Recent Die-to-Die (D2D) interconnects require high data rates operating at high frequencies (> 10 GHz) in multichip packages. Mechanical adhesion was utilized to improve the reliability of traditional packages by increasing interface roughness between epoxy dielectrics and electrochemically deposited copper interconnects. The classical packages, operating at low frequencies below 1 GHz, showed a negligible scattering of electromagnetic waves (S21 < 0.5 dB/m) on the rough surface [1, 2]; however, recent interconnects present considerable degradation in power losses (S21 > 1.0 dB/m) on the rough surface due to skin effect at high frequencies (> 10 GHz) [2]. While previous works have shown the impact of surface roughness on adhesion enhancement, a trade-off between adhesion and power losses has not been precisely considered. This study investigates the trade-off between reliability and performance. We explore the impact of surface roughness on adhesion and power efficiency of electrochemically deposited copper interconnects at high frequencies up to 18 GHz. Wet etching was performed to modify surface roughness for low-cost production. The root-mean-square roughness (RRMS) is regulated at ~10-100 nm to examine smooth copper-epoxy interfaces for future D2D interconnects. The surface morphology is analyzed by atomic force microscopy (AFM). Adhesion and insertion losses are investigated by peel test and vector network analyzer. A direction for future work is provided to improve chemical adhesion at a smooth copper-epoxy interface. Chemical adhesion is expected to improve the reliability of future multichip packages while maintaining power integrity. For example, surface oxidation and silane coupling agents are discussed to improve chemical adhesion at the smooth interface (< 100 nm RRMS).