The interconnect cable is the cable that connects the logic board to the lower end spring connectors, EMI grounding connectors, and antennas. You could confidently [product|IF408-015|purchase one from iFixit] and not have to worry about any damage to it as they provide a lifetime warranty. Your phone should have one already however if it isn’t working or is damaged(ripped), you will run into issues with things like Wifi, Cellular, and BlueTooth.