Rigid vs flex cable board to board connection

Question

I am working on a project, that has 2 separate PCBs in one enclosure, those PCBs should talk on 20 pins (GPIO). The entire system is prone to low to moderate vibrations. While there is no concern around PCBs themselves, I am rather concerned about the connection between them. I so far see 3 choices:

1. Rigid connection via IDC connectors 1.27mm pitch THT. This seems to be fairly cheap option, but considering vibrations, will require some additional mount points between PCBs to avoid disconnect due to slippage and also it will probably cause some strain on the connector solder joints.
2. Ribbon cable using IDC connectors. That seems to be middle ground on price, avoids strain on connector solder joints, but it is bulky and still would probably be prone to slippage?
3. FFC cable - seems to be most compact non-rigid solution, but rather expensive and I have no idea whether it is reliable in environment with vibrations.

I am so far inclined more towards option 2. But I don't know whether this is a good choice and whether I am missing some aspect that would result in unexpected failures.

I guess my questions are -- is the analysis of each option above correct? Is there any other option I overlooked?

Answer 1

Wire-to-board is cheaper than both FFC and IDC, as it uses ordinary bulk wire as its main material. It’s widely used in consumer electronics. Done correctly, the crimp terminals are very robust to vibration. Wire-to-board also gives wide flexibility in cable type - it’s possible to mix coax and single wires for example, as is done for USB and HDMI cables.

FFC is used when space is at a premium or the pin count is high, or there’s a signal integrity concern. It’s ok for high-vibe when the right retention is used. It sees use for moving assemblies for example (think printers and suchlike.)

IDC isn’t nearly as popular as either wire-to-board or FFC, being both bulky and expensive (needs ribbon cable.) It’s also not a good choice for high-vibe environments due to the difficulty of maintaining a gas-tight contact with repeated flex stress.