Flexible and rigid-flex PCBs require specific design considerations to ensure reliability and manufacturability. Adhering to these fundamental rules is crucial for successful projects.
Determine the type of bend: static or dynamic. This dictates the minimum bend radius to prevent conductor damage.
For dynamic flexing, use a larger bend radius (e.g., 10x the flex layer thickness). For static bends, a smaller radius may be acceptable.
Solid copper planes can crack during bending. Use hatched or cross-hatched polygons to improve flexibility.
Route traces at a 90-degree angle to the bend line to minimize stress on the conductors.
Place vias and component pads outside of flexing regions to prevent cracking and connection failure.
Incorporate rounded corners in the flex outline instead of sharp 90-degree angles to reduce tear points.
Add stiffeners or use a gradual, tapered transition to manage stress where the rigid and flex sections meet.
Flex materials can expand and contract. Allow for slack in traces and avoid placing rigid components on flex areas.
Work with your manufacturer to define the correct arrangement of adhesive, coverlay, and copper layers for your application.
Engage your PCB fabricator during the design phase to validate your stack-up, tolerances, and material choices.
Following these design rules will enhance the durability and performance of your flexible and rigid-flex printed circuit boards.
