A via that connects the right two nets in an EDA tool may still use a layer span that the planned fabrication process does not support. Review allowed via types against the agreed construction before routing becomes dependent on them. Connectivity and manufacturability are separate checks.
Altium’s via-definition documentation separates layer-span definitions from diameter and hole-size properties. It also explains that possible spans depend on fabrication technology. A selectable layer pair is therefore not a supplier capability approval.
Create a manufacturing-based via table
List each approved type with its start and end layers, applicable board region, hole definition, pad requirements, and any relevant process note. Use unambiguous layer names that correspond to the fabrication stackup, particularly when internal layers have been added or renamed.
Ask the fabricator to review the complete combination of spans and construction. Do not qualify one via in isolation and assume that every combination of otherwise plausible vias can be built in the same board process.
Compare definitions with actual usage
| Audit item | Mismatch to detect |
|---|---|
| Allowed via-type list | Unused experimental or unapproved definitions remain available |
| Placed via inventory | A used span lacks a reviewed manufacturing definition |
| Board region | A via type is used in an inappropriate substack |
| Drill and drawing outputs | Layer-pair naming differs from the approved table |
Generate an inventory grouped by type and layer pair. Inspect outliers and manually edited vias, not only the default routing choice. A low count does not make an unapproved span harmless; a single occurrence can change the required process or make the design unacceptable. Include vias inside imported or reused layout blocks in the inventory, because their definitions may reflect a different historical stackup.
Recheck after stackup edits
- Preserve the previous approved via table.
- Review how added, deleted, or reordered layers affect each span.
- Inspect routing transitions that use the affected definitions.
- Confirm hole and pad rules remain appropriate.
- Regenerate and compare drill outputs.
Do not infer the intended manufacturing span from a visually correct two-dimensional connection. Review the layer properties of the placed object. In rigid-flex designs, verify the local stack region as well as the overall board layer list.
Close the audit with the used-via inventory and the supplier-reviewed construction. Keep any approved exceptions tied to specific locations or regions instead of a broad note permitting arbitrary blind or buried vias. The drill-table guide covers the complementary check of hole identity, plating, and output interpretation.
Move from reading to a build-ready project
Use the fabrication and assembly checklists to prepare drawings, production files and test requirements.
Open the DFM checklist