What is a solder mask? Solder masks is a very important part of protecting a PCB. Solder mask, or solder resister is a thin covering that protects the PCB from oxidation.
It also prevents solder bridges from forming between solder pads that are close together. There are other ways how solder masks can be used effectively by companies. One example lies with how solder masks are traditionally green, but now available in different colors. Different colors can be used to tell apart revisions easier.
If you make your revision one board green but your revision two board white, you can tell the difference just by looking at it. The color of the solder masks has no effect on the performance of the PCB itself. However, the difference between the colors is the resolution of the board will be different. Colors like red and blue match the iconic green PCB in resolution. Black and yellow solder masks however have significantly less resolution than green and the clear solder masks has greater resolutions.
There are many theories why solder masks were originally green. One of the reasons was because when the solder mask was first produced, the base resin was a brownish yellow and the hardener was a muddy brown. When you combined these two components to form the solder mask, it turned green. Another theory was because the color green has been proven by many scientists that the color is the most visible and noticeable to the human eye. Colors are just different wavelengths and yellow and green are the wavelengths that are most easily noticeable under normal light. The color green is the easiest to see, and also easy on the eyes so they won’t tire the human out. This helpful factor helps out assemblers and quality control inspectors so maybe that is why green is the iconic color that the image of a PCB has come to accept.