How to Include Fiducial Marks on an SMT Stencil?

What Are Fiducial Marks?

Fiducial marks are reference points used during SMT assembly to ensure accurate positioning of the PCB for solder paste printing and component placement. They allow automated equipment to precisely locate and align the PCB, helping improve overall assembly accuracy.

On a PCB, a fiducial mark is typically a small, circular copper pad with solder mask clearance, located in a consistent position near the board edge. If stencil fiducials are required, we recommend specifying their locations in the paste layer of the stencil file.

Do You Need Fiducial Marks?

Whether fiducial marks are needed depends on your SMT assembly process and equipment.

• Fully automatic SMT printing: Fiducials are generally recommended for accurate machine alignment.
• Semi-automatic printing: Fiducials may be recommended depending on the equipment and alignment method.
• Manual printing: Fiducials are generally not required.

Fiducial Mark Options

When ordering an SMT stencil, you can choose one of the following fiducial mark options:

1Etched Half

A half-etched fiducial is partially etched into the stencil material, creating a shallow reference feature without producing a complete opening. By default, the fiducial would be half-etched on the bottom side of the stencil.

This option is recommended for applications where the stencil is aligned using automated equipment, subject to the requirements of the specific printer.

2Etched Through

A through-etched fiducial is etched completely through the stencil material, creating a full opening.

This option may be suitable for manual or semi-automatic alignment, depending on the stencil design and printing equipment.

3No Fiducial

Select No Fiducial if stencil fiducials are not required for your assembly process.

Important Notes

• If you require stencil fiducials, select Etched Half or Etched Through when placing your order. Make sure the fiducial locations are included in the paste layer of the stencil file.
• If the fiducial information in your file does not match the selected stencil option, the fiducials will not be manufactured as requested.
• Although stencil fiducial locations are included in the paste layer as required, they are not treated as standard solder paste apertures during stencil manufacturing.
• For most fully automatic SMT printing applications, Etched Half is generally the recommended option, subject to the requirements of the printer and assembly process.