PCB Solder Mask Colors

The Solder Mask is a thin protective polymer layer, which is applied on the conductive tracks of the printed circuit board during the manufacturing process. It protects the copper tracks from oxidation and helps avoiding short circuits. The color variation of the solder mask is the result of liquid photoimagible solder mask (LPI), a special ink, which can be screen printed, sprayed or coated on the PCB. 

A Green, Blue, Red or Yellow looking PCB is not actually ‘Green, Blue, Red or Yellow’ all the way through. It gets its color from the solder mask coating, which gives it a unique identity. For any PCB board, the solder mask color selection is crucial, as it helps for enhanced readability, clear visibility of the components mounted on the board, and contrast between tracks, vacant spaces & silkscreen printing / markings. 

The solder finish could be Glossy or Matte. A matte finish is slightly dull and soft. This means it will not reflect a lot of light directly but would look washed out under heavy light. PCBs with a Matte finish appear darker and don’t have a true shine, which makes them a good resort during fault detection. The glossy finish appears lighter in color and tends to reflect more light due to which they cannot be considered suitable for fault identification.

Generally, the thickness of the solder mask layer varies from 0.3 to 1.2 mils. Manufacturers offer PCBs with different solder mask colors to meet the variety of applications, even glossy and matte variants are also available.

Here are some popular colors of PCB Solder Masks:

Green: It is the most common and ideal solder mask color available for PCBs. It ensures good contrast and visibility between the components and the board surface. Quality inspection and fault detection become easier when the green solder mask is used.

Red: This color has a brilliant hue, with less contrast than green, but overall good contrast against traces, planes, and empty spaces. Flux residue can be removed easily when red solder resist is used.

Blue: This color provides a good contrast with silkscreen markings. It is generally used for the PCBs used in LCDs.

Black: This color looks good on the PCB, but cast a small shadow of the component, which makes it difficult to inspect.

White: It gives a unique visual appeal and highlights specific features of the PCB.

Yellow: It adds cleanliness, visibility, and style to the PCB. It offers a good contrast between empty spaces, traces, and planes. In place of white silkscreen, it is good to use black silkscreen, if yellow solder mask is used.

Purple: This color is one of the most expensive solder mask colors. It is basically used for PCBs of submarine equipment.