Describe the load waveform
State continuous current, pulses, startup conditions, duty cycle, and the required voltage at the load. Identify shared returns and the conditions under which several loads operate together. Use power-distribution planning to include connectors and branches. A small average load can conceal a short event that determines the circuit’s voltage-drop or thermal requirement.
Current review inputs
| Design input | Question to resolve | Review output |
|---|---|---|
| Load | What continuous, pulse and startup conditions apply? | A load-case table with durations |
| Conductor | Where is the narrowest or longest path? | Annotated power and return routing |
| Environment | What limits heat transfer in the product? | Representative thermal setup |
| Acceptance | Which temperature and voltage limits matter? | Measurement locations and pass criteria |
Define the thermal surroundings
Record trace length, width, finished copper, insulation, nearby copper, support, and enclosure conditions. Identify local neckdowns and terminal contacts, not just the widest part of a power route. Review copper thickness against mechanical duty before increasing it. A folded circuit in an enclosed product may have different heat paths from an exposed flat sample.
Measure the relevant operating cases
Use analysis to identify candidate geometry, then verify representative hardware at agreed loads and conditions. Define where temperature and voltage will be measured and how the assembly reaches the test state. Include unfavorable supported operating cases in the plan. Record the actual construction and fixture so results remain traceable when the product or enclosure changes.
Before you release the design
- State load cases rather than a single unexplained ampere value.
- Include the return conductor and both terminations.
- Check voltage drop at the load under the relevant event.
- Repeat affected review when support, copper, or enclosure conditions change.
Watch points
- Do not transfer an open-air trace result to an enclosed assembly without review.
Practical questions
Can a rigid-board trace calculator be used?
It may help explore assumptions, but confirm that its construction and heat-transfer model represent the flex. Treat the output as an estimate requiring project-specific review.
Is thicker copper always the best solution?
It can change resistance, construction, routing, and mechanical behavior. Compare wider or shorter paths, different load routing, and terminal choices alongside the thickness option.
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.