Use these answers to prepare a clear project brief and resolve scope before a manufacturing release.
Does a trace width define impedance?
Only within a specific transmission-line structure. Dielectric spacing, material properties, copper thickness, mask and reference conductors also influence impedance. Give the manufacturer the target, layer and reference-plane relationship.
Should impedance be checked before routing?
Agree a producible stack-up before setting final widths and differential spacing. Late material or thickness changes can require rerouting. Keep the approved stack-up with the released CAD and fabrication files.
What does a coupon measurement establish?
A representative coupon helps assess the fabrication process against the specified impedance target. Its correlation depends on the structure and placement. It does not by itself validate connectors, via transitions or the complete assembled channel.
Can geometry be adjusted by the fabricator?
Treat proposed changes as engineering questions that require approval. Review their effects on spacing, coupling, length matching and available routing area. Record the accepted geometry so repeat builds use the same baseline.