Multilayer PCB vs Flexible PCB

[Jasonkeel]

Does anyone know in what specific application you would use a multi-layer PCB vs. a flexible PCB? Any example would be very helpful.

[PeteKnight]

@Jasonkeel obviously one is rigid and the other is flexible!
Flexible PCBs are found in things like RGB LED strips, where components need to be mounted to a flexible substrate, whereas rigid single/multi layer PCBs are used for the majority of PCB designs because you want the substrate material to be rigid and easy to mount in enclosures.
Mounting discreet non-flexible components onto a flexible substrate has its issues, as the pads that connect to the components can tear if the pcb is bent through too tight a radius.

Pete.

[bjacobse]

Inside Hearing aids, the PCB are "mainly" only flexible PCB as the PCB must bend and follow the mechanical shape, think this picture gives an idea
https://www.manualslib.com/manual/1902167/Oticon-Aurora-Minirite-312-T-Rc.html

[Jasonkeel]

Thank you @PeteKnight for giving me such a easy to understand explanation.

[Jasonkeel]

Thanks @bjacobse. I tried even before to understand from pictures but I'm still a learner so can not understand much.

[bjacobse]

@Jasonkeel
The green is the flex PCB,, as you can se how it' turn 90degree a few times