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» PCB & ASSEMBLYThe future of electronics design: embracing flexibility and versatilityTop 10 design rules for flexand rigid-flex PCBsAs electronics become smaller, lighter, and more complex, flexible printed circuits(FPCs) and rigid-flexible printed circuit boards (RFPCBs) have become thepreferred choice for leading product designers. From aerospace and medicaldevices to wearables, industrial sensors and new energy applications, thesetechnologies offer versatility where traditional rigid boards fall short.» Markus Voeltz, Business Development Director Europe, CEE PCBHowever, designing flex and rigid-flex PCBsrequires more than just copying rigid boardtechniques. It demands a deep understanding ofmechanical stresses, material properties, and manufacturability.To help you succeed, here are CEE PCB’sTop 10 design rules for flex and rigid-flex PCB success.2. Avoid right angles in bend areasAcute angles create stress concentration points. Inflex zones, use curved traces or bends at obtuseangles to prevent cracking or delamination. Smoothrouting ensures better mechanical durability, especiallyover repeated bends.1. Define flex and rigid areas earlyStart by clearly distinguishing which areas of theboard will be flexible and which will be rigid. Thiswill affect material selection, stack-up design, bendreliability, and component placement. Early planningreduces the need for costly redesigns later. Rigidareas can be just mechanical stiffeners or traditionalFR4 material that include areas with standard PTHs(Plated Thru Holes).Acute angles create stress concentration points, here not good...Source: CEE PCBEarly planning reduces the need for costly redesigns laterSource: CEE PCB... here goodSource: CEE PCB28 EPP Europe » 05 | 2025
3. Keep vias out of flex zonesPlacing vias in bend regions weakens the structureand increases failure risk. Vias should only be used inrigid areas or stiffened zones unless specifically designedfor dynamic flexing (which requires advancedmaterials and testing).... goodSource: CEE PCBNot good: vias design in the bending areaSource: CEE PCB5. Stagger traces across layersIn multilayer designs, don’t stack traces vertically inthe flex zone. Instead, stagger them between layersto reduce the risk of stress fractures and improveflexibility. This design technique also reduces impedancemismatches in signal lines.Source: CEE PCBOK: Via distance to edge of bend area ≥1mm4. Use tear drops and anchor stubsWhen transitioning traces to pads that containplated vias, teardrop shapes help reduce stress andimprove mechanical reliability. Anchor stubs on padsin flex regions can prevent pad lifting under flexstress.NG, multilayer design with stacked wiring not staggeredSource: CEE PCBWhen transitioning traces to pads that contain plated vias,teardrop shapes help reduce stress and improve mechanicalreliability, not good...Source: CEE PCBOK, Multilayer design with staggered stacking and routingSource: CEE PCBEPP Europe » 05 | 2025 29
