Abstract: With the rapid development of microwave communication systems, computer numerical control (CNC) attenuators are increasingly widely used in the field of phased array radar. CNC attenuators are numerically integrated by cascading small size, high-performance attenuation chips; however, the increased integration density and the decreased chip size have exacerbated the challenge of heat dissipation of these attenuator chips. To address the low thermal resistance requirements for attenuator chip packaging within the DC~6 GHz frequency band, Sn60Pb40, Au80Sn20, Sn96.5Ag3.5 and nano-silver materials are chosen for packaging experiments in this paper; in particular, an innovative vacuum fusion welding and multi-channel exhaust-gas sintering process is employed, the process curves corresponding to different packaging structures are investigated, and a reliable low thermal resistance interconnection between the attenuator chip and the packaging substrate is achieved, hence effectively improving the reliability of chip packaging. The results show that the attenuation chips packaged with nano-silver materials exhibit the lowest thermal resistivity and a significantly reduced heat generation, thereby effectively reducing the impact of heat on chips and improving its reliability in radar system.