What is the bend radius in flexible PCBs?
bend radius in flexible PCBs
A flex circuit board can bend, twist, and loop to accommodate the required functionality of a product, but there are limits on how much stress a flexible PCB can withstand without damage or shortening its lifespan. The bending radius is a measure of how far a PCB can be bent before it will break, and it depends on a number of factors. The thickness of the PCB and the number of layers affect its bending capability, but also trace layout, component placement, and the manufacturing process influence a PCB’s flexibility.
The bending radius is the minimum distance that can be stretched between the edges of a bare copper layer in a flexible printed circuit board (FPC). It’s important to take into account the bending radius when designing an electronic product so that the FPC will be able to bend, twist, and loop as needed for its intended application.
When a flexible PCB is bent, it experiences both compressive and tensile forces, which must be balanced to maintain a high level of reliability and durability. The tensile force on the inner side of the bend exerts pressure against the traces, while the compressive force on the outside of the bend exerts a shear stress against the coverlay and copper plane.
What is the bend radius in flexible PCBs?
Considering the varying stress that a flex PCB will experience when it’s bent, it’s important to calculate the bending radius early in the design phase. This will allow designers to ensure that the flex circuit can tolerate any number of bends during its lifecycle without damaging the copper or shortening its lifespan.
In general, the higher the number of layers in a flexible pcb, the larger the bending radius should be. For a one-layer design, the bending radius should be at least 6X the thickness of the final PCB, while a multi-layer design should have a bending radius of at least 15X the finished PCB thickness.
A larger bending radius can also help to reduce the risk of trace fractures, which are a common cause of failure in flexible circuit boards. The root causes of fractures are complex, but they can be caused by a combination of factors including material thickness, trace alignment, component placement, and manufacturing processes.
Choosing the correct bending radius for your design can save time, money, and headaches when it comes to manufacturing. PCBway has a detailed calculator that can help you find the right bending radius for your flex circuit. Additionally, a large bend radius can increase the life of your flex PCB by reducing stress levels on the copper and other components in the area. For best results, avoid using sharp angles in the expected bending region and instead use rounded corners that are more resilient to damage. This will also reduce the need for costly stiffeners, which are rigid sections of PCB that are laminated to a flex circuit to provide additional structural support.