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Having never worked with flexible PCB's before I was wondering how much and how often it can be bend? I'm thinking of using a flex PCB inside a pet collar where it would have to fold in order to adjust collar length.

Would a flex PCB be able to cope with this much mechanical stress?

Thanks for sharing your thoughts!

Jason Schot
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    This would be in the specs of a proper board house. The band of a collar has much more chance of working than something that needs to go through a buckle, almost *any* material takes damage there. You also need to think about the solder joins of parts like ICs and large capacitors which don't bend - and for the capacitors, *internal* stress too. – Chris Stratton Mar 10 '19 at 17:40
  • Depends on the manufacturer. One example: minimum static bend radius (radius!) 10x the PCB thickness for single and double layers, 20x for 4 layers. Dynamic bend radius 100x for 1L, 150x for 2L, not recommended for 4L. Semi-dynamic bend: 20x for 1L/2L, 50x for 4L. In case of the dog collar, I'd say it's probably semi-dynamic, single layer, thickness 90µm, so 1.8 minimum radius, 3.6 minimum diameter. Your manufacturer might give you different numbers. – Klaws Feb 05 '21 at 08:46

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As with most engineering questions, the answer is "it depends".

You can purchase flex circuits optimized for frequent bending (dynamic) applications, and you should minimize the copper thickness, and ideally use just a single layer, to make the PCB as robust as possible. Tight radius bending is bad, but how bad depends on the flex construction (number of layers, substrate), and thickness and type of copper you specify from the maker. If you need multiple layers, consider using more than one single or two layer flex.

Repeated bending with a tight radius (a small multiple of the substrate thickess) should be avoided.

Spehro Pefhany
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  • Thanks for the fast response. The idea would be to use the flex PCB for power transfer only. Would you recommend thin insulated wires over a flex PCB for this purpose? – Jason Schot Mar 10 '19 at 17:45
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    You would probably have less trouble with the wires if they do the job. I had an LED dog collar that (I think) used wires and it lasted pretty well, almost outlasted the dog herself. You could buy some and tear them apart for research purposes. – Spehro Pefhany Mar 10 '19 at 17:48