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Main factors affecting film thickness in OSP process of PCB surface treatment
Main factors affecting film thickness in OSP process of PCB surface treatment
The main factors affecting OSP film thickness are:
1. Concentration of main components of OSP: Alkyl benzimidazole or similar components (imidazoles) are the main components in the OSP solution, and its concentration is the fundamental factor determining the thickness of the OSP film.
2. Organic acids: The addition of organic acids can increase the solubility of alkyl benzimidazole in aqueous solutions. Promote the formation of complex protective films. However, if the amount is too much, the protective film deposited on the copper surface will be dissolved, so it is very important to control the addition value of organic acid (that is, PH value). When the pH value is too high, the solubility of the alkyl benzimidazole decreases, and an oily substance precipitates, which is not good for dip coating. If the PH value is controlled properly, a dense, uniform and moderately thick complex film can be obtained. When the pH value is too low, the complex film deposited on copper can be dissolved due to the increased solubility of the complex film, and a film with a desired thickness cannot be formed.
3. Dip coating time: Under the conditions of the determined OSP bath composition, temperature and pH value, the thickness of the complex protective film formation will start to rise linearly with the increase of the dip coating time, and then slowly as the time increases. The thickness of the film did not increase after a certain period of time.
4. Pre-preg: Pre-preg can prevent harmful ions such as chloride ions from damaging the OSP tank solution. In addition, there is a proper amount of copper ions in the prepreg solution (Hengqiao requires copper ions in the prepreg tank ≤10ppm), which can promote the formation of complex protective films and shorten the dip coating time. It is generally believed that, due to the presence of copper ions, alkyl benzimidazole and copper ions have been complexed to a certain extent in the pre-flux solution. When such a complex with a certain degree of aggregation is deposited on the copper surface to form a complex film, a thicker protective layer can be formed in a shorter time, thus acting as a complexation promoter. However, the content of alkyl benzimidazole or similar components (imidazoles) in the prepreg is extremely small. And when the copper ion is excessive, the prepreg solution will be prematurely aged and needs to be replaced.
The main role of the OSP prepreg tank is to accelerate the formation of OSP film thickness and deal with the effects of other harmful ions on the OSP tank. It is recommended to improve the performance of the potion and try not to use a prepreg tank as a routine process link. This can reduce costs.
Another point to tell you: the price of OSP's more than 1.2 yuan per square meter is very high, and the water is very large.
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