How to Ensure Bend Radius Compliance in Flexible PCB Designs
Bend Radius Compliance in Flexible PCB Designs
Flex PCBs are often used for industrial and consumer applications that require them to bend. However, it’s important to consider the mechanical stresses on the copper circuitry in your flex PCB design. Without proper design consideration, you could create a flexible board that exceeds its bending capabilities. This could lead to failed components and long term reliability concerns. To help prevent this, you’ll need to consider the following flex PCB design tips.
Ensuring that conductive traces are routed in a manner that conforms to the specified bend radius will help prevent stress concentration on these traces during bending and flexing operations. This will help to maintain signal integrity and electrical performance in the flex area of your PCB. Choosing substrate materials that offer optimal mechanical flexibility can help to ensure that your flex PCB can bend and flex with minimal damage to the copper. This includes the use of flexible polyimide-based substrates.
The use of staggered conductive layers in multi-layered flexible pcb board designs can help to improve the flexibility of your traces. This is done by placing a layer of copper on each side of the neutral bend axis. This helps to balance the weights and thicknesses of each flex zone.
How to Ensure Bend Radius Compliance in Flexible PCB Designs
If your flex PCB is designed for dynamic bending, it’s essential to avoid placing pads, holes, and vias in the flex region of the circuit board. These areas are subject to compressive and tensile stresses that can apply mechanical stress on the copper circuitry, which can cause it to fail or tear. This is particularly true if you’re using a rigid-flex board, which is a rigid section of the PCB that’s attached to a flexible section with stiffeners.
Performing detailed flexibility analysis can help to ensure that your flex or rigid-flex PCB design will meet the minimum flex bend radius requirements. Flexibility analysis can also provide you with valuable data to determine if the board can bend to the desired angle without structural damage.
If you’re designing a new flexible PCB, it’s important to ask your CM for a stack-up. This will help to ensure that your PCB can flex properly and that it’s designed with the correct materials for your project. This can help you to avoid costly mistakes that will negatively impact your final product’s quality and durability. For example, you should always request a copper layer that’s at least 10 times thinner than the base material.
This will ensure that your traces are thick enough to withstand the bending forces that they will be subjected to during fabrication. You should also make sure that your traces are routed perpendicular to the overall bend. This will reduce the stress that is placed on the traces during overforming and will increase their durability. It’s also important to ensure that all plated through holes are located at least 500um (0.020″) away from the flex zone of your circuit board. This will reduce the likelihood that a slit in the flex will tear.