KR20050115652A - Preflux for printed wiring board - Google Patents

Abstract

The present invention relates to a preflux for printed wiring boards.

The preflux of the present invention contains a 2-pyridylbenzimidazole-based compound represented by Formula 1 as an active ingredient, and has a chemical layer having excellent heat resistance and solderability on a copper or copper alloy surface on the printed wiring board when the printed wiring board is applied. To form.

Formula 1

(Wherein R ₁ is H or an alkyl group having 1 to 10 carbon atoms, R ₂ is H or an alkyl group having 1 to 3 carbon atoms)

Description

Preflux For Printed Wiring Board

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous surface treatment agent applicable to the surface of copper or copper alloy, wherein the chemical layer is on a printed circuit board on a rigid printed circuit board (also referred to as a 'PWB') or a flexible printed circuit board. The present invention relates to a preflux for a printed wiring board having a high heat resistance and solderability.

Preflux is a surface treatment agent used for the purpose of rust-proofing circuit wiring which solders on PWB and maintaining solderability. However, as a method of bonding electronic components to PWB, surface mount method (SMT) has been widely used in recent years, and PWB has been subjected to high temperature due to temporary fixing of chip components, double-sided mounting of component devices, or mixing of chip components and discrete components. Exposed. Therefore, the preflux for protecting the copper circuit on the PWB must satisfy excellent heat resistance.

There are two types of preflux: resin-based preflux which largely covers the entire PWB, and alkylimidazole-based preflux which is optionally chemically reacted with copper or copper alloy. Among these, resin-based preflux is used as a method of dissolving natural rosin, rosin ester, rosin-modified maleic acid resin, etc. in an organic solvent, and then coating and drying the entire PWB to form a film. Such resin-based preflux uses an organic solvent. Therefore, the solvent has a drawback that volatilizes the air and significantly impairs the environment and safety.

On the other hand, the alkylimidazole-based preflux is water soluble and thus is widely used because of its excellent working environment and stability. However, the alkylimidazole compound having an alkyl group in the 2-position is poor in heat resistance, and when the alkylimidazole complex reacted with the copper or copper alloy of PWB is exposed to high temperature, it reacts with oxygen in the air to produce copper and copper The surface of the alloy decomposes and oxidizes, and has the drawback of poor solderability by inhibiting the action of postflux.

Therefore, many surface treatment agents which use a benzimidazole type compound as an active component have been developed instead of the alkylimidazole type preflux which is poor in heat resistance. By way of example, PWB using a 5-methylbenzimidazole compound, a 2-alkylbenzimidazole compound, a 2-arylbenzimidazole compound, a 2-aralkylbenzimidazole compound and a 2-mercaptoalkylbenzimidazole compound The surface treatment method of is disclosed in many Japanese Patent Laid-Open Publications.

According to the method of preserving solderability by using a preflux containing such a benzimidazole compound as an active ingredient, a chemical layer having good heat resistance can be formed on the copper surface.

However, in actual use, there is a problem that benzimidazole compounds easily precipitate as crystals as the pH of the prepared treatment solution rises or the treatment solution evaporates. The solid benzimidazole-based compound once crystallized is difficult to dissolve the active ingredient substance once precipitated even when the organic acid is added or the evaporated water is replenished to maintain the proper pH of the treatment solution. If the benzimidazole compound is crystallized or precipitated during the application of the copper surface of the PWB, the merchandise value of the PWB is significantly reduced.

Therefore, there is still a need for the development of preflux that has better heat resistance than existing preflux and is not easily precipitated or crystallized.

Accordingly, the present inventors have made diligent research efforts to solve the above problems. As a result, by containing 2-pyridylbenzimidazole-based compound represented by Formula 1 as an active ingredient or additionally containing an organic acid, excellent heat resistance and The present invention has been completed by being able to manufacture a preflux for PWB having solderability and at the same time having an effect that the active ingredient of the preflux is not easily precipitated during use.

The present invention overcomes the limitations of the conventional preflux for PWB as described above, and has a stability of a solution that does not easily precipitate solid materials in the solution during use, and the chemical layer formed on the surface of copper and copper alloy has significantly improved heat resistance. And it aims at providing the preflux for the printed wiring board which has solderability.

The present invention provides a preflux for a printed wiring board containing a 2-pyridylbenzimidazole compound represented by the following formula (1) as an active ingredient.

(Wherein R ₁ is H or an alkyl group having 1 to 10 carbon atoms, R ₂ is H or an alkyl group having 1 to 3 carbon atoms)

Hereinafter, the present invention will be described in more detail.

The preflux for printed wiring boards of this invention contains the 2-pyridyl benzimidazole type compound represented by the said Formula (1) as an active ingredient.

The 2-pyridylbenzimidazole compound is substituted with a pyridyl group in which the 2-position of the benzimidazole ring is one of the heterocyclic compounds.

Representative examples of compounds suitable for inclusion as active ingredients of the invention include 2-pyridylbenzimidazole, 2-pyridyl-4-methylbenzimidazole, 2-pyridyl-5-methylbenzimidazole, 2-pyri Dyl-6-methylbenzimidazole, 2-pyridyl-4-ethylbenzimidazole, 2-pyridyl-5-ethylbenzimidazole, 2-pyridyl-6-ethylbenzimidazole, 2-pyridyl- 4-propylbenzimidazole, 2-pyridyl-5-propylbenzimidazole, 2-pyridyl-6-propylbenzimidazole, 2- (5-methylpyridyl) benzimidazole, 2- (5-methyl Pyridyl) -4-methylbenzimidazole, 2- (5-methylpyridyl) -5-methylbenzimidazole, 2- (5-methylpyridyl) -6-methylbenzimidazole, 2- (5- Methylpyridyl) -4-ethylbenzimidazole, 2- (5-methylpyridyl) -5-ethylbenzimidazole, 2- (5-methylpyridyl) -6-ethylbenzimidazole, 2- (5 -Ethylpyridyl) benzimidazole, 2- (5-ethylpyridyl) -4-methylbenzimidazole, 2- (5-ethylpyridyl) -5-methylbenzimidazole, 2- (5-ethylpyrid Dill) 6-methylbenzimidazole, 2- (5-ethylpyridyl) -4-ethylbenzimidazole, 2- (5-ethylpyridyl) -5-ethylbenzimidazole, 2- (5-ethylpyridyl) -6-ethylbenzimidazole, 2- (5-propylpyridyl) benzimidazole, 2- (5-propylpyridyl) -4-methylbenzimidazole, 2- (5-propylpyridyl) -5- Methylbenzimidazole, 2- (5-propylpyridyl) -6-methylbenzimidazole, 2- (5-propylpyridyl) -4-ethylbenzimidazole, 2- (5-propylpyridyl) -5 -Ethylbenzimidazole, 2- (5-propylpyridyl) -6-ethylbenzimidazole, 2- (5-butylpyridyl) benzimidazole, 2- (5-butylpyridyl) -4-methylbenz Imidazole, 2- (5-butylpyridyl) -5-methylbenzimidazole, 2- (5-butylpyridyl) -6-methylbenzimidazole, 2- (5-butylpyridyl) -4-ethyl Benzimidazole, 2- (5-butylpyridyl) -5-ethylbenzimidazole, 2- (5-butylpyridyl) -6-ethylbenzimidazole, 2- (5-pentylpyridyl) benzimidazole , 2- (5-pentylpyridyl) -4-methylbenzimidazole, 2- (5-pentylpyridyl) -5-meth Benzimidazole, 2- (5-pentylpyridyl) -6-methylbenzimidazole, 2- (5-pentylpyridyl) -4-ethylbenzimidazole, 2- (5-pentylpyridyl) -5- Ethylbenzimidazole, 2- (5-pentylpyridyl) -6-ethylbenzimidazole, 2- (5-hexylpyridyl) benzimidazole, 2- (5-hexylpyridyl) -4-methylbenzimid Dazole, 2- (5-hexylpyridyl) -5-methylbenzimidazole, 2- (5-hexylpyridyl) -6-methylbenzimidazole, 2- (5-hexylpyridyl) -4-ethylbenz Imidazole, 2- (5-hexylpyridyl) -5-ethylbenzimidazole, 2- (5-hexylpyridyl) -6-ethylbenzimidazole, 2- (5-heptylpyridyl) benzimidazole, 2- (5-heptylpyridyl) -4-methylbenzimidazole, 2- (5-heptylpyridyl) -5-methylbenzimidazole, 2- (5-heptylpyridyl) -6-methylbenzimidazole , 2- (5-heptylpyridyl) -4-ethylbenzimidazole, 2- (5-heptylpyridyl) -5-ethylbenzimidazole, 2- (5-heptylpyridyl) -6-ethylbenzimid And other salts thereof.

In the preflux for PWB of the present invention, the content of the 2-pyridylbenzimidazole compound as described above is preferably 0.05% by weight to 1.0% by weight.

When the amount of the 2-pyridylbenzimidazole compound represented by Chemical Formula 1 in the total preflux is less than 0.05% by weight, the formation rate of the chemical layer on the surface of copper and copper alloy is very slow, and the concentration of the compound is 1.0% by weight. In the above case, since it is difficult to obtain an aqueous solution and a large amount of organic acid must be added, it is not preferable.

Meanwhile, the preflux for PWB of the present invention may further include an organic acid, a copper compound, and other additives in addition to the active ingredient. The proportion of such additives in the water-soluble preflux of the present invention is preferably 20% or less of the total weight.

Since the 2-pyridylbenzimidazole-based compound represented by the formula (1) included in the preflux of the present invention is poorly soluble in water, in order to dissolve them in water, benzimidazole is reacted with an organic acid and soluble in water. You can make it with one salt.

In particular, preferably a C ₄ aliphatic carboxylic acid with the 2-pyridyl benzimidazole-based compound in an aqueous solution containing 1% by weight to 15% by weight or less of the particular organic acid is soluble.

Therefore, the preflux of the present invention preferably further contains 1 to 15% by weight of C ₄ or less aliphatic carboxylic acid. When the concentration of the carboxylic acid is lower than 1% by weight, the 2-pyridylbenzimidazole-based compound may not be completely dissolved, and when the concentration of the carboxylic acid exceeds 15% by weight, the PWB manufacturing apparatus may be corroded.

Preferred examples of such C ₄ or less aliphatic carboxylic acid include, but are not limited to, formic acid, acetic acid, propionic acid and butyric acid.

On the other hand, in order to further improve the heat resistance of the chemical layers formed on the copper and copper alloy surfaces, the formation rate of the chemical layer can be increased by adding a copper compound to the preflux of the present invention. It is also possible to use higher fatty acids as additives.

In the preflux treatment process of the present invention, the polished and degreased PWB main body is immersed in a solution of sodium persulfate (200 g / L, 30 ° C.) for 20 to 30 seconds, soft etched and washed with water, and the PWB is washed with a room temperature solution of 3% hydrochloric acid. After immersing for 20 seconds to pickle and washing with water again, the metal surface is immersed in the treatment liquid or the treatment liquid is applied or sprayed onto the metal surface. At this time, preferable conditions are pH 3.5-3.9, and the temperature of a processing agent is about 30-40 degreeC.

The PWB treated with the preflux of the present invention containing the compound represented by the above formula (1) has significantly improved heat resistance compared to the PWB treated with an alkylimidazole compound having an alkyl group at the 2-position or a conventional benzimidazole compound. Excellent solderability. In addition, the preflux of the present invention, which further contains an aliphatic carboxylic acid of C ₄ or less as an organic acid, is highly dissolved in the benzimidazole compound and is not easily precipitated during use.

Hereinafter, the configuration and operation of the present invention through the examples and comparative examples will be described in more detail. However, it is apparent to those skilled in the art that the present invention is not limited only to these examples.

<Example 1>

Preflux was prepared by mixing 0.25% 2- (5-ethylpyridyl) benzimidazole, 10% acetic acid, 0.05% fatty acid and 0.05% copper acetate and adjusting the pH to 3.8 using ammonia acetate. After immersing the copper specimen for 60 seconds while maintaining the temperature of the prepared preflux at 40 ℃, the specimen was taken out, washed with water and dried. The heat resistance and the solderability of the dried copper specimens were measured in the following manner, and the results are shown in Table 1.

Heat resistance and solderability measurement

The preflux treated copper specimens were oxidized at 170 ° C. for 100 seconds and then oxidized at 260 ° C. for 60 seconds three times. The thickness of the formed coating film was measured using an ultraviolet spectrophotometer, and the presence of oxidation traces on the surface of the specimen and the degree of solderability were visually observed.

<Example 2>

Preflux was prepared by mixing 0.25% 2- (5-propylpyridyl) benzimidazole, 13% acetic acid, 0.05% fatty acid and 0.05% copper bromide and adjusting the pH to 3.8 using ammonia acetate. After immersing the copper specimen for 60 seconds while maintaining the temperature of the prepared preflux at 40 ℃, the specimen was taken out, washed with water and dried. The heat resistance and the solderability of the dried copper specimens were measured in the same manner as above, and the results are shown in Table 1.

<Example 3>

After mixing 0.25% 2- (5-propylpyridyl) -6-ethylbenzimidazole, 15% acetic acid, 0.05% fatty acid and 0.05% copper acetate, the pH was adjusted to 3.8 using ammonia acetate to adjust the preflux. Prepared. After immersing the copper specimen for 60 seconds while maintaining the temperature of the prepared preflux at 40 ℃, the specimen was taken out, washed with water and dried. The heat resistance and the solderability of the dried copper specimens were measured in the same manner as above, and the results are shown in Table 1.

<Example 4>

Preflux was prepared by mixing 0.25% 2- (5-heptylpyridyl) benzimidazole, 13% acetic acid, 0.05% fatty acid and 0.05% copper bromide and adjusting the pH to 3.8 using ammonia acetate. After immersing the copper specimen for 60 seconds while maintaining the temperature of the prepared preflux at 40 ℃, the specimen was taken out, washed with water and dried. The heat resistance and the solderability of the dried copper specimens were measured in the same manner as above, and the results are shown in Table 1.

Example 5

Preflux was prepared by mixing 0.25% 2- (5-heptylpyridyl) benzimidazole, 10% acetic acid, 0.05% fatty acid and 0.05% copper acetate, and then adjusting the pH to 3.8 using ammonia acetate. After immersing the copper specimen for 60 seconds while maintaining the temperature of the prepared preflux at 40 ℃, the specimen was taken out, washed with water and dried. The heat resistance and the solderability of the dried copper specimens were measured in the same manner as above, and the results are shown in Table 1.

Comparative Example 1

Preflux was prepared by mixing 0.25% 2-pentylimidazole, 10% acetic acid, 0.05% fatty acid and 0.05% copper acetate, and then adjusting the pH to 3.8 using ammonia acetate. After immersing the copper specimen for 60 seconds while maintaining the temperature of the prepared preflux at 40 ℃, the specimen was taken out, washed with water and dried. The heat resistance and the solderability of the dried copper specimens were measured in the same manner as above, and the results are shown in Table 1.

Comparative Example 2

Preflux was prepared by mixing 0.25% 2- (5,6-dimethylbenzyl) benzimidazole, 10% acetic acid, 0.05% fatty acid and 0.05% copper acetate and adjusting the pH to 3.8 with ammonia acetate. After immersing the copper specimen for 60 seconds while maintaining the temperature of the prepared preflux at 40 ℃, the specimen was taken out, washed with water and dried. The heat resistance and the solderability of the dried copper specimens were measured in the same manner as above, and the results are shown in Table 1.

Comparative Example 3

Preflux was prepared by mixing 0.25% 2- (5-propylbenzyl) -6-ethylbenzimidazole, 10% acetic acid, 0.05% fatty acid and 0.05% copper acetate, and then adjusting the pH to 3.8 using ammonia acetate. It was. After immersing the copper specimen for 60 seconds while maintaining the temperature of the prepared preflux at 40 ℃, the specimen was taken out, washed with water and dried. The heat resistance and the solderability of the dried copper specimens were measured in the same manner as above, and the results are shown in Table 1.

Coating thickness (㎛) Heat resistance (with or without oxidation) Solderability Example 1 0.15 No oxidation traces 100% Example 2 0.20 No oxidation traces 100% Example 3 0.20 No oxidation traces 100% Example 4 0.25 No oxidation traces 100% Example 5 0.18 No oxidation traces 100% Comparative Example 1 0.20 Browning 55% Comparative Example 2 0.16 Browning 45% Comparative Example 3 0.17 Browning 60%

As described in detail above, according to the water-soluble preflux for PWB of the present invention containing 2-pyridylbenzimidazole-based compound represented by the formula (1) as an active ingredient, a film having heat resistance on the surface of copper or copper alloy It can form, and especially solderability can be improved in the surface mounting method of PWB.

On the other hand, while the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art to which the present invention pertains without departing from the spirit and scope of the present invention described in the claims below It will be understood that modifications and changes can be made.

Claims (3)

A preflux for a printed wiring board, characterized in that it contains a 2-pyridylbenzimidazole compound represented by the following formula (1) as an active ingredient: Formula 1 (Wherein R ₁ is H or an alkyl group having 1 to 10 carbon atoms, R ₂ is H or an alkyl group having 1 to 3 carbon atoms) The preflux for printed wiring board according to claim 1, wherein the content of the benzimidazole compound represented by Chemical Formula 1 is 0.05% by weight to 1.0% by weight. Article according to any one of the preceding claims, C ₄ aliphatic carboxylic acid 1 is characterized by a printed wiring board free flux further contains a weight% to 15 weight% or less.