JP2575242C - - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface protective agent for a printed wiring board. In particular, the present invention relates to a surface protective agent for a printed wiring board having an excellent effect of preventing oxidation of a metal surface of a printed wiring board at high temperature or generation of rust under high humidity. Conventionally, a printed wiring board generally uses a metal plate made of copper or a copper alloy on a circuit surface thereof. As a method of protecting the surface of the printed wiring board, a resin coating method, a solder coating method, and a coating method using a chemical agent are used. It is roughly divided. The above resin coating method generally involves dissolving rosin, synthetic resin, etc. in an organic solvent, applying it to the entire surface of the printed wiring board by means of a roller, brush, dipping, spraying, etc., and then drying it to form a film. Is the way. Further, the solder coating method is a method of protecting a circuit surface of a printed wiring board by thinly coating a molten solder with a repeller or the like. In the above-mentioned resin coating method, since an organic solvent solution of a resin is used, vaporization and dissipation of the organic solvent are extremely inconvenient in terms of environmental hygiene such as worker poisoning and work fire. In addition, although the solder coating method has excellent protection characteristics of the printed wiring board under high temperature or high humidity, the thickness of the solder coating by the solder coating is not constant, so it is not suitable for high-density mounting of current parts It is. In addition, the cost for coating the solder is relatively high, which is disadvantageous in industrial mass production. [0003] In order to obviate the drawbacks of the printed wiring board protection method described above, a method of protecting a rust-preventive coating with a chemical has been developed. Further, a method for preventing rust of copper and copper alloys using an imidazole derivative as a rust preventive agent has been disclosed (Japanese Patent Publication No. 46-17046,
JP-B-46-34214). However, these agents have a drawback that they deteriorate the solderability under high temperature and high humidity. Accordingly, a benzimidazole derivative is disclosed as a protective agent which has been attempted to solve the above-mentioned disadvantages. (JP-A-3-124395). [0004] Even in the case of the protective agent containing a penzimidazole derivative of the prior art as a main component described in the preceding section, recent years have seen an urgent need for higher density and surface mounting of components mounted on printed wiring boards. I am doing it. In addition, it is difficult to achieve sufficient rust-preventive hardening not only at the time of soldering but also under conditions such as a curing oven or a reflow oven where the time during which the printed wiring board is exposed to high temperatures is increased. An object of the present invention is to provide a novel protective agent which can sufficiently satisfy the above-mentioned severe conditions using a protective agent containing a substituted benzimidazole derivative as a main component in a printed wiring board. The inventor of the present invention has enthusiastically studied the replacement of a protective agent which is sufficiently effective even under the above-mentioned severe processing conditions of a printed wiring board. The inventors have found that a benzimidazole derivative and a salt thereof can satisfy the requirement, and have completed the present invention. The present invention is a surface protective agent for a printed wiring board, comprising a compound represented by Chemical Formula 1 as an active ingredient. Embedded image (Wherein X is a same or different alkyl groups having 1 to 7 carbon atoms, halogen atoms, di lower <br/> class alkylamino group, hydroxy group, shea Anomoto, an acetyl group, or a nitro group, Y represents a 1-20C straight-chain or branched-chain alkyl group having a carbon, n represents indicates an integer of 1 to 4, provided that when X is only an alkyl group having 1 to 7 carbon atoms, n represents 3 Or an integer of 4 , wherein (X) n is such that n is 1, 2 or 3 and the substitution position is 4-position, 5-position and 6
X is a lower alkyl group, a halogen atom and
Excluding those selected only from the group consisting of nitro and nitro groups. The compounds represented by Chemical Formula 1 as active ingredients of the protective agent of the present invention include 4,5,6
, 7-Tetramethyl-2-n-propylbenzimidazole , 6 -diethylamino-2-n-decylbenzimidazole, 6-hydroxy-2-n-eicosabenzimidazole, 4,7-dicyano-2-n-octyl Benzimidazole ,
4, 6-diacetyl-2-isobutyl-benzimidazole, 4, 5-dimethyl -
7-acetyl-2-hexylbenzimidazole and the like. In order to use the compound represented by Chemical Formula 1 as an active ingredient of the present invention as a surface protective agent for a printed wiring board of the present invention, the compound is dissolved in water or an aqueous solvent miscible with water at an arbitrary ratio. Alternatively, it is convenient to use an emulsified state. Since the compound represented by Chemical Formula 1 is generally insoluble in water, when this compound is formed into a salt with an inorganic acid or an organic acid to form an aqueous solution, it becomes a protective agent which can be easily used. 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,
Organic acids such as fluoroacetic acid, difluoroacetic acid, trifluoroacetic acid, oxalic acid, malonic acid, succinic acid, adipic acid, malic acid, tartaric acid, citric acid, maleic acid, fumaric acid, paratoluenesulfonic acid, methanesulfonic acid, etc., hydrochloric acid And inorganic acids such as sulfuric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, and nitric acid. Examples of the solvent arbitrarily miscible with water include methanol, ethanol, isopropanol, acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, dimethyl sulfoxide, and dimethylformamide.In the case of the protective agent of the present invention, these solvents are necessary. May be added as appropriate. The content of the active ingredient contained in the present solution or emulsion is 0.05 to 30% (weight)
, Desirably 0.1 to 5% (by weight). The content of the active ingredient is 0.05% (
If the amount is less than 30% (weight), a sufficient protective effect cannot be obtained even if a printed wiring board is applied using this agent. If the amount exceeds 30% (weight), insoluble components tend to increase, and it is economically disadvantageous. is there. [0009] In addition to the above-mentioned active ingredients, the protective agent for printed wiring boards of the present invention includes, for example, copper formate, copper chloride, copper oxalate, copper acetate, copper phosphate, sulfuric acid as an auxiliary agent for forming a complex film with copper. It is preferable to add heavy metal salts such as copper, copper formate, manganese formate, manganese chloride, manganese oxalate, and manganese sulfate. Other auxiliaries usually added to the protective agent used for the purpose of the present invention may be appropriately added. In the method of forming a protective film on a printed wiring board with the protective agent of the present invention, the surface of a copper circuit of the printed wiring board is finished by mechanical or chemical polishing according to a general coating method, and then the protective film of the present invention is protected. Immerse in the agent solution. The immersion can usually be carried out in the range of 0 to 60 ° C, but preferably 10 to 50 ° C. The immersion time is 5 seconds to 1 hour, preferably 10 seconds to 10 minutes. It should be noted that other application methods such as a spraying method, a brush, a coating method using a roller or the like may be used. The coating film obtained as described above has extremely good solderability even under high temperature and high humidity. Next, embodiments of the present invention and effects thereof will be described. EXAMPLE 1 0.1 g of copper sulfate, 4,5,6,7-
1.0 g of tetramethyl-2-n-propylbenzimidazole and 0.1 g of 25% aqueous ammonia were sequentially added and mixed to obtain an aqueous solution of 4,5,6,7-tetramethyl-2-n-propylbenzimidazole. . A test piece having a surface cleaned by polishing, degreasing, soft etching, and washing a 30.0 mm × 7.5 mm × 0.3 mm copper plate was immersed in this solution at 50 ° C. for 2 minutes. After this coating, it is washed with water, dried with warm air, and then placed in an air circulation oven at 200 ° C. for 5 minutes.
Heat deterioration was performed for 10 minutes, 15 minutes, and 20 minutes, a post flux was applied before measurement, and a solder wetting test method (equilibrium method) was performed according to JIS-C-0053. The solder spread rate test was performed in accordance with JIS-Z-3197. Table 1 shows the results.
Further, 0, 100, 200, 500, 10
Table 2 shows the results of the solder wetting test and the solder spreading test performed after 00 hours in the same manner as the previous test. Example 3 25 g of ethanol and 10 g of 6-diethylamino-2-n-decylbenzimidazole were added to 75 g of a tartaric acid aqueous solution of 3 (% by weight) and mixed with it to obtain an aqueous solution of 6-diethylamino-2-n-decylbenzimidazole. . A test piece similar to that of Example 1 was immersed in this liquid, and a solder wetting test, a solder spread rate test, a solder wetness test under high humidity, and a solder spread rate test were similarly performed. The results are shown in Tables 1 and 2. Was. Example 4 To 75 g of a 3% (by weight) aqueous solution of tartaric acid was added 25 g of ethanol and 6-hydroxy-
1.0 g of 2-n-eicosabenzimidazole was added and mixed, and 6-hydroxy-
An aqueous solution of 2-n-eicosabenzimidazole was obtained. A test piece similar to that of Example 1 was immersed in this liquid, and a solder wetting test, a solder spread rate test, a solder wetness test under high humidity, and a solder spread rate test were similarly performed. The results are shown in Tables 1 and 2. Was. Example 5 0.1 g of manganese formate and 1.0 g of 4,7-dicyano-2-n-octylbenzimidazole were added to 100 g of a 2% (by weight) aqueous tartaric acid solution, and the mixture was mixed with 4,7-dicyano-2-. An aqueous solution of n-octylbenzimidazole was obtained. A test piece similar to that of Example 1 was immersed in this liquid, and a solder wetting test, a solder spread rate test, a solder wetness test under high humidity, and a solder spread rate test were similarly performed. The results are shown in Tables 1 and 2. Was. Example 7 1.0 g of 4,6-diacetyl-2-isobutylbenzimidazole was added to 100 g of a 2 (wt%) aqueous tartaric acid solution, and the same test piece as in Example 1 was immersed in this solution.
Similarly, solder wetting test, solder spread rate test and solder wetting test under high humidity,
A solder spread rate test was performed, and the results are shown in Tables 1 and 2. Comparative Example 1 In place of 4,5,6,7-tetramethyl-2-n-propylbenzimidazole in Example 1, 4-methyl-2-undecylimidazole was added in the same amount to give 4-methyl- An aqueous solution of 2-n-undecylimidazole was obtained, and the same test piece as in Example 1 was immersed in this liquid at room temperature for 30 seconds. The test pieces thus obtained were subjected to a solder wetness test, a solder spread rate test, a solder wetness test under high humidity and a solder spread rate test in the same manner as in Example 1, and the results are shown in Tables 1 and 2. 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 is added, and 0.05 g of copper chloride and 0.5 g of aqueous ammonia are added.
Was dissolved and the solution temperature was adjusted to 50 ° C. to obtain a 1% (by weight) aqueous solution of benzimidazole. A test piece similar to that of Example 1 was immersed in this liquid, and a solder wetting test, a solder spread rate test, a solder wetness test under high humidity, and a solder spread rate test were similarly performed. The results are shown in Tables 1 and 2. Was. [Table 1] [Table 2] As is clear from the above results, the protective agent of the present invention had a shorter solder wetting time, a better rust-preventive effect under high humidity, and a better solder wet time than the protective agent of the comparative example. The surface protective agent for printed wiring boards of the present invention forms a very good film on the surfaces of copper and alloy on printed circuit boards even after being exposed to heat resistance and high humidity. The present invention is a useful invention showing a remarkable effect on protection of a printed wiring board and solderability after component mounting.

Claims (1)

Claims: 1. A surface protective agent for a printed wiring board, comprising a compound represented by the formula 1 as an active ingredient. Embedded image (Wherein X is a same or different alkyl groups having 1 to 7 carbon atoms, halogen atoms, di lower <br/> class alkylamino group, hydroxy group, shea Anomoto, an acetyl group, or a nitro group, Y represents a 1-20C straight-chain or branched-chain alkyl group having a carbon, n represents indicates an integer of 1 to 4, provided that when X is only an alkyl group having 1 to 7 carbon atoms, n represents 3 Or (X) n is such that n is 1, 2 or 3 and the substitution position is 4-position, 5-position or 6
X is a lower alkyl group, a halogen atom and
Excluding those selected only from the group consisting of nitro and nitro groups. 2. The protective agent according to claim 1, comprising an aqueous solution of a salt of the compound represented by the formula (1) as an active ingredient.