Reasons of FO Lapping Powder for Thinning Hard and Brittle Optical Substrates
FO lapping powder is a composite abrasive—a blend of aluminum oxide and zirconium silicate—designed for the initial thinning stage. It is not intended for final mirror-finish polishing; rather, it is specifically engineered for the double-sided thinning and parallelism correction of hard, brittle substrates such as IR-cut (blue) glass, optical glass, and various crystals. The key reasons are as follows:
1. Moderate Hardness and Stable Material Removal with Controlled Subsurface Damage
Compared to green silicon carbide (GC)—which is harder and more aggressive, often causing deep cracks or edge chipping—FO lapping powder features softer abrasive edges. It provides a stable material removal rate, effectively eliminating saw marks and reducing thickness while keeping the subsurface damage layer uniform and controlled. This ensures a consistent “allowance” for the subsequent final polishing stage (typically using cerium oxide), leading to higher yields—an ideal characteristic for ultra-thin optical filters.
2. Extremely Narrow Particle Size Distribution with No Oversized Grains, Minimizing Scratch Risks
FO lapping powder undergoes strict classification, ensuring a near-total absence of oversized particles. During batch double-sided grinding, this results in uniform surface patterns and significantly reduces the risk of random, deep scratches. Since optical components have an extremely low tolerance for scratches or pits, this is a primary reason why optical manufacturers prefer FO lapping powder.
3. Composite Formulation Balancing Cutting Power and Surface Uniformity
FO lapping powder is not merely white fused alumina; it is a composite system of aluminum oxide and zirconium silicate. This blend balances grinding efficiency with surface quality, ensuring excellent parallelism and consistent Total Thickness Variation (TTV) after double-sided grinding. It is well-suited for the mass production of IR-cut (blue) glass and other optical glass blanks.
4. Low Impurity Content and Easy Cleanability, Preventing Surface Contamination
FO lapping powder is strictly controlled for iron and heavy-metal impurities, ensuring that abrasive particles do not become embedded in the glass surface. Furthermore, the residual powder is easy to clean off after grinding, preventing defects in subsequent coating or filtering layers—making it fully compatible with the requirements of downstream optical coating processes.
5. FO lapping powder is designed for use with double-sided lapping/polishing machines and offers excellent slurry stability.
FO lapping powder exhibits superior suspension properties, resisting rapid sedimentation. During long-duration, continuous processing, it maintains a consistent material removal rate. It is highly compatible with standard aqueous lapping fluids and dispersants, facilitating the standardization of production line processes.
In summary, FO lapping powder is an alumina-zirconium silicate composite abrasive/polishing powder. It features moderate hardness, a narrow particle size distribution, and strict control over coarse particles. It enables stable material removal and the correction of parallelism while minimizing subsurface damage and the risk of scratching. Furthermore, any residual powder is easily cleaned off. It is ideally suited for the initial double-sided precision lapping of hard, brittle substrates—such as IR filters and optical glass—providing a stable foundation for subsequent mirror-finish polishing with cerium oxide.
Zhengzhou haixu abrasives co.,ltd,now produce the FO Lapping powder which is equivalent to Fujimi FO Lapping Powder,the chemical compostion test report as follows:
Comparasion of PSD(Particle Size Distribution) between ours(AZ) and FUJIMI FO as follows:
