How to Extend the Lifespan of Flexible PCB Boards

Extend the Lifespan of Flexible PCB Boards

The lifespan of flexible PCB boards is affected by many factors, including the materials used, manufacturing techniques, storage conditions and environmental factors. By taking these factors into consideration, designers can extend the lifespan of their PCBs and ensure long-term reliability.

A flexible pcb board is designed with copper traces that represent electrical conductors. These traces may be coated with polyimide or left bare. The traces that are covered by polyimide have been shown to offer better fatigue performance than those that are bare. A recent study conducted on flex circuits showed that bare copper traces fail after thousands of cycles, while those covered by polyimide endure hundreds of thousands of cycle before a failure.

During the test, the traces were subjected to extreme twisting, mimicking conditions that might be encountered in dynamic applications. The results of this testing found that traces that were uncoated and had a tighter bend radius were more likely to fail than those with larger or broader bend radiuses. In contrast, there was no evidence of failure for traces that were coated and had a wider bend radius.

How to Extend the Lifespan of Flexible PCB Boards

The study also included optical inspections of the traces using an Aven Tools digital microscope, which provided magnified images of all signal traces on the flex circuits to look for cracking or other damage. Optical inspections also revealed that all trace failures occurred at the trace-to-pad interface. Furthermore, no evidence of cracking or damage to the polyimide was observed.

When designing a flexible circuit, it’s important to keep in mind that it should be a dynamic design rather than a static one. This will help reduce stress in the bend area and extend its life. Staggering signals on a flexible circuit can also prevent stress from building up in a specific location over time.

In addition, avoiding tight bends will prevent stress and damage to the circuit. Sierra Circuits recommends that the bend radius for your flex circuit should be at least 10 times the width of the conductors, and that you keep vias away from the flex circuit’s bend area. If you can, avoid using end cutouts / slits in flex circuits, as they can be more prone to peeling from the flex layers than regular holes.

In addition to choosing quality materials, ensuring proper manufacturing techniques and storage conditions can significantly enhance the lifespan of your flexible PCB. By storing your circuits in a controlled environment, keeping them away from moisture and ensuring they are not exposed to temperature or humidity changes, you can minimize the degradation of their materials and components and increase their longevity.

By following these simple tips, you can extend the lifespan of your flex PCB and improve its reliability. To learn more about how to achieve the best results with your flex circuit, watch our webinar, Flex PCB Design Guidelines for Manufacturing. We’ll discuss the key aspects of successful flex circuits and show you how to get the most out of your production runs.