How to improve the color difference between the two sides of the wet film and text on the PCB circuit board?

How to improve the color difference between the two sides of the wet film and text on the PCB circuit board?

 In addition to the green paint function to prevent the circuit from oxidation and soldering short circuit, what other effects? How to improve the color difference between the two sides of the wet film and text on the PCB circuit board? How can we prevent the copper surface from oxidation?

   The main function of green paint is anti-oxidation and welding. In addition, because it is also a dielectric material, it still has a certain impact on impedance. The problem of chromatic aberration of the circuit board is difficult to solve, especially when the copper area of the board surface is different. Because of the color difference, it often comes from the color reflection state of the circuit board surface. If there is a large difference in copper area, there is no way to change the actual state, the color difference will definitely exist. Therefore, the problems of color difference should focus on whether there should be discoloration of ink, copper surface, and plate that should not occur. Other problems should not be important issues of quality. Of course, some people simply use dark ink, which can hide the ugliness. As for the oxidation of the copper surface, the surface should be kept dry and maintained after drying before coating, especially not stacked together before the circuit boards are actually dried. Because this kind of stack makes the residual hot water gas unable to be eliminated, it will soon affect the copper surface and cause oxidation.

  In general, the manufacturing method of the solder stop paint is to firstly apply ink on one side and then pre-bake, and then perform the second side coating. If the drying time is not very long, the color of the copper surface will not change much. But more or less, the surface color will definitely be a little darker. This problem seems to be difficult to avoid using existing processes. Therefore, some manufacturers work separately on both sides of the circuit board, first coating, pre-baking, exposing, developing, and hardening one side, and then performing a pre-treatment after that, so that the copper on the other side also presents a fresh copper surface, and then the whole is made again Process. This method can certainly improve the color of the copper surface, but the size control, exposure alignment, board surface flatness, and processing costs