PCB Fabrication

Teach you how to deal with some defects that affect film thickness in the OSP process reasonably

by:A-TECH      2021-03-22
In PCB proofing, the OSP process is very important. Here are some examples of how the OSP process in PCB proofing affects the film thickness: 1. Dip coating time: in the OSP bath composition, temperature and PH value conditions Under certain circumstances, the thickness of the complex protective film will start to rise linearly with the increase of dipping time, and then slowly progress with the extension of time. After a certain period of time, the thickness of the film is basically invisible There is an increase. 2. Pre-soaking: Pre-soaking can prevent harmful ions such as chloride ions from damaging the OSP tank solution. Moreover, there is an appropriate amount of copper ions in the prepreg solution (Hengqiao requires prepreg copper ions ≤ 10ppm), which can promote the formation of complex protective film and shorten the dip coating time. It is generally believed that due to the presence of copper ions, the alkylbenzimidazole and copper ions have been complexed to a certain extent in the pre-flux solution. When this kind of 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 short time, thus acting as a complexing accelerator. However, the content of alkylbenzimidazole or similar components (imidazoles) in the prepreg is very small. In addition, when copper ions are excessive, the prepreg solution will age prematurely and need to be replaced. The main function of the OSP prepreg tank is to accelerate the formation of the OSP film thickness and deal with the impact of other harmful ions on the OSP tank. It is recommended to improve the performance of the syrup and try not to use the prepreg tank as a routine process link, so as to reduce costs. 3. The concentration of the main components of OSP: Alkylbenzimidazole or similar components (imidazoles) are the main components in the OSP liquid. The concentration is the most fundamental issue that determines the thickness of the OSP. 4. Organic acid: The addition of organic acid can increase the solubility of alkylbenzimidazole in aqueous solution. Promote the formation of complex protective film. However, if the amount is too much, it will dissolve the protective film deposited on the copper surface, so it is very important to control the added value of organic acid (ie PH value). When the PH value is too high, the solubility of alkylbenzimidazole will decrease, and oily matter will precipitate, which is not good for dipping. With reasonable pH control, a dense, uniform, and moderately thick complex film can be obtained. If the PH value is too low, the solubility of the complex film will increase, so that the complex deposited on the copper can be dissolved and the film with the required thickness cannot be formed.
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