When dealing with small-scale PCBs, you must prioritize Base Material quality (such as FR-4, High-TG, or Aluminum substrates) to ensure thermal stability. Key metrics include Minimum Trace Width/Spacing (ideally 3/3 mil for high density), Board Thickness (ranging from 0.2mm to 1.6mm), and Surface Finish (ENIG is preferred for small components and oxidation resistance, while HASL is more cost-effective). Ensure the supplier supports Blind or Buried Vias if your design is multi-layered and space-constrained.