77GHz radar substrates demand ultra-low loss, stable Dk at mm-waves, high thermal conductivity, and excellent dimensional stability to minimize signal attenuation and ensure antenna/transceiver performance. Standard FR-4 is unsuitable (Df≈0.02, loss≈30%/m at 77GHz), while low-frequency materials (e.g., RO4350B) struggle with Dk drift at mm-waves. The gold standard for 77GHz radar is Rogers RO3003, with RT/duroid 5880, RO4003C, and specialized PTFE-ceramic composites as alternatives.

Rogers RO3003 (the most widely used) is a ceramic-filled PTFE laminate with Dk=3.00@10GHz, Dk=3.07@77GHz, Df=0.0013@10GHz, and ultra-low copper roughness (VLP ED copper, Ra≤1μm). It offers excellent Dk stability (±0.05 from -40°C to 125°C), low moisture absorption (≤0.06%), and high thermal conductivity (0.5 W/m·K), critical for 77GHz signal integrity and heat dissipation in automotive ADAS. Its mechanical uniformity enables reliable multilayer designs without warpage, supporting complex antenna arrays and transceivers.

Rogers RT/duroid 5880 (Dk=2.2, Df=0.0009@10GHz) is ideal for long-range 77GHz radar requiring minimal loss, though higher cost limits mass deployment. RO4003C (Dk=3.38, Df=0.0027@10GHz) offers a cost-performance balance for mid-range radar, with lower loss than FR-4 but higher than RO3003.

Other options include Sumitomo Electric fluororesin substrates (low loss, smooth copper, 4dB/100mm loss reduction vs conventional materials) and Resonac MCL-LW-990(RFD) (high adhesion, reliability, and wiring accuracy for automotive-grade 77GHz radar).

Key selection criteria for 77GHz radar: Dk 2.2–3.1 (stable over frequency/temperature), Df ≤0.0015@10GHz, low copper roughness, high thermal conductivity, and automotive reliability (AEC-Q100). These materials ensure minimal signal attenuation, precise impedance matching, and long-term stability in harsh automotive environments, enabling accurate detection (up to 300m) and high-resolution imaging for autonomous driving.