Describe the duty before choosing the foil
Record whether the circuit is formed during installation, occasionally serviced, or repeatedly moved. For movement, define the path, local construction, environment, and acceptance plan. Ask for foil data relevant to those conditions rather than ranking every RA and ED product in one universal order. The motion classification guide helps separate different requirements.
Copper-grade request for a flex design
| Decision | Define | Review |
|---|---|---|
| Motion | Path, cycles and local bend construction | Relevant grade-specific evidence |
| Copper build | Base foil and later plating | Finished thickness by region |
| Direction | Supplier guidance and bend orientation | Panel and artwork constraints |
| High-frequency use | Surface treatment and model assumptions | Channel validation |
Keep foil and plated copper distinct
The selected laminate foil is only one contributor to finished copper. Where plating is added, confirm its location and the finished construction used for the mechanical review. Also identify surface treatment and any directional requirements for the chosen foil. Use the foil-direction guide to communicate a requirement that must survive panel planning and fabrication.
Review electrical tradeoffs independently
Mitsui Kinzoku offers electrodeposited foils with different surface-treatment purposes. That illustrates why an ED label is too broad for a high-frequency selection. Request the actual foil and roughness information used in the signal model, while assessing mechanical suitability through a representative build. If a foil alternative changes either interface loss or movement behavior, document both review paths before approving it.
Before you release the design
- Name the foil grade where qualification requires it.
- State the expected finished copper construction.
- Record direction requirements on the drawing.
- Define how a substitute foil will be reviewed.
Watch points
- Neither a foil label nor a coupon endurance number guarantees assembly bend life.
Practical questions
Should every dynamic circuit use RA?
Do not turn a common selection preference into a universal rule. Review the specific foil, processing, geometry, and product test evidence.
Does ED identify one surface roughness?
No. Ask for the relevant product data and surface treatment; broad production terminology does not define the channel model.
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.