Does the color of a circuit board’s solder mask matter? If you’ve ever cracked open a computer, you’re probably well aware that green is the universal color that most manufacturers abide by. However, over the past few years, this standard has evolved to encompass beyond the standard green.

Why is this the case? Is one color preferable over another? In this blog, FPC supplier examine why solder mask color matters, when it doesn’t, and the best options for both manufacturers and consumers.

The color that you see on a printed circuit board procuuced by FPC supplier is referred to as its solder mask, solder resist, or solder stop mask. A solder mask is a thin layer of polymer that protects the copper traces printed onto the board from oxidation, as well as preventing solder bridges (unintentional connections between two conductors.

After a solder mask is applied, openings must be made by a process called photolithography. Photolithography uses a photosensitive chemical photoresist to transfer geometric patterns onto the wafer. This creates the characteristic patterns commonly seen on a printed circuit board. For the purposes of electronic design automation, the solder mask is treated as an additional layer of the circuit board, and is described as a Gerber file similar to that of copper and silkscreen layers.

From the perspective of circuit board functionality, solder mask color rarely makes a difference. Its primary function is as an added layer of protection. However, the color selected for a PCB is critical for the purposes of defect inspection. Colors with the highest contrast like green are generally preferred as they offer the greatest trace visibility, which is particularly important during PCB prototyping and testing.