Abstract: With the continuous increase of integration of microwave transmitter/receiver (T/R) modules, the signal-channel power of the modules has multiplied. To meet the heat dissipation requirements of high-power T/R modules, research on application of diamond/Cu in T/R modules is conducted in this paper. Ni layers are prepared on the surface of diamond/Cu by palladium-catalyzed reactive process, followed by electroplating gold process. The effect of different Ni plating thicknesses on diamond/Cu solderability and heat dissipation performance is studied. And the low thermal resistance welding process of power amplifier chip is studied. Besides, comparative analysis of the effects of two chip assembly processes (AuSn eutectic soldering and nano-silver sintering) on actual heat dissipation performance of diamond/Cu and MoCu is carried out. The results show that there is no significant difference in heat dissipation performance and solderability of diamond/Cu heat sink with nickel plating thicknesses of 3 μm, 5 μm and 7 μm; the heat dissipation performance of the diamond/Cu power module is significantly impacted by the thickness of the bonding layer; the surface temperature rise of AuSn sample is lower than that of the nano-silver sintering sample; under the heating power of 20 W, when AuSn eutectic soldering is adopted, the maximum surface temperature rise of diamond/Cu is 5.25 ℃ lower than that of MoCu, which means diamond/Cu has more excellent heat dissipation performance than MoCu.