A flex circuit board can be used in transmitting signals in a quantum computing system. The flex circuit board can include at least one dielectric layer and at least one superconducting layer disposed on a surface of the at least one dielectric layer. The at least one superconducting layer can include a superconducting material. The superconducting material can be superconducting at a temperature less than about 3 kelvin. The flex circuit board can have at least one metal structure electroplated onto the at least one superconducting layer.