HDI fabrication builds the intended interconnect structure through a controlled sequence of imaging, lamination, drilling, metallization and inspection.
What to consider
The sequence depends on the core and via architecture. Internal connections must be completed while the relevant subassembly is accessible. Build-up layers then add dielectric and copper, followed by the required via formation and processing. Outer circuitry, solder mask, surface finish and test complete the board. The factory’s traveler, not a generic process diagram, defines the actual sequence.
A practical review example
A 2+4+2 construction typically needs successive build-up operations around its core. Ask the supplier to identify the core process, each via span, any filling step and the inspection point before the structure is covered.
Checks before release
- Approve a cross-section and sequence before tooling.
- Identify any added sublamination or filling operation.
- Ensure inspection access exists at the required stages.
Connect this decision to fabrication
Use the lamination guide 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.
- Ask the fabricator to confirm the complete construction in writing.
- Resolve manufacturing exceptions before tooling.
- Retain the approved drawing, stackup and inspection plan with the release.
Technical references
Fabrication design guidelinesConstruction-specific HDI capabilities and FAQReferences checked 2 October 2026. Manufacturer data describes its stated construction and is not an HDIPCB.org manufacturing commitment.