PCB Stencil Alignment: Single Board or Panel?

A stencil made from a correct single-board paste layer can still be wrong for an assembly process that prints a complete panel. Before ordering, decide what the printer will hold and which paste pattern it must reproduce. Match the stencil to that physical arrangement.

Identify the printing unit

State whether you will print one board at a time or an array. For a panel, include the complete approved panel drawing and the matching paste data. Record the number of boards, spacing, rotation and rail arrangement. A repeated design in the PCB file does not tell the stencil supplier which file you intend to use.

For example, rotating every second board in an array changes the required aperture arrangement. Repeating a single-board paste pattern without the rotation would not reproduce that panel. Review the full print area rather than only one familiar footprint.

Confirm side and view conventions

Identify top, bottom or both, based on the actual assembly plan. Use clearly named paste outputs and an assembly view. Do not rename a solder-mask file as a paste file when the required export is missing; return to the CAD project and generate the correct output.

If two stencils are required, give each an explicit side and revision. Confirm any supplier-specific viewing convention instead of manually mirroring artwork based on its appearance in an unfamiliar viewer.

Match the physical printing setup

Provide the frame or frameless requirement and the printer or holder constraints. Ask the assembler to specify the appropriate stencil construction and aperture review for the component mix. A common foil thickness is not automatically suitable for every fine-pitch, exposed-pad or mixed-size assembly.

• Confirm the intended single-board or panel footprint.
• Compare paste data with the final copper-pad locations.
• Identify the populated side and excluded areas.
• State frame, usable area and registration requirements.
• Agree who approves any aperture modifications.

Recheck after panel changes

Treat a change in array spacing, rails or orientation as a reason to review the stencil. Keep the panel and stencil identifiers together in the release record. Before production, compare a representative corner, central footprint and alignment feature against the approved drawing. If something does not line up, resolve the file or setup discrepancy before printing paste onto a batch of boards.