The ink composition is how to adjust, why oil resistance welding coating is very beautiful, white and black oil?

Now we encounter a tricky question, with a hard board need to be printed black solder resist ink, found that when using the traditional screen printing technology printing ink cannot be completely 100% to block a hole (the thickness is 0.4 mm, hole diameter is 0.2 mm), and the ink thickness and evenness in terms of how the effect is not ideal; Later advice with new printing roller coating technology, the first sample with silk screen roll coater coating of white LED aluminum plate white ink effect is very ideal, various aspects are beyond the traditional screen printing effect, but the sample again when using black ink printing roll coater coating can't cover the copper foil (because the terminal customers require the use of black resistance welding), ink block probability is very poor, copper surface cover rate is only about 50%; We analyze partial thin ink or ink concentration is low and then again to adjust parameters, such as sample results effect is the same, black ink sample of using original sun brand, brand new Korea and ink slab are tried to the result. We still want to adopt the way of printing roll coater coating, after all, to effect and stability of the machine were all better than artificial silk screen control, so ask ace to help analyze the technology, the ink composition is how to adjust, why oil resistance welding coating is very beautiful, white and black oil?