A 0.4 mm pitch BGA often makes conventional escape difficult, but the correct via structure depends on land size, pin assignment and available routing layers.
What to consider
Test whether a trace can pass between the actual lands with the factory’s finished conductor and clearance requirements. Via-in-pad may be useful, yet it introduces filling and assembly requirements. Select the number of build-ups from the escape study, not from a pitch-to-order chart presented as a universal rule.
A practical review example
If the pad diameter is 0.22 mm, adjacent pad edges are nominally 0.18 mm apart on a square 0.4 mm grid. A 0.06 mm trace with 0.06 mm clearance on both sides exactly consumes that nominal gap and leaves no extra geometric margin. Manufacturing tolerances and the final land definition still govern feasibility.
Checks before release
- Review the package manufacturer’s land pattern.
- Test edge-to-edge channel dimensions.
- Confirm solder-mask and filling capability.
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.