Separate manufacturing clearance from electrical clearance
A supplier’s minimum gap describes what it can fabricate. The voltage and environment may require a much larger distance. Use the stricter requirement and account for tolerances, conductor edge shape and contamination.
Specify where dimensions are measured
An etched conductor can have different top and base widths. Plated structures also have process variation. Define the measurement convention and critical dimensions on the finished part. Avoid using a nominal CAD width as if it were a guaranteed minimum conducting cross-section.
Use coupons for critical features
For narrow gaps or sensitive RF geometry, agree on representative process-control structures and measurement methods. Inspect multiple locations and lots where the application requires it. Do not extrapolate a supplier’s best demonstration feature to an entire production panel without evidence.
Engineering example
A 50 µm feature advertised for a fine-film process cannot be transferred to a thick-copper DBC layout. Select the route before committing to the routing density.
Before you release the design
- Obtain rules at the required copper thickness.
- Distinguish electrical insulation from fabrication spacing.
- Call out critical finished dimensions.
Sources and further technical reading
Manufacturer references support the material and process context. Worked examples and checklists are engineering guidance; they are not test results or supplier guarantees.