An RF route needs a controlled transition from component pad through vias, planes and connectors. A short microvia is helpful only within a suitable surrounding geometry.
What to consider
Pad capacitance, ground-via arrangement, reference openings and dielectric changes can dominate a transition. Hybrid materials add construction choices that influence phase and loss. Model the full transition where the frequency and bandwidth require it, and correlate with a suitable test structure.
A practical review example
Compare the proposed pad/via launch with the device or connector reference design, then adapt it to the actual stackup using electromagnetic analysis. Do not copy dimensions across different dielectric thicknesses.
Checks before release
- Control reference and ground connections around the launch.
- Use the actual stackup in the model.
- Define the verification coupon and measurement reference planes.
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.