JPH0144033B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a printed circuit board cleaning liquid. In general, in the printed circuit board manufacturing process, the board becomes purple or yellow due to the effects of various chemicals and heat applied to the board during, for example, etching of plated copper foil, de-soldering operations, solder leveler, fusing, baking operations, etc. It has the disadvantage of turning brown (brown) and reducing the quality of the product. The inventors investigated the cause of such discoloration of printed circuit boards and found that the cause of the purple discoloration was due to gold ions in the plating bath when gold plating the terminal portions. In other words, when gold plating the terminal portion of a printed circuit board, if the processing liquid for the board in the previous step contains a substance that reacts with gold, the processing liquid adhering to the board and the gold ions in the plating bath may interact. The reaction produces a purple discoloration on the substrate.
Since this purple discolored substance penetrates into the inside of the substrate, it cannot be removed even by washing with hot water. The yellow (brown) discoloration of the substrate is thought to be due to the oxidation of the glass epoxy resin substrate due to the strong oxidizing action of the inorganic acid in the solder stripper. Therefore, the purpose of the present invention is to prevent the discoloration of the board that occurs during the conventional printed circuit board manufacturing process, and to eliminate the conventional process of removing the discolored board using emery paper or other equipment, which takes a long time. It is an object of the present invention to provide a printed circuit board cleaning liquid that can be omitted. The printed circuit board cleaning liquid of the present invention is 50 to 95% by weight.
of alcohol ether solvent and 5 to 50% by weight of water-soluble amine. The alcohol-ether solvent used in the printed circuit board cleaning solution according to the present invention permeates the board, and when washed with water, the purple discoloration can be removed together with the solvent. On the other hand, since the yellow (brown) color of the substrate occurs deeper inside the substrate than the purple discoloration, it cannot be removed solely by the permeability of the alcohol-ether solvent. Therefore, the yellow (brown) discoloration is removed by using a water-soluble amine or amide as an activator that reacts with the oxidized substrate material that is the yellow (brown) discoloration substance to neutralize it. be able to. Examples of alcohol ether solvents used in the present invention include ethylene glycol monobutyl ether, ethylene glycol isoamyl ether,
Examples include ethylene glycol monophenyl ether, diethyl cellosolve, cellosolve acetate, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and the like. Examples of water-soluble amines used in the present invention include diethylenetriamine, diethylamine, monoethanolamine, diethanolamine, triethanolamine, butylmonoethanolamine, cyclohexylamine, benzylamine, and phenylamine. According to the printed circuit board cleaning liquid of the present invention, purple discoloration can be prevented by immersing the board in the cleaning agent for 1 to 2 minutes at room temperature or by spraying the cleaning liquid onto the board, and yellow (brown) discoloration can be prevented by It is completely removed by soaking or spraying at 40°C for 1-2 minutes. The substrate that has been immersed or sprayed is then washed with water, and the cleaning effect will be even greater if the substrate is vibrated or the washing water is stirred during washing. The present invention will be explained in more detail with reference to the following examples. The cleaning solution according to the example was used in each cleaning step of the process of manufacturing a copper through-hole printed circuit board: Solder stripping solution treatment (immersion at 40°C for 3 minutes) Cleaning with the cleaning solution of Example 1――――――――→ (I) Solder leveler treatment (240℃, 5 seconds) Cleaning solution of Example 2――――――――→ Cleaning with () Gold plating treatment (55-60℃, 5 minutes immersion) Cleaning solution of Example 3― ――――――――→ Wash with () ^* Baking treatment (130℃, 2 hours) *Can be washed with water. Example 1 A cleaning solution having the following composition was prepared and cleaning was performed. Diethyl cellosolve 60% by weight Triethanolamine 40% by weight Example 2 A cleaning solution having the following composition was prepared and cleaning was performed. Cellosolve acetate 80% by weight Butylethanolamine 20% by weight Example 3 A cleaning solution having the following composition was prepared and cleaning was carried out (). Diethylene glycol 95% by weight Diethylamine 5% by weight Washing steps () () and () were carried out in Example 1,
When performed with cleaning solutions 2 and 3, the substrate did not undergo any discoloration, but when each cleaning step was performed with water alone, the substrate developed a significant discoloration of purple or yellow (brown). Further, no discoloration prevention effect was observed even when cleaning was performed using only either an alcohol ether solvent or an amine. Solder stripping treatment (immersion at 40°C for 3 minutes) Cleaning solution of Example 4――――――→ Gold plating treatment (immersion at 55 to 60°C for 5 minutes) Washing solution of Example 5―――――― ---→ Cleaning with () Solder fusing treatment (250°C, 5 seconds) ----→ Example of cleaning baking treatment with water 4 Cleaning was carried out by preparing a cleaning solution with the following composition. Ethylene glycol monobutyl ether
90% by weight Cyclohexylamine 10% by weight Example 5 A cleaning liquid having the following composition was prepared and cleaning was carried out (). Ethylene glycol monophenyl ether
85% by weight Phenylamine 15% by weight When cleaning steps () and () were performed with the cleaning solutions of Example 4 and Example 5, respectively, the substrate did not change color at all, but each cleaning step was performed with water only. In some cases, the substrate developed a significant discoloration of purple or yellow (brown). Furthermore, no discoloration prevention effect was observed even when cleaning was performed using only either an alcohol ether solvent or an amine. The electrical characteristics of the board cleaned with the printed circuit board cleaning solution of the present invention are extremely good, and the results of the insulation resistance test are as follows when compared with the board that was only washed with water.

【table】

[Table] From the above results, it can be seen that when cleaning () was performed using the cleaning solution of the present invention, a sufficient insulation resistance value was exhibited even immediately after cleaning, and flux components were sufficiently removed from the substrate. On the other hand, for those that have been washed with water, the resistance value decreases by heating and humidifying after washing.
It has changed by a factor of 10, indicating that washing has not been carried out sufficiently.

Claims (1)

[Claims] 1. Including gold plating process, solder removal process,
Consisting of 50 to 95% by weight alcohol ether solvent and 5 to 50% by weight water-soluble amine for use in cleaning before or after gold plating in printed circuit board manufacturing processes such as solder fusing processes. Printed circuit board cleaning liquid.