surface condition (roughness, discoloration). The sample piece of (4) was subjected to a gas corrosion test (1 ± 0.3 ppm H ₂ S, 25 ± 2 ° C., 5% R
H, 10 days) metal surface condition (roughness, discoloration)
I see. The test results are shown in Table 1.

[Table 1]

[0007]

EFFECTS OF THE INVENTION According to the metal rust preventive treatment method of the present invention, excellent moisture resistance, chemical resistance and heat resistance can be obtained on metal surfaces such as solder, electroless solder, nickel, silver, zinc, copper and copper alloys. The chemical conversion coating forms not only to prevent rusting of the metal surface, but also to improve the wettability of solder, spreadability of solder, solderability after reflow, and good wettability. This is particularly effective for surface mounting. In addition, it not only prevents the solder from roughening during the alkaline aqueous solution treatment at the time of manufacturing the printed wiring board by the pattern plating method and eliminates the risk of circuit disconnection, but also leaves the solder at the soldering part and has good solderability without fusing treatment. Can be kept at. Further, it is possible to manufacture a printed wiring board and a metal component which are excellent in terms of work environment and safety.

Claims (7)

[Claims] 1. A method for surface treatment of a metal, which comprises contacting with an aqueous solution containing a salt of a compound represented by (Chemical formula 1) to (Chemical formula 5) or a derivative thereof. [Chemical 1] [Chemical 2] [Chemical 3] [Chemical 4] [Chemical 5] 2. A method for surface treatment of a metal, which comprises contacting with an aqueous solution containing a compound represented by (Chemical formula 1) to (Chemical formula 5) and an organic acid, an inorganic acid or a metal compound. 3. A method for surface treatment of a metal, which comprises contacting the compound represented by (Chemical formula 1) to (Chemical formula 5), an organic acid, an inorganic acid, and an aqueous solution containing an ammonium salt with a metal compound. 4. A method of manufacturing a printed wiring board, which comprises performing a solder reflow treatment after the surface treatment of the metal according to any one of claims 1 to 3. 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 3. 6. After the surface treatment of the metal according to any one of claims 1 to 3, 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 for manufacturing a printed wiring board, which comprises performing an alkaline solution treatment after surface treatment with a solution containing the compounds represented by (Chemical formula 1) to (Chemical formula 5), an organic acid, and a metal compound.