When selecting a RoHS-compliant PCB, you must prioritize Base Material (Substrate) such as FR-4 (High Tg recommended) for thermal stability. Key parameters include Layer Count (Single, Double, or Multi-layer), Copper Thickness (typically 1oz to 3oz), and Surface Finish. Since lead-based HASL is prohibited under RoHS, you should opt for Lead-Free HASL, ENIG (Electroless Nickel Immersion Gold), or OSP (Organic Solderability Preservatives) to ensure environmental compliance and excellent solderability.