Route a differential pair with controlled geometry and a consistent environment. Length matching does not compensate for a broken return path or a poorly designed transition.
What to consider
Keep breakout asymmetry and unequal via transitions under review. Avoid unnecessary tight meanders that increase coupling between adjacent route segments. The required impedance and skew depend on the interface and device guidance. Treat package and connector contributions as part of the channel where relevant.
A practical review example
A pair with identical board lengths can still have skew from package escape and different transition geometries. Compare the complete paths before adding serpentine length.
Checks before release
- Use interface-specific impedance and skew constraints.
- Review pair symmetry at pads and vias.
- Keep adequate spacing from unrelated aggressors.
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.