Flex soldering is more difficult to master than rigid soldering. The core principles for soldering components stay the same, but flexibility implies coping with diverse material handling and adaptability.
However difficult, we must learn to deal with them because they're here to stay.
The smaller the electronics get and trends like foldable phones continue to rise; the need for small flexible PCBs is real.
If you're soldering them by hand, you have to know which temperature is the right one.
If you're designing the PCB, you have to know where to place the components, so they don't bend and break.
If you're in charge of mass manufacturing or the project manager, you must know the difference between the SMT process for rigid PCBs and flexible PCBs.
In short, there's much to learn about working with flexible PCBs.
Here's an article that breaks down in 7 steps what you have to pay attention to.
https://titoma.com/blog/flex-soldering
