Begin with an escape study, agree a manufacturable stackup, encode the rules, then complete layout and release verification.
What to consider
A useful checkpoint occurs before detailed routing: can the factory build the proposed via structures using stocked materials and provide the needed verification? A second checkpoint occurs before release: do the artwork, drill files, stackup and fabrication notes agree? The quotation should identify exceptions that change either cost or design assumptions.
A practical review example
Freeze the approved construction as a revision-controlled artifact. If material or via geometry changes after prototype, reopen the impedance, assembly and reliability reviews rather than carrying the old approval forward.
Checks before release
- Keep an explicit open-issues list.
- Separate planning assumptions from approved values.
- Update the production release after closing factory questions.
Connect this decision to fabrication
Use the stackup planner to organize the initial discussion. Keep proposed values separate from the approved drawing and document the effect of any change on the rest of the construction.
- Prove the package escape on a small routing study.
- Compare complete constructions using the same reliability requirements.
- Resolve the fabrication process before locking the layout.
Technical references
HDI construction types and definitionsHDI design and manufacturing overviewReferences checked 2 October 2026. Manufacturer data describes its stated construction and is not an HDIPCB.org manufacturing commitment.