Fine traces and clearances are fabrication-dependent geometry choices. They should be sized with copper thickness, impedance, current and yield in view.
What to consider
Starting copper and finished plated copper affect achievable conductor shape. A factory’s minimum may apply to a particular layer, copper weight or production tier. Use larger features where routing permits and reserve the tightest geometry for constrained regions. Current-carrying nets require separate thermal and voltage-drop analysis.
A practical review example
A short neck-down under a BGA and a long narrow supply route are different design cases. The first may be an escape compromise; the second can create unacceptable resistance and heating.
Checks before release
- Specify layer-specific copper and tolerances.
- Check minimum finished conductor dimensions.
- Review current and impedance requirements separately.
Connect this decision to fabrication
Use the design checklist 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.
- Use rules confirmed for the chosen factory and construction.
- Inspect return paths through every critical breakout.
- Release consistent artwork, drills, stackup and drawing revisions.
Technical references
HDI design and manufacturing overviewFabrication design guidelinesReferences checked 2 October 2026. Manufacturer data describes its stated construction and is not an HDIPCB.org manufacturing commitment.