Sapphire (α-Al₂O₃) is the preferred substrate material for LED chip manufacturing, with approximately 90% of LED chips using sapphire as the substrate. chromium oxide green (Cr₂O₃), with its hardness similar to sapphire and unique chemo-mechanical polishing characteristics, has become the key abrasive for ultra-precision sapphire substrate machining.
Why Choose chromium oxide green for Sapphire polishing?
Property chromium oxide green Sapphire Matching Advantage Mohs Hardness 8-8.5 9 Similar hardness enables controlled removal Chemical Composition Cr₂O₃ α-Al₂O₃ Both oxides, chemically compatible Crystal Structure Corundum-type Corundum-type Similar structure, controllable interface reaction thermal stability 1000°C+ 2050°C Machining heat does not affect performance
Gel Abrasive Technology Breakthrough
A 2022 study published in MDPI Applied Sciences introduced gel-formed Cr₂O₃ abrasives, solving the abrasive agglomeration problem in traditional hot-pressed wheels:
- Enhanced Dispersibility: Gel process ensures uniform Cr₂O₃ particle dispersion, preventing agglomeration
- Controllable Mechanical Properties: Polyimide resin content adjusts wheel hardness and elasticity
- Superior Machining Results: Gel wheels outperform hot-pressed wheels in sapphire semi-finishing
- Surface Quality: Achieves nanometer-level surface roughness
Chemo-Mechanical Grinding (CMG) Process
Chemo-Mechanical Grinding (CMG) integrates chemical reaction and mechanical grinding into a single advanced machining process:
- Chemical Reaction: Cr₂O₃ undergoes solid-state reaction with sapphire surface, forming softened layer
- Mechanical Removal: Abrasive mechanically removes softened layer, achieving efficient material removal
- Synergistic Effect: Chemical-mechanical synergy enables high-efficiency, high-precision, low-damage machining
Sapphire Substrate polishing Process
Process Step Abrasive/Tool Objective Surface Roughness Rough Grinding Diamond grinding wheel Rapid removal Ra ~1μm Semi-Finishing Cr₂O₃ gel wheel Flatness correction Ra ~100nm Fine polishing Cr₂O₃ polishing slurry Mirror finishing Ra <10nm Ultra-Fine polishing Colloidal SiO₂ Atomic-level smoothness Ra <1nm
VerdeChrome® polishing Grade Products
VerdeChrome® Functional Oxide Series provides Cr₂O₃ products specifically designed for sapphire polishing:
- Ultra-high purity (Cr₂O₃ ≥99.5%), contamination-free
- Narrow particle size distribution (D50 customizable), uniform removal
- Sub-micron to nano-scale particle sizes available
- Gel abrasive formulation technical support
Request polishing grade samples for sapphire machining solutions.
Reference: Fabrication and Characterization of Gel-Forming Cr2O3 Abrasive Tools for Sapphire Substrate polishing, Applied Sciences, MDPI, 2022
