Causes of "dip plating" caused by chemical problems and improvement measures
When doing PCB pattern electroplating, PCB, FPC terminal surface treatments such as immersion gold, electro-gold, electro-tin, tin, etc. We often find that the finished board has a phenomenon of plating on the edge of the wet and dry film or the edge of the solder mask, or most of the boards appear, or some parts of the board appear. No matter which kind of situation will cause unnecessary scrap Or it will cause unnecessary trouble for the post-processing!
The reason is that we usually think of wet and dry film parameters and material performance problems; solder masks such as hard board inks and soft board cover films have problems, or problems have occurred in the printing, lamination, and curing stages. ． However, it was found that there were no problems or the problems were resolved in the above sections, and the phenomenon of infiltration will still occur. What else hasn't been found out?
The production of "plating" due to the problem of the chemical solution depends mainly on the pure tin finish formulation. The light penetrating ability is strong and the attack on the wet film during the electroplating process results in "plating". That is, "plating" occurs when pure tin finish is added too much or the current is slightly too large. Under normal current operation, the "plating" produced is related to the poor operating conditions of the potion. , High current, high stannous sulfate or high sulfur content, etc., these will accelerate the attack on the wet film.
2. Improvement countermeasures:
The performance of most pure tin finishes determines that they are more aggressive to wet films under the action of current. To avoid reducing the "penetration" of wet film pure tin plates, it is recommended that wet film pure tin plates be produced normally. Three points:
①. When adding pure tin varnish, it must be monitored in a small number of times. The content of pure tin varnish in the plating solution usually needs to control the lower limit;
② The current density is controlled within the allowable range;
③. Control of potion composition, such as stannous sulfate and sulfuric acid content in the lower limit will also be beneficial to improve "plating".
With the increasingly fierce competition in the circuit board industry, we need to improve our product yield by improving our processes to obtain profit growth points. High-quality pre-treatment potions will undoubtedly help us a lot at low cost.