Flexible Printed Circuits Be Bent Repeatedly Without Damage

Flexible printed circuits are very delicate and can be easily damaged. Various factors can cause damage to a flex circuit, including improper handling and storing the PCBs. In some cases, a seemingly minor error can ruin the entire board. For example, two metal traces may not be properly insulated and could conduct electricity between them, which would cause the circuit to fail. Fortunately, there are a few things you can do to prevent such errors and ensure your flex circuits stay intact.

The most important factor is to understand the bending capabilities of your flex circuits. You should consult with your PCB Fabrication service to learn more about the bending capabilities of your boards. This will help you decide what type of material stack-up is appropriate for your flexible printed circuit. The ductility of the copper used in your flex circuits is also an important factor to consider. A higher ductility copper foil can better tolerate the stresses of repeated bending, and it will also improve the longevity of your circuits.

In addition to the underlying copper layer, the conductive paths in your flex circuits are often made from an epoxy-based polyimide substrate. To ensure that these circuits can withstand repeated bending, you should choose an appropriate polyimide for your application. Ideally, you should choose a high-temperature version of this polyimide.

Can Flexible Printed Circuits Be Bent Repeatedly Without Damage?

Another factor to consider is the bending radius of your flex circuits. The minimum bending radius depends on the number of layers in your design, and can range from as little as six times the thickness of the flex circuit for a single-layer design, to up to 35 times the flex circuit thickness for more complex multi-layer designs. For dynamic bending applications, it is also advisable to use RA (reduced area) copper in your flex circuits, which can significantly increase the fatigue life of your circuits.

Finally, the pad and trace arrangement on your flex circuits is important. For dynamic bending, it is best to route all traces along the neutral axis of your flex circuit stackup, which will distribute stress evenly over the entire circuit. You should also avoid using pad and trace geometries that concentrate stress points at the corners of the flex circuit, as this can cause the copper to crack and eventually fail. In this exploration, we delve into the intricacies of flexible printed circuits, their composition, applications, and the transformative impact they have had on the electronics industry.

It is also a good idea to use tin finishing and soft gold coverings on your flex circuits, as these finishes can resist corrosion from oxidation caused by repetitive bending. Finally, you should always carefully handle your flex circuits during assembly and shipping to minimize the chance of accidental damage. Also, make sure that your assembly technicians are educated about the limitations of flex circuits, so that they do not inadvertently mishandle your flex circuits during the assembly process.