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Design Rules and Net Classes

Design rules express the manufacturing limits and electrical routing constraints for the active board. Configure them before routing, then use the same rules for DFM/DRC and release review.

Open Design Rules Manager

With a PCB active, select View → Design Rules. Confirm the board and unit system before changing a value.

Image — Design Rules Manager

Image needed

Capture the v1.5.47 manager with global limits and at least two net classes visible. Use clearly fictional example values and show the active unit.

Set global limits

Enter values that your chosen manufacturer can reliably produce:

Rule What it controls
Minimum clearance Allowed gap between copper objects on different nets
Minimum trace width Narrowest permitted routed track
Via diameter and drill Smallest allowed plated via geometry
Minimum drill Smallest mechanical or plated drill
Annular ring Copper remaining around a drilled hole
Board-edge clearance Copper distance from the finished outline

Do not copy “typical” internet values into a production board. Use the current fabricator's published capability and apply a margin appropriate to the design.

Create net classes

Use net classes when groups need different widths, clearances, or via sizes. Common examples are low-current signals, supply rails, high-current paths, sensitive analog nets, or controlled routing groups.

  1. Add a class with a descriptive name.
  2. Set its width, clearance, and via requirements.
  3. Assign nets by explicit name or a supported automatic rule.
  4. Review the resolved class for each critical net.

A manual assignment takes precedence when both automatic and manual classification apply. Avoid overlapping patterns whose result is difficult to predict.

Verify the effect

During routing, confirm that a new track uses the expected class width. After changes, rerun DFM/DRC and review violations involving existing geometry; changing a rule does not automatically reroute old tracks.

Short video — Assign and verify a net class

Video needed

Record a 20–30 second clip showing one supply net assigned to a class, a route using its width, and the resulting DFM/DRC check.

Release checklist

  • Rules match the selected manufacturer's current capabilities.
  • Critical nets resolve to the intended class.
  • Manual overrides are intentional and documented.
  • Existing tracks and vias comply after every rule change.
  • DFM/DRC has been rerun on the saved release revision.