A rigid-flex fabrication drawing must describe the board as both an electrical interconnect and a mechanical assembly. The rigid regions, flex regions, transition boundaries and intended bend condition need a common coordinate system. A layer count alone does not communicate how the product will be fabricated, assembled or installed.
Describe the physical configuration
Provide a flat-pattern view and a clear representation of the installed configuration. Identify rigid outlines, flex lengths, cutouts, stiffeners and interfaces to the enclosure. Distinguish a bend made during installation from repeated flexing in service. Share the expected movement and environmental conditions so the construction can be evaluated against the application.
A mechanical model is useful for reviewing fit, but the controlled drawing still needs to define the dimensions and tolerances that will be inspected. Identify the datum scheme and the features that locate the assembly. Clarify whether a measurement applies before bending, after installation or in another specified condition.
Document the construction by region
| Drawing feature | What to clarify |
|---|---|
| Regional stackup | Which materials and copper layers exist in each rigid and flexible region. |
| Coverlay and mask | Coverage, openings and boundaries relative to pads and transition areas. |
| Vias and holes | Layer spans, finished requirements and permitted locations. |
| Mechanical reinforcement | Stiffener geometry, attachment and interfaces to connectors or fixtures. |
| Assembly support | Panel, carrier or fixture requirements for handling and processing. |
Review bend areas and transitions together
Ask the fabricator to review the proposed copper routing and local construction around each bend and rigid-to-flex transition. Obtain project-specific recommendations for geometry and fabrication tolerances. Do not apply a single bend-radius number to every construction without considering thickness, copper arrangement, materials and the intended number of flex cycles.
As a review example, a connector may fit within the nominal enclosure model while its stiffener extends into the planned bend area. Resolving that interference before layout release avoids treating it as an assembly adjustment after boards have been built. Keep the electrical and mechanical revisions synchronized when the interface changes.
Include verification in the purchase package
- Identify critical flat and formed dimensions and how they are measured.
- State the required electrical test and traceability information.
- Define any application-specific flex or environmental evaluation.
- Agree acceptable handling, packaging and assembly fixtures.
- Record which deviations require engineering approval.
Approved rigid-flex constructions, manufacturing tolerances and qualification evidence are [NEEDS CLIENT INPUT]. If the design also uses microvias, review the HDI planning guide alongside the rigid-flex drawing. Discuss the proposed construction