Identify every drilling group

Create a list of through holes, buried spans, blind microvia spans and nonplated features. Give each group a name that maps to the approved stackup. If two groups use the same nominal diameter but connect different layers, their roles must still be distinguishable.

KiCad documents Excellon and Gerber X2 drilling outputs and options for units, coordinate origin and zero formatting. Whatever CAD tool is used, record the relevant export settings instead of assuming the receiving system will infer them correctly.

Treat dimensions as agreed definitions

State whether a specified hole value is a finished requirement or a process value. Let the fabricator propose appropriate production tooling within the agreed requirements. For microvias, confirm how diameter and depth are defined in the construction discussion, because a tapered feature is not described fully by one unlabeled number.

Describe slots, routed features and plated edges explicitly. A shape shown only on a mechanical drawing can be missed by an automated import. Reconcile it with the digital data and ask how the receiving workflow represents that feature.

Run a visual alignment check

Load all exported copper layers, drill groups and the true board profile into a viewer using the intended units and origins. Check several known pad centers and mechanical holes. Inspect both sides and buried spans; a top layer screenshot alone cannot reveal a wrong internal connection.

  • Verify each file's units, precision and coordinate origin.
  • Compare drill counts with the CAD report by span.
  • Separate plated and nonplated intent unambiguously.
  • Confirm slots and cutouts appear in the receiving data set.

Release maps as interpretation aids

A drill map helps people review the file set, but should not become a competing source of coordinates. Label maps with the same board revision and retain the export manifest. If a supplier modifies a drilling interpretation, capture the proposed change and obtain a documented engineering disposition.

On a later revision, regenerate the complete drilling set. Replacing only one file in an old archive can leave obsolete holes or spans active and creates an avoidable ambiguity about which combination represents the design.

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

Can all HDI holes be placed in one undifferentiated file?

Only if the agreed format and workflow preserve every required span and attribute unambiguously. Otherwise separate groups and a clear map are needed.

Is a drill map sufficient manufacturing data?

It is primarily a review aid. Supply the agreed digital drill or intelligent design data and verify that the map represents the same released revision.

References & further reading

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