HDI design guidelines should turn product requirements into a construction that a selected fabricator can reproduce. Begin with device escape, electrical references and mechanical limits, then establish the rules for traces, pads and interconnections. Generic minimum dimensions are poor substitutes for an approved stackup and process-specific design rules.
Work from the most constrained region
Create a representative escape layout for the densest package before routing the full board. Use its actual pin assignment and land pattern. Check where signals, power and ground must go, and reserve space for the reference structures they need. This early exercise reveals whether the proposed layer access is useful.
Then expand the review to connectors, mounting features, shields and assembly access. A design that routes under the main BGA can still fail at the connector field or interfere with a fixture. Place test access while the architecture is flexible.
Rules to agree with the fabricator
| Rule group | Items to document |
|---|---|
| Copper geometry | Finished trace width, spacing, copper thickness and permitted local neck-downs |
| Interconnections | Allowed spans, pad sizes, registration allowances and fill requirements |
| Materials | Named construction, thickness tolerances and substitution approval |
| Electrical targets | Reference planes, impedance definitions and verification method |
Keep the rules internally consistent
Changing dielectric thickness to improve manufacturability can also change impedance and via geometry. Changing the via pad can reduce an escape channel. Review these interactions as one construction change rather than as independent edits in separate documents.
Do not assume that an online calculator has approved the design. Use estimates to explore alternatives, then reconcile the selected geometry with the fabricator's finished values and an appropriate electrical model. Record who may adjust trace widths during CAM and what changes require engineering approval.
Release and learn
Run the released netlist against the manufacturing data, verify layer naming and check that the drill table matches the actual files. Resolve each DFM comment with an owner and a written disposition. A comment marked “accepted” should identify the exact drawing or data revision that implements it.
For the first build, identify what will be learned about routing, fabrication, assembly and test. Preserve failures and approved deviations with the final configuration. When moving to volume or another supplier, compare that configuration rather than assuming the same Gerber filename means the same manufactured product. These guidelines are planning recommendations, not a claim that every listed feature is available from this website's operator.
Continue the engineering review
- Fine-pitch BGA fanout with microvias
- HDI PCB stackup selection
- HDI DFM release checklist
- HDI PCB engineering hub
Review your HDI requirements
Share the board revision, proposed stackup, quantity and open questions. Include the requirements discussed in this guide so the project review starts with the same assumptions.