PCB News - How to improve the chromatic aberration of the wet film and text on both sides of the PCB circuit board?

With the development of science and technology, people’s requirements for PCB quality are getting higher and higher. During production, there will always be such and other problems. We found that the green paint function not only prevents the circuit from oxidation and soldering short-circuits, but also other things. Influence? How to improve the chromatic aberration of the wet film and text on both sides of the PCB circuit board? How can the copper surface not be oxidized? The following will explain to you how to improve the chromatic aberration on both sides of the PCB circuit board wet film and text?

How to improve the chromatic aberration of the wet film and text on both sides of the PCB circuit board?

The main function of green paint is anti-oxidation and anti-welding. In addition, because it is also a dielectric material, it will still have a certain impact on impedance. The chromatic aberration problem 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 big difference in copper area, there is no way to change the actual state, and chromatic aberration will definitely exist. Therefore, the problem of chromatic aberration should focus on whether there are undesirable discoloration of ink, copper surface, and plate. Other problems should not be important issues of quality. Of course, some people simply use dark ink to hide the ugliness. As for the oxidation of the copper surface, the surface should be kept dry and maintained continuously after the pre-painting treatment and drying, especially the circuit boards should not be stacked together before they are actually dried. Because this kind of stack will make the residual hot water gas can not be eliminated, it will quickly affect the copper surface and cause oxidation.

The general method of making solder stop paint is to first coat the ink on one side and then pre-dry, and then coat the second side. 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 darken a bit. This kind of problem seems to be difficult to avoid if the existing PCB manufacturing process is used. Therefore, some manufacturers will separate the two sides of the circuit board, do one side of the coating, pre-bake, exposure, development, hardening, and then do a pre-treatment, so that the other side of the copper also appears fresh copper surface, and then do the whole Process. Although this approach can improve the color of the copper surface, it has a negative impact on the size control, exposure alignment, flatness of the board, and processing costs, so it is not practical.

At present, many circuit board manufacturers have begun to use solder resist spray treatment, which can reduce the risk of color difference between two bakings. As for the problems that cannot be overcome in practice, it is recommended to discuss the actual functional problems with the customer. As long as there is no problem with the function, the color difference should not be the main consideration for quality.