When evaluating Alumina Ceramic Wafers, the purity level is the most critical factor, typically ranging from 95% to 99.9%. Higher purity (99%+) offers better corrosion resistance and thermal conductivity. You must also specify the surface roughness (Ra); for thin-film applications, a polished surface with Ra < 0.05μm is often required. Additionally, verify the flatness and parallelism tolerances, as these are vital for ensuring proper contact in semiconductor and electronic packaging applications.