Reasons of Green Silicon Carbide (GC) Micropowder Chosen for Double-Sided Lapping of Optical Master Plates
Objectives of the initial lapping stage for optical master plates: Rapid removal of machining tool marks, correction of flatness, and control of parallelism.
1. Excellent self-sharpening properties, stable cutting, and high efficiency
Green Silicon Carbide (GC) crystals are brittle; during the lapping process, the particles continuously fracture to expose new, sharp cutting edges, preventing the abrasive from becoming dull or “loading” (clogging) the lap plate. Compared to white fused alumina, GC offers a higher material removal rate for the same grit size, making it ideal for the bulk rough and fine shaping of steel or quartz master plates, thereby reducing total processing time.
2. Hardness well-suited for hard and brittle substrates, minimizing large-scale plastic deformation
With a higher hardness than white fused alumina, Green Silicon Carbide (GC) is well-suited for hard, brittle optical master plate materials such as hardened steel or fused silica. It primarily removes material through brittle fracture, allowing for the rapid elimination of lathe tool marks, surface pits, and steps.
3. High thermal conductivity, resulting in lower heat generation and reduced thermal deformation
Optical master plates are extremely sensitive to flatness; heat generation can cause the plate to warp. Green Silicon Carbide possesses superior thermal conductivity compared to white fused alumina, facilitating more efficient heat dissipation. This lowers the risk of thermal deformation and helps maintain the required surface geometry.
4. High chemical stability, preventing rust and surface contamination
Green Silicon Carbide (GC) is chemically inert. Unlike brown fused alumina—which may contain high levels of iron that can leach into wet lapping slurries and cause rust spots on steel master plates—GC does not introduce such contaminants. It leaves minimal residue after cleaning, meeting the stringent cleanliness requirements for optical components.
5. Sharp, angular particles that produce controlled surface patterns
Green Silicon Carbide (GC) creates a uniform, shallow, and fine lapping pattern rather than deep scratches. This consistent texture is easily removed during subsequent polishing or diamond turning processes, ensuring that no deep-seated subsurface damage—which would otherwise be difficult to eliminate—remains. In summary, green silicon carbide is the preferred choice for the double-sided lapping of optical master plates; it offers an optimal balance of material removal rate, self-sharpening characteristics, and thermal conductivity, enabling the rapid correction of flatness and the removal of machining tool marks.