Edge rate helps determine whether interconnect behavior needs transmission-line treatment. Clock frequency alone can hide a fast-edge routing problem.
What to consider
A simple first screen compares flight time against rise time. The online checker estimates delay using effective dielectric constant and route length. Its threshold is deliberately a screening heuristic; it cannot validate termination, impedance, connector behavior or a full interface channel.
A practical review example
A 30 mm route with effective dielectric constant 3.5 has approximately 187 ps one-way flight time. With a 200 ps edge, this is not an electrically negligible interconnect and deserves transmission-line review.
Checks before release
- Use the device’s relevant rise/fall time.
- Include package and connector effects when necessary.
- Follow the interface and device termination guidance.
Connect this decision to fabrication
Use the signal routing 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 edge rate and channel loss, not clock frequency alone.
- Keep a continuous return path at traces, vias and connectors.
- Verify final geometry against the device and interface requirements.
Technical references
HDI design and manufacturing overviewReferences checked 2 October 2026. Manufacturer data describes its stated construction and is not an HDIPCB.org manufacturing commitment.