Identify what is actually skipped

Name the entry layer, intermediate layer, and target layer. Show the dielectric regions and copper conditions along the entire opening. Confirm whether the intermediate layer is intentionally unconnected and how its clearance is maintained.

Altium's via guide describes skip microvias as a possible two-layer span where the dielectric construction permits it. Do not interpret CAD support for that span as approval for an arbitrary stack thickness or material combination.

Compare the depth with alternatives

For an illustrative transition from L1 to L3, compare a supported skip structure with two sequential L1–L2 and L2–L3 microvias. The skip option changes depth and landing requirements; the two-via option introduces an intermediate interface and either a stacked or offset arrangement.

Use actual proposed dimensions and agreed measurement conventions to compare aspect ratio. A visually shorter chain in a drawing may create a deeper individual opening, so count physical depth rather than symbols.

Review intermediate copper deliberately

The bypassed layer may carry a reference plane, power region, or routed signals. Check its clearance to the opening and the impact on neighboring copper. If it is a reference plane, evaluate how the transition and associated clearances affect the signal's return path.

  • Confirm the allowed material and dielectric construction.
  • Record entry, intermediate clearance, and target geometry.
  • Check registration to all relevant copper layers.
  • Obtain approval for the complete skip structure before routing broadly.

Keep usage easy to audit

Assign skip structures a distinct via type and drill-pair identity in the CAD data. Inspect their locations after interactive routing or importing older design fragments. If only a small number are needed, identify those sites explicitly so the fabricator can review the demanding features without searching the entire artwork.

DESIGN NOTE / SCHEMATIC

Adjacent-layer access, one connection at a time

Signal copper

Dielectric · geometry + material

Reference copper

Core or build-up dielectric

Signal copper

Illustrative only. Copper thickness, dielectric construction and via spans require a reviewed stackup.

Common questions

Does a skip via always reduce manufacturing complexity?

No. It removes one kind of intermediate connection while imposing different drilling and geometry requirements. Compare the complete approved processes.

Can I replace two microvias with a skip via late in layout?

Only after reviewing the revised structure, clearances, reference path, and manufacturing sequence. Matching net endpoints is not enough.

References & further reading

Method & assumptions · General design guidance. Validate the proposed construction and acceptance criteria for your project.