Any-layer HDI offers interconnection through successive microvia structures throughout the board. The name does not remove physical or qualification limits.
What to consider
A route may reach many layer combinations through a sequence of adjacent connections, but that is different from drilling one laser hole through an arbitrary stack thickness. The chosen process controls what can be stacked, filled and reliably connected. Reserve adequate plane copper and avoid treating every layer as unrestricted routing space.
A practical review example
Create a via-span matrix for the candidate construction. For each required connection, show the adjacent-layer transitions and the test structure that represents the longest or most demanding stack.
Checks before release
- Ask which layer combinations are actually supported.
- Review stacked-interface qualification.
- Compare with a lower-order design on the same outline.
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.
- Give every signal layer a defined return-path strategy.
- Review material and copper balance about the board center.
- Specify every via span and the factory-approved lamination sequence.
Technical references
HDI construction types and definitionsFabrication design guidelinesReferences checked 2 October 2026. Manufacturer data describes its stated construction and is not an HDIPCB.org manufacturing commitment.