Translate the system need into a board requirement
Record single-ended or differential targets, tolerances, relevant interface requirements, and the controlled net names. Separate these from a suggested trace width. Use pair planning where applicable. Agree whether the review covers only the bare flex’s impedance or also the assembled channel through connectors and rigid-board launches.
Impedance requirement record
| Review item | Design question | Evidence or action |
|---|---|---|
| Electrical target | Which type, value and tolerance apply? | List controlled nets and system source |
| Construction | Which regional stack does the route use? | Provide agreed layer and material definitions |
| Geometry | What may manufacturing adjust? | Require approval of proposed changes |
| Acceptance | What is measured and how is it reported? | Agree coupon and product relationship |
Model the construction that will be made
Give the fabricator the proposed copper, finished dielectric arrangement, coverlay, references, and regional transitions. The stackup workflow keeps these inputs together. Material data must retain frequency and test context. Allow proposed geometry changes to return for approval rather than silently treating a preliminary CAD value as a production limit.
Define acceptance and change control
Discuss the measurement method, coupon relationship to the product, reporting, and disposition of exceptions before release. Identify whether the coupon represents the same layers and process as the controlled route. If material, copper, coverlay, or reference geometry changes, reopen the relevant analysis. Store approved dimensions and test expectations in the released drawing package.
Before you release the design
- Name controlled nets rather than labeling the entire board high speed.
- Keep material-property conditions with modeling inputs.
- Include connector and reference transitions in channel review.
- Agree the validation deliverables before quotation.
Watch points
- A nominal dielectric constant does not determine finished impedance by itself.
- A coupon result does not automatically demonstrate complete interface compliance.
Practical questions
Can the fabricator choose the trace width?
You can authorize a reviewed geometry proposal against your target and construction. State which dimensions may change and require approval where the change affects routing or mechanical intent.
Does every signal need impedance control?
The system's electrical requirements decide. Identify critical nets and use appropriate analysis; blanket requirements can add work without defining a meaningful acceptance condition.
Technical references
References support the material or design context. Check the exact grade, part number, document revision and project conditions before release.Updated 27 September 2026 · Technical content policy · Engineering guidance supports project review; the agreed drawing defines the build.