It is a good method to prepare etching solution with 30% hydrogen peroxide and industrial hydrochloric acid in the ratio of 1:3. However, the matters needing attention and methods in the production are not explained in detail. The following is a supplementary explanation based on practical experience.
1、 Matters needing attention
① In this method, a small amount of chlorine is released in the process of corrosion reaction. The operation should be carried out in a ventilated place. The operator had better stand at the upper air outlet to avoid chlorine poisoning.
② This kind of corrosion solution has fast reaction speed, so it should be prepared in strict accordance with the proportion and operation method. If the proportion is too improper, it will cause boiling, liquid water spilling out of the plate, causing accidents.
③ It’s better to use a glass plate filled with corrosive solution for corrosion, so as to observe the corrosion condition at any time.
2、 Preparation method of corrosive solution
The industrial hydrogen peroxide (hydrogen peroxide) with the concentration of 31qo was mixed with 37% hydrochloric acid and water in the ratio of 1:3:4. During the operation, four parts of water should be poured into the plate first, then three parts of hydrochloric acid should be poured into the plate, and then a part of hydrogen peroxide should be added slowly after being evenly stirred with the glass rod, and then the printed copper foil can be put into the corrosive solution after being evenly stirred with the glass rod, and the corrosion can be completed in about five minutes. Take out the corroded copper foil and immediately put it into clean water to wash and dry it before use. The circuit board can be shaken to accelerate the corrosion process.
3、 Concentration adjustment of hydrogen peroxide and hydrochloric acid
The concentration of products purchased in chemical stores is mostly higher than the required concentration, which is not suitable for direct use. So how to dilute? The solution dilution mouth sum is calculated as follows: divide the difference between large and small molecules by small molecules, and then multiply the amount of solution to get the amount of water to be added. For example, if the existing concentration of 85% hydrochloric acid solution is 500ml, how many ml of water should be added to release it to 37%? The method is as follows
The difference between large and small molecules is 85-37 = 48; divided by small molecules is 48 △ 37 ≈ 1.3; to multiply the solution volume by 1.3 × 500 = 650ml, 650ml of water is needed. After the required concentration is prepared, it can be prepared according to the above proportion.
Compared with ferric chloride, this method has the advantages of fast corrosion, low cost and simple operation. It is especially suitable for making large area printed circuit board. Even if the first time using this method to make personnel as long as the operation requirements can also make beautiful circuit board.
