Solder mask covers selected outer-board areas while leaving required pads and contacts exposed. Its geometry must account for the manufacturing process and the assembly design. Color is only one specification; opening size, registration and the survival of narrow mask features matter more to the finished result.
Define the opening convention
Determine how the CAD system expresses mask openings and expansion. Review the exported mask artwork rather than relying on a screen color. For a pad near another exposed feature, consider the combined openings and the remaining mask between them.
Check narrow dams with the fabricator
A narrow mask strip between pads may not be reproducible with every process or registration condition. Confirm the proposed geometry for the actual board. If the strip cannot be maintained, review the resulting combined opening with the assembly team instead of accepting an undocumented change.
Specify via treatment deliberately
A via may be exposed, tented or treated by a separate plugging or filling process. These results are not interchangeable. If a via sits in a component pad, the required filling and surface condition must be defined explicitly; a mask instruction alone may not address solder wicking.
Keep paste and mask separate
Solder-mask artwork describes board coating. Paste artwork describes where the stencil deposits solder. A change to one does not automatically justify the same change to the other. Review both layers for fine-pitch and exposed-pad components before release.
Release checklist
- Inspect exported opening polarity and expansion.
- Confirm minimum reproducible mask features.
- Identify via-treatment exceptions in the drawing.
- Review paste apertures as a separate assembly decision.