Trace forces into the product
Identify insertion, withdrawal, cable pull, assembly manipulation, vibration, and operating movement that can load the circuit. Draw where each force is reacted. Use connector planning to include terminal handling. If the load path ends at a solder joint or unsupported pad, review a way to transfer that load into an intentional support.
Load-path review
| Requirement | Question to resolve | Drawing or process record |
|---|---|---|
| Connector handling | Where do mating and withdrawal forces go? | Terminal support and access drawing |
| Attached lead | What prevents pull from reaching the joint? | Retention and joining arrangement |
| Moving span | Which region is intended to deform? | Motion and support boundary map |
| Clamp or adhesive | Can the restraint shift or damage the flex? | Representative assembly and load test |
Coordinate the support boundary
Inspect the end of every stiffener, clamp, adhesive attachment, and rigid component region. Review its position relative to the expected curve and conductor transitions. The stiffener placement guide helps identify these boundaries. Do not treat a stronger local attachment as automatically better; it can move deformation to a different, less prepared location.
Test the actual handling and motion
Define load directions and handling events that represent the product. Include the real fixture edges, retention features, and installed free length. Observe where the circuit deforms and inspect terminals and support transitions after exposure. If a restraint slips or the free span changes, record it as part of the result rather than assuming the original geometry remained valid.
Before you release the design
- Identify the force direction for each handled interface.
- Show the exact ends of supports and bonded attachments.
- Check the installed free length after enclosure closure.
- Inspect both the restraint and the adjacent flexible region.
Watch points
- Adding a stiffener can relocate a stress concentration rather than eliminate it.
Practical questions
Is strain relief only needed for dynamic flex?
No. Assembly, connector service, or a pulled lead can load a static circuit. Define the likely handling and operating forces for each terminal.
Can an adhesive patch serve as strain relief?
It may be part of the design if its material, bond, geometry, load, and environment are reviewed. Verify the complete attachment and the new transition it creates.
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.