Trace the electrical path
Draw which copper layers connect through each region. A passive stiffener beneath existing flex copper does not create additional routed layers. A rigid-flex proposal should identify the rigid and flexible substacks and their interconnection. The rigid-flex region guide explains how to communicate this architecture without relying on a perspective rendering alone.
Architecture choice by requirement
| Feature | Define | Review |
|---|---|---|
| Mechanical support only | Existing flex routing is sufficient | Stiffened-flex concept |
| Extra rigid routing | Copper layers needed in a rigid island | Rigid-flex substack proposal |
| Service strategy | Replaceable versus integrated assembly | Connector and repair tradeoffs |
| Qualification | Installed motion and environment | Representative architecture samples |
Compare the assembly problem
List components, connector mating loads, fastening, handling, and enclosure constraints. A supported flex island may be enough if routing already fits the flex. If routing density or component interfaces need a different rigid section, evaluate that construction explicitly. Use the FR-4 stiffener guide for the support-only option and compare the same electrical functionality on both sides.
Review changes in release and testing
Ask for a region stack and fabrication approach for each viable architecture. Compare total assembly steps and verification needs rather than only bare-board prices. Altium’s documentation describes region-specific substacks, which is useful for communicating a rigid-flex concept. Preserve the difference between geometric modeling and qualification: neither an attractive fold view nor a layer-count label demonstrates the installed assembly’s reliability.
Before you release the design
- Map copper continuity across regions.
- Separate routing needs from support needs.
- Compare equal assembly scope.
- Obtain a proposed construction for each serious option.
Watch points
- Calling a supported flex region 'rigid-flex' can leave the fabricator uncertain about the intended electrical construction.
Practical questions
Can stiffened flex carry mounted components?
It can be proposed with a reviewed support and assembly process. Define loads, attachment, and inspection around the actual components.
Is rigid-flex always more reliable?
Reliability depends on the product and construction. Evaluate connectors, transitions, manufacturing complexity, and the relevant qualification evidence.
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.