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Silk Screen (SS) on PCBs: Purpose, Best Practices & Inspection​

Discover why Silk Screen (SS) marking is critical for PCB assembly, maintenance, and compliance—plus when, where, and how to apply it for maximum benefit and clarity.​​

electronics and mechanical design intro image: a PCB is being assembled as 6-building-blocks, a hand comes with th last block.

Why Use Silk Screen (SS) on PCBs?

Assembly & Repair:

Helps personnel recognize components, orientation, board name, revision, part number, and process type (RoHS/SnPb).

Dense Boards:

Not all components may be labeled—mark only key components. Consider library parts without default markings for dense layouts.

Compliance & Identification:

Used by authorities to identify registration numbers, standards, company details, and RoHS compliance.

Hazard & Function:

Clearly display high voltage, dip switch position, voltage, function, or waveform at special points.

Field Maintenance:

Assists with recognizing key components, hazard markings, and board details during installation or troubleshooting.

How Silk Screen Looks on a PCB

Standard SS Marking

Adds a secondary pad at the trace-pad junction.
The smaller pad is offset a few mils from the main pad center, creating a “snowman” look.

Standard Silk Screen Marking

SS Marked in Green

Adds gradual traces from the pad towards the trace.—this is the most common teardrop style.

Silk Screen Marked in Green

Where to Apply Silk Screen Markings

  • Polarity markers for capacitors, diodes, LEDs, and ICs.
  • Major components (ICs and large parts).
  • PCB marking: name, revision, part number, and serial/barcode labels.
  • Hazard indicators, voltage/waveform/function at special points.
  • Connector and screw positions for easier assembly inspection.

How to Use Silk Screen (SS) on PCBs?

Last Stage:

Most CAD tools add SS automatically as the last design stage—final review is essential to relocate, remove, or adjust markings.

Solder Barrier:

SS is sometimes used to prevent solder shorts or as a background for better identifying missing components — common in low-cost devices.

Special Markings:

Add special markings for RoHS status, company name, website, logo, dip switch explanation, voltage/signal names, and date code.

Dense Boards:

Only mark essential components to avoid clutter. Consider building part libraries to exclude unnecessary SS.

Position:

Mark positions for labels (serial number, barcode) and PCB manufacturer date codes.

How Should A Silk Screen Look?

  • Line width: 6mil minimum (5mil possible at extra cost).
  • String height: 30mil minimum for readability.
  • Distance to copper: 5mil minimum; less may be clipped by manufacturer.
  • Font: Use simple, clean fonts for maximum clarity.
  • Manufacturers automatically clip SS over pads, test points, and vias.
Before Manufacturer Clipping
Silk Screen Before Manufacturer Clipping
After Manufacturer Clipping
Silk Screen After Manufacturer Clipping

Silk Screen & Manufacturing Inspection

  • SS over SMT pad / PTH / NPTH
  • SS over FM (Fiducial Mark) or TP (Test Point)
  • Mismatched SS to reference designator
  • Missing polarity marker
  • Insufficient clearance to copper, route, or part
  • Small font or line width
  • Overlapping or multiple reference designators
  • Overlapping strings
  • Missing SS or unreadable strings

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