Rigid-flex HDI combines dense interconnections with a board that contains both rigid and flexible regions. The design must satisfy electrical routing and mechanical movement together. A structure that works inside a rigid section cannot automatically be extended into a bend region without reviewing the flex construction and use conditions.
Define where the board moves
Identify static bends, installation folds and any repeated motion. Show bend regions, rigid-to-flex transitions and mechanical keepouts in the drawing. The required behavior depends on the complete construction and loading, so obtain a reviewed bend recommendation for the actual stackup rather than applying a generic radius everywhere.
Keep components, stiffeners, connectors and enclosure constraints visible in the same review. Their placement can change how stress reaches the flex region even when the nominal bend line is unchanged.
Coordinate the mechanical and electrical package
| Drawing information | Decision it supports |
|---|---|
| Region-specific stackups | Shows which copper and dielectric layers exist in each area |
| Bend and transition zones | Defines where routing and interconnect restrictions apply |
| Stiffeners and mounting features | Explains the mechanical support and load path |
| Via arrangements | Identifies structures requiring specific fabricator approval |
Review the transition, not only the flat artwork
Trace paths, copper distribution and layer transitions need to be evaluated in the assembled shape. A flat view may hide interference with a housing or a locally constrained bend. Use mechanical models and an agreed assembly sequence to review those conditions.
For an illustrative compact instrument, compare a single rigid-flex structure with connected rigid boards. Record connector reliability needs, assembly access, enclosure space and repair strategy alongside routing density. Rigid-flex is a system-level choice, not a guaranteed reduction in total cost.
Release and validate the use condition
Specify whether the flex is bent once during assembly or moves during service. Define the relevant verification and acceptance criteria with the product owner. Keep the tested construction, bend geometry and loading conditions associated with the results.
If a later change alters materials, reinforcement, transition geometry or the mechanical restraint, review whether the earlier evidence remains applicable. Do not let an electrical revision obscure a mechanical change. This site does not claim a particular rigid-flex layer count or dynamic-flex capability without verified client information. Use the rigid-flex drawing guide to prepare the RFQ and the HDI manufacturing guide to align the interconnect requirements.
Continue the engineering review
- HDI PCB materials selection
- HDI PCB design guidelines
- HDI PCB prototype validation
- HDI PCB engineering hub
Review your HDI requirements
Share the board revision, proposed stackup, quantity and open questions. Include the requirements discussed in this guide so the project review starts with the same assumptions.