Separate location from process

A blind connection may use a microvia process or another supported construction. A connection that is exposed during an intermediate build stage may be buried in the final board. Therefore, an order note that says only 'blind and buried vias' leaves key technical decisions unresolved.

Label each via with start and end layers, a structure identifier, and dimensional requirements. Add the required fill or surface condition independently. This prevents the same name from being interpreted differently by layout, purchasing, and fabrication teams.

Use access to recover routing space

A through via occupies geometry across the stack, even where the net does not need a connection. Restricting a via span can release space on other layers, but only if the required restricted span is practical to manufacture.

For an illustrative dense module, moving a local surface-to-inner connection to an approved blind structure may clear deeper routing channels. Replacing every through via would not necessarily help, because some signals genuinely need the full transition and some regions already have adequate space.

Check the build sequence

Altium's buried-via discussion emphasizes the relationship between via spans and fabrication stages. Sketch intermediate assemblies to determine when each connection is created. Do not assume any chosen start/end pair is feasible just because the CAD tool can represent it.

  • Confirm which spans are supported in the selected stack.
  • Review interactions between multiple restricted via spans.
  • Keep drill outputs separated and named by the relevant pair.
  • Identify the intermediate features that later become inaccessible.

Audit the finished layout by type

Filter vias by their defined structure and inspect unexpected uses. A copied footprint or reused routing fragment can introduce a span that belongs to an older stack. Compare the used via types with the released cross-section, and remove obsolete definitions that might be selected during a late edit.

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

Is every blind via a laser microvia?

No. Blind describes where the via connects in the finished board. The fabrication method must be specified separately.

Can a buried via improve signal behavior automatically?

No. It changes geometry and available routing space. Evaluate the actual signal and return path, including all remaining transitions.

References & further reading

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