IPC construction types and 1+N+1 notation describe different aspects of a board. Do not read Type II as an automatic synonym for 2+N+2.
What to consider
Construction type identifies an interconnection arrangement; build-up notation counts layers added around a core. A drawing should show via spans explicitly so a supplier does not have to infer them from a shorthand label. When a specification invokes an IPC document, use the required revision and the agreed acceptance requirements.
A practical review example
A 1+6+1 drawing has eight copper layers. Whether it uses buried core interconnects is an additional choice. Write both the eight-layer allocation and the hole spans rather than relying on a type label.
Checks before release
- List core through connections separately from outer microvias.
- Check the customer specification for the applicable standard revision.
- Ask for a cross-section sketch in the proposed stackup.
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.