PCB Stiffeners for Small Flexible Circuits

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1

Hey everyone,

I need to design a compact PCB for a small embedded project. I’m thinking about using a flex-rigid PCB. I want to keep it thin while allowing some flexibility. It’s somewhat similar to how thin flexible circuits are used in compact sensors, like the SpectraFlex™ Flex Sensor.

Since the flex section will have an FPC connector, I’m worried about mechanical stress and durability, especially where the flex meets the rigid part. I came across this article: PCB Stiffeners: Enhancing Durability in Flexible Circuit Designs. It explains how stiffeners can reinforce flex PCBs and prevent failures. I read it but I still have some questions. I am writing my questions one by one.

  1. Has anyone here used stiffeners for small flex circuits?

  2. Are FR4 stiffeners effective for reinforcing connector areas, or do they add unnecessary bulk?
    I’d like to hear from anyone who has worked with flexible PCB designs!

2

FR4 stiffeners can be a great choice for reinforcing flex PCBs, especially around connector areas, as they help prevent mechanical stress and improve durability. However, if space is a concern, they might add a bit of bulk. In such cases, polyimide stiffeners could be a better option since they offer support while keeping things slim. The key is ensuring a smooth transition between the rigid and flex sections to prevent stress buildup, which can lead to cracks over time. If your design involves frequent bending, reinforcing only the connector area while keeping the flex section as free as possible can help maintain both durability and flexibility.

Have you considered polyimide as an alternative?