Main factors affecting film thickness in PCB surface treatment OSP process

Main factors affecting film thickness in PCB surface treatment OSP process

The main factors affecting the thickness of OSP film are:

1. The main component concentration of OSP: alkylbenzimidazole or similar components (imidazoles) are the main components in the OSP solution, and the concentration is the basis for determining the thickness of the OSP film.

2. Organic acids: The addition of organic acids can increase the solubility of alkylbenzimidazoles in aqueous solution. Promotes the formation of a complex protective film. Too much use will dissolve the protective film deposited on the copper surface, so controlling the addition value (ie, pH) of the organic acid is critical. When the pH is too high, the solubility of the alkylbenzimidazole is lowered, and an oily substance is precipitated, which is disadvantageous for dip coating. A well-densified, uniform, and moderately complex complex membrane can be obtained with reasonable pH control. On the other hand, if the pH is too low, the solubility of the complex film increases, and the complex deposited on the copper can be dissolved to form a film of a desired thickness.

3. Dip coating time: Under the determined composition, temperature and pH of the OSP bath, the thickness of the complex protective film begins to rise linearly with the dip coating time, and then slowly with time. After the lapse of a certain period of time, the film thickness did not substantially increase.

4. Prepreg: Prepreg can prevent harmful ions such as chloride ions from damaging the OSP cylinder solution. Moreover, there is an appropriate amount of copper ions in the prepreg solution (Hybridge requires copper ions of the prepreg cylinder ≤ 10 ppm), which can promote the formation of the complex protective film and shorten the dip coating time. It is believed that alkyl benzimidazole has a certain degree of complexation with copper ions in the preflux solution due to the presence of copper ions. When such a complex aggregated to a copper surface forms a complex film, a thick protective layer can be formed in a short period of time, thereby functioning as a complexing accelerator. However, the content of alkylbenzimidazole or the like (imidazole) in the prepreg is extremely small. When the copper ions are excessive, the prepreg solution will age prematurely and needs to be replaced.

The main function of the OSP prepreg cylinder is to accelerate the formation of OSP film thickness and to treat the effects of other harmful ions on the OSP cylinder. It is recommended that the performance of the syrup is good. Try not to use the pre-dip tank as a routine process. This can reduce the cost.

In addition, I would like to tell you that the price of the syrup that costs more than 1.2 yuan per square meter of OSP is extremely high and the water is very high.