1. Like it or not, flex and rigid-flex PCBs are here to stay, and increasingly more flexible electronics are transitioning from the research phase to the market.
2. Flex PCBs are no longer limited to powering electric motors in magnetic hard disks; they are now utilized in a wide range of devices containing folding or rotating components, often featuring dynamic flex PCBs.
3. With the flex PCB market expanding into the tens of billions, PCB designers have a strong incentive to deepen their understanding of both static and dynamic flex PCB design, as the success of your company’s next product or redesign may depend on it.
4. **Static vs. Dynamic Flex PCBs:**
Any flex PCB is akin to a rigid-flex PCB in terms of materials used, employing polyimide primarily for flexibility, though materials like polyethylene naphthalate (PEN), polytetrafluoroethylene (PTFE), and Aramid are also viable options.
5. Flex PCBs can be categorized as static or dynamic, each demanding meticulous attention to both mechanical and electrical aspects during the design process, facilitated by PCB design software featuring ECAD/MCAD collaboration capabilities.
6. When configuring the stackup and routing traces on flex PCBs, the curved section should be treated as a curved rectangular plate during mechanical analysis to determine optimal trace density and prevent cracking and failure.
7. Regardless of whether it’s a static or dynamic flex PCB, a thicker flexible stackup necessitates a larger bending radius to mitigate tensile and compressive stresses during bending, while thinner traces can be positioned within the neutral bending axis to withstand compressive stress better.
8. **Static Flex PCBs: Production Considerations:**
Static flex PCBs undergo compressive forming during assembly to achieve the desired curvature, often exceeding the intended bend radius to induce plastic deformation and prevent reverting to the original shape post-manufacturing.
9. While thicker traces may seem intuitive for withstanding stresses during forming, thinner traces are preferred as they can better withstand compressive stress, aligning with the neutral bending axis.
10. To ensure compliance with IPC 2223C standards regarding the bending ratio, proper selection of stackup and trace density is crucial, maintaining the neutral bending axis close to the PCB centerline.
11. **Dynamic Flex PCBs: Durability:**
Many design considerations for static flex PCBs are applicable to dynamic flex PCBs, with a key focus on fatigue resistance during repetitive bending.
12. Copper layers in dynamic flex PCBs must be limited, typically to a single layer coinciding with the neutral bending axis, to mitigate work hardening and potential fracture.
13. Overlapping traces in adjacent layers should be avoided to minimize stress on traces away from the neutral bending axis, enhancing the longevity of the PCB.
14. It’s essential to allow for a sufficient margin of safety and adhere to the minimum bend radius to prevent stress concentration at the board’s edges, thereby prolonging the PCB’s lifespan.
15. **Conclusion:**
As the demand for flex PCBs continues to surge, comprehensive design software such as Altium Designer becomes indispensable, streamlining stackup design, manufacturing planning, and more within a unified interface adaptable to various PCB configurations.
2. Flex PCBs are no longer limited to powering electric motors in magnetic hard disks; they are now utilized in a wide range of devices containing folding or rotating components, often featuring dynamic flex PCBs.
3. With the flex PCB market expanding into the tens of billions, PCB designers have a strong incentive to deepen their understanding of both static and dynamic flex PCB design, as the success of your company’s next product or redesign may depend on it.
4. **Static vs. Dynamic Flex PCBs:**
Any flex PCB is akin to a rigid-flex PCB in terms of materials used, employing polyimide primarily for flexibility, though materials like polyethylene naphthalate (PEN), polytetrafluoroethylene (PTFE), and Aramid are also viable options.
5. Flex PCBs can be categorized as static or dynamic, each demanding meticulous attention to both mechanical and electrical aspects during the design process, facilitated by PCB design software featuring ECAD/MCAD collaboration capabilities.
6. When configuring the stackup and routing traces on flex PCBs, the curved section should be treated as a curved rectangular plate during mechanical analysis to determine optimal trace density and prevent cracking and failure.
7. Regardless of whether it’s a static or dynamic flex PCB, a thicker flexible stackup necessitates a larger bending radius to mitigate tensile and compressive stresses during bending, while thinner traces can be positioned within the neutral bending axis to withstand compressive stress better.
8. **Static Flex PCBs: Production Considerations:**
Static flex PCBs undergo compressive forming during assembly to achieve the desired curvature, often exceeding the intended bend radius to induce plastic deformation and prevent reverting to the original shape post-manufacturing.
9. While thicker traces may seem intuitive for withstanding stresses during forming, thinner traces are preferred as they can better withstand compressive stress, aligning with the neutral bending axis.
10. To ensure compliance with IPC 2223C standards regarding the bending ratio, proper selection of stackup and trace density is crucial, maintaining the neutral bending axis close to the PCB centerline.
11. **Dynamic Flex PCBs: Durability:**
Many design considerations for static flex PCBs are applicable to dynamic flex PCBs, with a key focus on fatigue resistance during repetitive bending.
12. Copper layers in dynamic flex PCBs must be limited, typically to a single layer coinciding with the neutral bending axis, to mitigate work hardening and potential fracture.
13. Overlapping traces in adjacent layers should be avoided to minimize stress on traces away from the neutral bending axis, enhancing the longevity of the PCB.
14. It’s essential to allow for a sufficient margin of safety and adhere to the minimum bend radius to prevent stress concentration at the board’s edges, thereby prolonging the PCB’s lifespan.
15. **Conclusion:**
As the demand for flex PCBs continues to surge, comprehensive design software such as Altium Designer becomes indispensable, streamlining stackup design, manufacturing planning, and more within a unified interface adaptable to various PCB configurations.
