The silicon sensors of the Silicon Tracking System of the Compressed Baryonic Matter experiment at FAIR, GSI are connected to the read-out electronics by low mass flexible microcables due to tight material budget restrictions. The cable length of up to 50 cm and its flexible nature make detector module assembly one of the most critical parts in STS. A novel low mass, low capacitance multilayer copper microcable has been designed and produced to facilitate detector assembly. Furthermore, a novel detector production method based on high-density gold stud bump bonding of silicon die on microcable has been developed. We present the Cu microcable design, capacitance simulations and measurements together with the individual steps performed in the STS detector assembly.