Rigid Flex PCBs Design Best Practices for Reliability

As modern electronics continue to get smaller, lighter, and more durable, rigid flex PCB design best practices have become more important than ever. These boards combine the strengths of both rigid and flexible PCBs, creating reliable and space-saving designs. But to get the best performance, you need to follow clear design rules that balance both electrical and mechanical needs.

Why Rigid Flex PCBs Design Matters

Rigid flex PCBs are more than just a space-saving solution. When designed well, they provide: 

• Fewer connectors, which means fewer possible failure points

• Better signal quality, thanks to shorter wiring paths

• Greater strength in environments with vibration or movement

• Easier assembly, with less wiring and manual labor

However, these benefits only come when the design is done correctly. Every choice—from how you route traces to what materials you use—affects how well the board will work.

Layer Stack-Up Tips

The stack-up is the foundation of any rigid flex PCB design. Some simple tips: 

• Keep layers balanced to avoid bending during soldering

• Use dedicated ground layers for signal control

• Reduce the number of layers in the flex part so it can bend properly

• Use glue-free flex materials in tight-bend areas

A good starting point is a 6-layer board, with 2–4 rigid layers and 2 flexible ones in the middle. The IPC-2223 standard gives helpful stack-up recommendations.

Flex Region Design Tips

The flexible portion of a rigid flex PCB is prone to fatigue if improperly designed. Here’s how to improve durability: 

• Use arched trace routing instead of sharp angles 

• Don’t place vias in the bend area 

• Maintain a minimum bend radius of 10x the flex thickness 

• Add coverlays and stiffeners to reduce mechanical strain 

Also, try to place traces on the neutral axis of the bend to minimize tensile/compressive forces.

Material Selection

Materials impact everything from signal performance to temperature resistance. Good options include:

• Polyimide films for flex areas—they resist heat and chemicals

• High-Tg FR4 for rigid areas to stop layers from separating

• Low-Dk materials if signal speed is important

• Adhesive-free designs for tight bends and better reliability

Always choose materials that meet IPC-6013 standards for high-reliability products.

DFM and Assembly Considerations

Design for Manufacturability (DFM) plays a huge role in keeping production costs down and yields high. To avoid surprises: 

• Involve your flex PCB fabricator early in the design stage 

• Avoid overlapping stiffeners and coverlays 

• Provide clear documentation for bend zones and bend directions 

Also, test your design with simulations or physical samples before full production. Flex Plus offers support in both layout and prototyping to help you catch issues early.

Final Thoughts

When done right, a rigid-flex PCB can work better and last longer than traditional PCBs, especially in tough environments. Following these simple best practices will help you create a design that’s easy to build, cost-effective, and—most importantly—reliable.

If you're starting a new project and need help with layout or manufacturing, don’t hesitate to reach out to a rigid flex expert like Flex Plus. Getting advice early can save time and avoid mistakes later on.