● Mixture of two parts
● Shade difference
● Material color
● No clear color definition
● Differ from different manufacturers
Color differences could be caused by many things.
1) Since the solder mask is a mixture of two parts, having too much of one or the other can cause variance in color. There is never a 100% guarantee that the color will be the same every time.
2) There may be shade difference.
3) Material color could come in lighter of darker which could affect the look and color of the solder mask.
4) Most Customers has no clear mention of their requirement towards mask color in PCB Gerber / PCB drawing. That’s to say, the color is not clearly defined as light or dark in matte or semi gloss or gloss finish.
5) Solder mask colors may differ from different manufacturers or brands.
6) Copper from outer layers can cause color differences, if the outer layer have large copper plains they will look different in color than a board with outer layers that have less copper showing.
7) Hot air level machines have also been known to change the color of the mask due to the stress of the process.