JPH0525407A - Surface protectant for printed circuit board - Google Patents

Abstract

PURPOSE:To effectively prevent the surface of the metal on a printed circuit board from oxidizing or rusting at high temperatures by using a substituted benzimidazole as an active ingredient. CONSTITUTION:The objective surface protectant which comprises, as an active ingredient, a compound represented by the formula. In the formula, X is a 1-7C alkyl, a halogen atom, amino, a di(lower alkyl)amino, hydroxyl, a lower alkoxy, cyano, acetyl, benzoyl, carbamoyl, formyl, carboxyl, a lower alkoxycarbonyl, or nitro, Y is a 1-20C linear or branched alkyl, and (n) is an integer of 1 to 4. Examples of the compound include 6-methyl-2-n- propylbenzimidazole, 5,6-dichloro-2-n-hexylbenzimidazole, and 4-chloro-6n-heptyl-7- methoxy-2-ethylbenzimidazole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface protective agent for printed wiring boards. In particular, the present invention relates to a surface protective agent for a printed wiring board, which has an excellent effect of preventing oxidation of the surface of the printed wiring board metal at high temperature or generation of rust under high humidity.

[0002]

2. Description of the Related Art Conventionally, a printed wiring board is generally made of a metal plate made of copper or copper alloy on its circuit surface. As a method of protecting the surface of this printed wiring board, a resin coating method, a solder coating method, or a chemical coating method is used. It is roughly divided into laws. As the above resin coating method, generally, a rosin, a synthetic resin, etc. are dissolved in an organic solvent and applied on the entire surface of a printed wiring board by means of rollers, brushes, dipping, spraying, etc., and then dried to form a film. Is the way. In addition, the solder coating method is a method of protecting the circuit surface of the printed wiring board by thinly coating the molten solder with a leveler or the like. In the above resin coating method, since the organic solvent solution of the resin is used,
Due to vaporization and dispersion of the organic solvent, it was extremely inconvenient for environmental hygiene such as worker poisoning and work fire. In addition, the solder coating method has excellent protection characteristics against high temperature or high humidity of the printed wiring board, but the thickness of the solder coating by the solder coating is not constant and is not suitable for high-density mounting of current components. Is. Further, the cost is high because the solder is coated, which is disadvantageous in industrial mass production.

In order to eliminate the above-mentioned drawbacks of the printed wiring board protection method, a chemical anticorrosion film protection method has been developed. Then, a method of using a imidazole derivative as a rust-preventing agent to prevent rusting of copper and copper alloys is disclosed (Japanese Patent Publication Nos. 46-17046 and 46-34214). But,
These agents have a drawback that they deteriorate the solderability under high temperature and high humidity. Therefore, a benzimidazole derivative has been disclosed as a protective agent attempted to solve the above-mentioned drawbacks (JP-A-3-124395).

[0004]

Even in the case of the protective agent containing the benzimidazole derivative of the prior art as the main component described in the preceding paragraph, the recent trend toward densification and surface mounting of printed wiring board components is urgently needed. . In addition, not only during soldering, but also in conditions such as curing furnace, reflow furnace, etc. where the time during which the printed wiring board is exposed to high temperatures increases
It was difficult to achieve a sufficient rust prevention effect. An object of the present invention is to provide a novel protective agent which uses a protective agent containing a substituted benzimidazole derivative as a main component in a printed wiring board and can be sufficiently satisfied even under the above-mentioned severe conditions.

[0005]

The inventor of the present invention has conducted intensive studies on a protective agent having a sufficient effect even under the severe treatment conditions of the above-mentioned current printed wiring board. The present invention has been completed by finding that the imidazole derivative and its salt can satisfy the requirements.

The present invention is a surface protective agent for a printed wiring board, which comprises a compound represented by [Chemical formula 1] as an active ingredient.

[Chemical 1] (Wherein X is the same or different and is an alkyl group having 1 to 7 carbon atoms, a halogen atom, an amino group, a di-lower alkylamino group, a hydroxy group, a lower alkoxy group, a cyano group, an acetyl group, a benzoyl group, a carbamoyl group, Formyl group,
A carboxyl group, a lower alkoxycarbonyl group or a nitro group, Y represents a linear or branched alkyl group having 1 to 20 carbon atoms, and n represents an integer of 1 to 4)

The active ingredient of the protective agent of the present invention [Chemical formula 1]
The compound represented by 6-methyl-2-n-propylbenzimidazole, 4,5,6,7-tetramethyl-2-n
-Propylbenzimidazole, 5,6-dichloro-2-n-
Hexylbenzimidazole, 6-diethylamino-2-
n-decylbenzimidazole, 6-hydroxy-2-n-
Eicosabenzimidazole, 4,7-dicyano-2-n-
Octylbenzimidazole, 6-nitro-2-ethylbenzimidazole, 6-ethoxy-2-isopropylbenzimidazole, 6-amino-2-isooctylbenzimidazole, 4,6-diacetyl-2-isobutylbenzimidazole, 4-benzoyl -6-carbamoyl-2-n-propylbenzimidazole, 4,7-dimethoxycarbonyl-2-n-eicosabenzimidazole, 6-methoxycarbonyl-2-isopropylbenzimidazole, 4,5-
Dimethyl-7-acetyl-2-hexylbenzimidazole, 4-chloro-6-n-heptyl-7-methoxy-2-ethylbenzimidazole, 4,6-difluoro-5-formyl-
2-n-nonylbenzimidazole, 6-carbamoyl-
4,7-diethoxy-2-isobutylbenzimidazole and the like can be mentioned.

The compound represented by [Chemical Formula 1] which is the active ingredient of the present invention can be used as a surface protective agent for a printed wiring board of the present invention by water or an aqueous solvent in which water is mixed at an arbitrary ratio. It is convenient for use to be dissolved or emulsified in. Since the compound represented by [Chemical Formula 1] is generally insoluble in water, forming a salt of this compound with an inorganic acid or an organic acid to form an aqueous solution provides a protective agent that is easy to use.
In this case, the acid forming a salt includes formic acid, acetic acid, propionic acid, butyric acid, glycolic acid, lactic acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, bromoacetic acid, dibromoacetic acid, fluoroacetic acid, difluoroacetic acid, trifluoroacetic acid, oxalic acid. Organic acids such as acids, malonic acid, succinic acid, adipic acid, malic acid, tartaric acid, citric acid, maleic acid, fumaric acid, paratoluenesulfonic acid, methanesulfonic acid,
Inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, phosphorous acid, hypophosphorous acid and nitric acid are used. In addition, examples of the solvent that is miscible with water include methanol, ethanol, isopropanol, acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, dimethylsulfoxide, and dimethylformamide, and these solvents are required in the case of the protective agent of the present invention. You may add suitably according to. The content of the active ingredient contained in the present solution or emulsion is 0.05 to 30% (by weight),
It is preferably 0.1 to 5% (weight). If the content of the active ingredient is less than 0.05% (by weight), a sufficient protective effect cannot be obtained even if a printed wiring board is coated with this agent.
If it exceeds 30% (by weight), the amount of insoluble matter tends to increase, and it is economically disadvantageous.

In addition to the above-mentioned active ingredients, the protective agent for a printed wiring board of the present invention may be used as a complex film forming aid with copper, such as copper formate, copper chloride, copper oxalate, copper acetate, copper phosphate and sulfuric acid. It is preferable to add a heavy metal salt such as copper, copper formate, manganese formate, manganese chloride, manganese oxalate, or manganese sulfate. In addition, an auxiliary agent which is usually added to the protective agent used for the purpose of the present invention may be added appropriately.

The method of forming a protective film on a printed wiring board with the protective agent of the present invention is carried out in accordance with a general coating method by finishing the copper circuit surface of the printed wiring board by mechanical or chemical polishing, and then continuously protecting the present invention. Immerse in the solution of the agent. Immersion can usually be carried out in the range of 0 to 60 ° C, preferably 10 to 50 ° C. Immersion time is 5 seconds to 1 hour, preferably 10 seconds to 10
It's a minute. Other application methods such as a spray method, a brush, a roller and the like may be used. The coating film obtained as described above has extremely good solderability even under high temperature and high humidity.

Next, examples of the present invention and their effects will be shown.

[0012]

【Example】

Example 1 100 g of a 2% (wt)% tartaric acid aqueous solution, 0.1 g of copper sulfate, 6
-Methyl-2-n-propylbenzimidazole 1.0 g, 25
% Ammonia water 0.1g was added sequentially and mixed, and 6-methyl-
An aqueous 2-n-propylbenzimidazole solution was obtained. A test piece prepared by polishing, degreasing, soft etching, and washing the surface of a copper plate of 30.0 mm × 7.5 mm × 0.3 mm with this liquid to clean the surface at 50 ° C
And soaked for 2 minutes. After this coating, wash with water, dry with warm air, and then in an air circulation oven at 200 ° C for 5 minutes, 10 minutes, 1
After heat deterioration for 5 minutes and 20 minutes, post flux was applied before measurement, and a solder wetting test method (equilibrium method) was performed according to JIS-C-0053. Also, the solder spread rate test is JIS-Z-3197.
It was done according to. The results are shown in [Table 1], and the results of the solder wetting test and the solder spreading test after 0, 100, 200, 500, and 1000 hours under the condition of 90% humidity and 40 ° C are conducted in the same manner as the previous test. 2].

Example 2 To 100 g of a 2 (wt)% tartaric acid aqueous solution, 0.1 g of copper sulfate,
4,5,6,7-Tetramethyl-2-n-propyl benzimidazole (1.0 g) and 25% aqueous ammonia (0.1 g) were added sequentially and mixed to give 4,5,6,7-tetramethyl-2-n-propyl. An aqueous benzimiimidazole solution was obtained. The same test piece as in Example 1 was dipped in this solution, and similarly, a solder wetting test, a solder spreading rate test, a solder wetting test under high humidity, and a solder spreading rate test were conducted, and the results are shown in [Table 1] and [Table 1]. 2].

Example 3 5,6-dichloro-in 100 g of a 2% (by weight) aqueous tartaric acid solution
1.0 g of 2-n-hexylbenzimidazole was added and mixed to obtain an aqueous solution of 5,6-dichloro-2-n-hexylbenzimidazole. The same test piece as in Example 1 was dipped in this solution, and similarly, a solder wetting test, a solder spreading rate test, a solder wetting test under high humidity, and a solder spreading rate test were conducted, and the results are shown in [Table 1] and [Table 1]. 2].

Example 4 25 g of ethanol and 10 g of 6-diethylamino-2-n-decylbenzimidazole were added to 75 g of a 3% (wt)% tartaric acid aqueous solution.
g was added and mixed to obtain a 6-diethylamino-2-n-decylbenzimidazole aqueous solution. The same test piece as in Example 1 was dipped in this solution, and similarly, a solder wetting test, a solder spreading rate test, a solder wetting test under high humidity, and a solder spreading rate test were conducted, and the results are shown in [Table 1] and [Table 1]. 2].

EXAMPLE 5 25 g of ethanol and 1.0 g of 6-hydroxy-2-n-eicosabenzimidazole in 75 g of a 3% (wt)% tartaric acid aqueous solution.
g was added and mixed to obtain a 6-hydroxy-2-n-eicosabenzimidazole aqueous solution. The same test piece as in Example 1 was dipped in this solution, and similarly, a solder wetting test, a solder spreading rate test, a solder wetting test under high humidity, and a solder spreading rate test were conducted, and the results are shown in [Table 1] and [Table 1]. 2].

Example 6 0.1 g of manganese formate was added to 100 g of a 2% (by weight) aqueous tartaric acid solution.
1.0 g of 4-7-dicyano-2-n-octylbenzimidazole was added and mixed to obtain a 4-7-dicyano-2-n-octylbenzimidazole aqueous solution. The same test piece as in Example 1 was dipped in this solution, and similarly, a solder wetting test, a solder spreading rate test, a solder wetting test under high humidity, and a solder spreading rate test were conducted, and the results are shown in [Table 1] and [Table 1]. 2].

Example 7 0.1 g of manganese formate was added to 100 g of a 2% (by weight) aqueous tartaric acid solution.
1.0 g of 6-nitro-2-n-ethylbenzimidazole
Was added and mixed to obtain an aqueous solution of 6-nitro-2-n-ethylbenzimidazole. The same test piece as in Example 1 was dipped in this solution, and similarly, a solder wetting test, a solder spreading rate test, a solder wetting test under high humidity, and a solder spreading rate test were conducted, and the results are shown in [Table 1] and [Table 1]. 2].

Example 8 4,6-diacetyl-in 100 g of a 2 (wt)% tartaric acid aqueous solution
1.0 g of 2-isobutylbenzimidizole was added, and the same test piece as in Example 1 was immersed in this solution, and similarly, the solder wetting test, the solder spreading rate test, the solder wetting test under high humidity, and the solder spreading rate test were performed. And the results are shown in [Table 1].
And [Table 2].

Comparative Example 1 4-Methyl-2-n-undecylimidazole was added in the same amount as in Example 1, except that 6-methyl-2-n-propylbenzimidazole was replaced by 4-methyl-2-undecylimidazole. A solution similar to that of Example 1 was immersed in this solution for 30 seconds at room temperature. The test piece thus obtained was subjected to a solder wetting test, a solder spreading rate test, a solder wetting test under high humidity, and a solder spreading rate test in the same manner as in Example 1, and the results are shown in [Table 1] and [Table 2]. It was

Comparative Example 2 1 g of benzimidazole and 2 g of acetic acid were placed in a 300 ml beaker and stirred until dissolved. Next, 100 g of water was added, 0.05 g of copper chloride and 0.5 g of ammonia water were dissolved, and the liquid temperature was adjusted to 50 ° C. to obtain a 1 (wt)% benzimidazole aqueous solution.
The same test piece as in Example 1 was dipped in this solution, and similarly, a solder wetting test, a solder spreading rate test, a solder wetting test under high humidity, and a solder spreading rate test were conducted, and the results are shown in [Table 1] and [Table 1]. 2].

[0022]

[Table 1]

[0023]

[Table 2] As is clear from the above results, the protective agent of the present invention had a shorter solder wetting time than the protective agent of the comparative example, and had a good rust preventive effect under high humidity and a good solder wetting time.

[0024]

The surface protective agent for a printed wiring board of the present invention forms a very good film on the surfaces of copper and alloys on a circuit of a printed wiring board even after being exposed to heat resistance and high humidity. It is a useful invention that has a very remarkable effect on the protection of the board and the solderability after mounting the components.

Claims (2)

[Claims] 1. A surface protective agent for a printed wiring board, comprising a compound represented by [Chemical formula 1] as an active ingredient. [Chemical 1] (Wherein X is the same or different and is an alkyl group having 1 to 7 carbon atoms, a halogen atom, an amino group, a di-lower alkylamino group, a hydroxy group, a lower alkoxy group, a cyano group, an acetyl group, a benzoyl group, a carbamoyl group, Formyl group,
A carboxyl group, a lower alkoxycarbonyl group or a nitro group, Y represents a linear or branched alkyl group having 1 to 20 carbon atoms, and n represents an integer of 1 to 4) 2. The protective agent according to claim 1, which comprises an aqueous solution of a salt of the compound represented by [Chemical formula 1] as an active ingredient.