Introduction

Legend Print (also known as Silkscreen) is the process of applying text or patterns (including Images) on top of the Soldermask of a PCB.

The purpose is usually for the identification of components, component polarity, serial numbers, repair functionalities and logos etc., however, it may also be used to create visual effects such as pictures.

See also: Silkscreen and cure

Generating Legend Print Data

Provide a separate data file (see our PCB Design Guidelines – Input Data Formats) with an appropriate name (e.g. Top Legend) for each side of the PCB (Top/Bottom) that requires Legend Print.

If Native CAD data (Eagle BRD or KiCAD) is provided this should already contain the necessary data. Gerber X2 or a newer version of Gerber also clearly identifies the silkscreen layers.

IMPORTANT
  • Please ensure that you include the PCB Outline in your legend print data files. This is best drawn using a small line – e.g. 0.500mm wide where the center of the line is the exact board outline (it will be removed prior to production).

Design Rules for Legend Print

Legend print is designed to be printed on top of the Soldermask except for traditional single sided PCBs with through hole components where the legend is printed on the Top side of the PCB directly onto the laminate.

The copper pattern and soldermask are at the Bottom side of the PCB where the leads of the components are soldered.

IMPORTANT

We strongly advise to avoid legend being printed directly onto the:

  • Exposed copper or surface finished copper
  • Component pads
  • Any holes or cutouts
Text and Line Specifications


  • Minimum Legend Line Width: 0.10mm (4mil)
  • Minimum Text Height (for good readability): 1.00mm (39.5mil).


Legend Size

Minimum Clearances for PCB Manufacturing

The legend must have the following minimum clearances.

  • PCB edge:
    • 0.250mm for routing
    • 0.450mm for scoring
  • Exposed copper (or surface finished copper): 0.100mm
  • Holes and cutouts: 0.100mm


Minimum Clearances for PCB Assembly

The components to be placed by the Eurocircuits Assembly service must have the following minimum clearances to the Legend.

  • SMD component’s physical body: +0.200mm
  • SMD components with a pad pitch of ≤0.400mm: +2.00mm radius of each pad
  • SMD components with a pad size of <0.320mm: +2.00mm radius of each pad

Legend Clipping for PCB Manufacture

Introduction

Legend clipping is a pre-production process that clips parts or completely removes a specific legend object(s) based on predefined rules.

Eurocircuits defined rules are:

IMPORTANT
  • Whilst several rules are common to all manufacturers some may have additional rules for their individual process requirements.
  • We strongly recommend that you follow the rules for legend placement as defined by your EMS partner.

See also: PCB Assembly Guidelines – Legend Print Clipping

Legend Clipping Rules

These rules will apply to all PCBs manufactured by Eurocircuits, similar rules are used by most PCB manufacturers.

IMPORTANT
  • These rules do not remove legend, for example from beneath small components if they meet the minimum parameters above.
  • We strongly recommend that you follow the rules for legend placement as defined by your manufacturing partner if it is not Eurocircuits.
The Rules
  • – The corresponding exposed copper will be used as the reference layer along with the PCB outline and holes/cutouts.
  • – Any legend that does not meet the Minimum Clearances above will be clipped or completely removed to meet the minimum clearances.

    Legend Clipped
  • – Any legend line that is smaller than the Minimum Line Width as above will be removed.
IMPORTANT
  • In some cases, the clipping will result in the complete removal of a specific legend object
Approving the Legend Clipping

If you wish to check any Legend clipping before the manufacturing process starts please request a Pre-Production Approval (PPA) when you place the order.

The final production data can be then reviewed in the PCB Visualizer. The Compare Function of the visualizer will allow you to review and compare the original Legend data you uploaded with the production legend data.


Page Update History

27/02/2024 – Updated and reformated to include legend clearances for assembly

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