PCB Design Guidelines-Legend Print

Legend Print (also known as Silkscreen) is process of applying text or patterns on top of the Soldermask.The purpose is usually for the identification of components, component polarity, serial numbers and logos.However, it may also be used to create visual effects such as pictures.

Specifications for Legend Print
*Minimum Legend Line Width: 0.10mm (4mil)
*Minimum Text height for good readability: 1.00mm (39.5mil).

Legend Clipping
We will always clip the Legend Print against the corresponding Soldermask layer to ensure no legend is printed on component pads.

Clipping Rules
*Legend clipping clearance is 0.100mm (4mil) back from the Soldermask openings.
*Any parts of line smaller than 0.100mm (4mil) will be removed.

In absence of a Soldermask layer, the legend print will be clipped against the corresponding copper layer.If there is no copper layer, the legend will be clipped against the drill layer.

DESIGN TIP
To avoid your legend being clipped maintain a minimum distance of 0.200mm (8mil) between your legend elements and the copper pattern.The 0.200mm (8mil) = 0.100mm (4mil) Soldermask Annular Ring + 0.100mm (4mil) Legend Clipping Clearance.

Readability
It is important to ensure that all legend text is correctly readable.
As a PCB is always viewed from top to bottom through the PCB, text on the top layer of your board should be readable and text on the bottom layer should be non-readable or mirrored.

Board Outline
Please always include the board outline in your legend layers output data as this helps avoid any potential misalignment, mirroring or rotation issues.
This is best done using a small line – e.g. 0.500mm (20mil) wide – where the center of the line is the exact board outline.We will remove this line in the actual production data we use for manufacturing your boards.In all cases we will clip away any legend text within 0.200mm (10mil) of the board edge.

Important
We strongly advise NOT to place a legend layer on the copper layer side of a PCB without a Soldermask layer.

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