Electrical – How to connect a flat flex cable to pins of Arduino/RPi

I designed a product line that used the FFC's and what I found is that long cables (about 12 inches) would tend to work loose in shipping. Basically, there was enough cable flopping in the breeze, with enough mass, that when the box was bumped around there was enough force/torque that it cable could come out of the connector. Fastening the cable down along it's length, so it couldn't flop around so much, helped a lot.

In the same product, we have a small LCD with a short (1 inch) FFC on it. We have never had an issue with this one.

This product line has since been redesigned to eliminate the FFC's (except for the LCD). The FFC's were an expensive mistake for us.

What you're talking about is a flex(ible) circuit. They are often made by different factories from rigid board, perhaps with the same corporate name.

They are available with various numbers of layers, thicknesses of copper, features such as stiffeners and finishes and other options. Often they use orange polyimide (Kapton is one trade name) for the polymer substrate.

Shopping recommendations are off-topic, but you can find many sources for flex circuits. You use more-or-less the same CAE tools to design them, but NRE costs tend to be higher. Prototyping thus tends to be expensive.