At 0.5 mm pitch, compare dog-bone escape, via-in-pad and a mixed approach using actual finished geometry.
What to consider
A board may need HDI for some package rows while keeping more conventional routing elsewhere. Regional rules can control finer geometry under the BGA without applying the minimum line/space across the whole board. Check that escape transitions do not sever the ground reference needed by the outgoing channels.
A practical review example
Evaluate a surface escape for outer signal rows and short blind transitions for inner rows. If a second build-up is proposed, show which otherwise blocked nets require it.
Checks before release
- Use local rather than unnecessary global fine rules.
- Check power connectivity and current paths.
- Compare the full fabrication cost of each escape option.
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.