Green silicon carbide (Green SiC), commonly abbreviated as green silicon or green carbon in the industry, is the core abrasive for precision lapping and polishing of fiber end faces. 4000#, 6000# and 8000# are the most widely used ultrafine powder grades in fiber lapping oil (also known as lapping liquid or lapping paste).
1. Basic Overview
Green Silicon Carbide (GC / Green SiC): Features high purity (SiC ≥ 98.5%~99%), high hardness (Mohs hardness: 9.4), sharp cutting performance and excellent self-sharpening property. It is specially applied to ultra-precision machining of brittle and hard materials such as optical fibers, optical glass and semiconductors.
Mesh Grade (#): Adopts the JIS Japanese standard (widely used domestically). The higher the mesh number, the finer the particle size and the smoother the polished surface.
Fiber Lapping Oil: A blended fluid with green silicon carbide micropowder dispersed in oil-based or water-based medium. It is matched with fiber lapping machines to remove scratches, trim end faces and achieve high-precision polishing.
2. Key Parameters of 4000# / 6000# / 8000# (JIS Standard)
| Specification (JIS#) | Median Particle Size D50 (μm) | Maximum Particle Size D94 (μm) | Fiber Lapping Process | Core Function |
|---|---|---|---|---|
| 4000# | 3.0 ± 0.4 | ≤ 4.0 | Fine Lapping / Semi-Fine Polishing | Remove residual scratches from 9/1μm lapping films and level fiber end faces |
| 6000# | 1.5 ± 0.3 | ≤ 2.5 | Precision Lapping / Pre-Polishing | Conduct in-depth finishing, eliminate micro scratches and reduce surface roughness |
| 8000# | 0.8 ± 0.2 | ≤ 1.5 | Ultra-Fine Polishing / Final Polishing | Achieve mirror-grade finishing with Ra ≤ 0.01μm, scratch-free and pit-free surface |
3. Model Selection & Matching in Fiber Lapping
Standard 4-Step Lapping Process (Common Combination)
- Coarse Lapping: 30μm / 15μm – Remove adhesive burrs and fix end face angles
- Medium Lapping: 9μm / 6μm – Fast material removal and primary surface leveling
- Fine Lapping: 3μm / 1μm or 4000# Green SiC – Transitional finishing and coarse scratch elimination
- Precision & Final Polishing: 6000# to 8000# Green SiC or cerium oxide – Achieve defect-free mirror finishing
Selection Recommendations
- 4000#: Universal fine lapping grade, cost-effective for most SC/LC/FC fiber jumpers
- 6000#: High-end precision lapping grade, ideal for polarization-maintaining fibers, high-power fibers and low-reflection application scenarios
- 8000#: Premium final polishing grade, designed for telecom-grade optical fibers, medical optical fibers and applications requiring ultra-high surface finish
4. Key Purchasing Criteria (Fiber-Grade)
- Purity: SiC content ≥ 99.0%, magnetic impurities ≤ 0.001% to prevent fiber surface scratches
- Particle Size: Compliant with JIS standards with accurate D50 value and narrow particle size distribution (no oversized particles)
- Dispersibility: No precipitation or agglomeration in lapping fluid to ensure uniform polishing performance
- Particle Morphology: Equiaxed or spherical particles to avoid deep micro scratches
5. Common Misconceptions
❌ Green SiC ≠ Black SiC: Black silicon carbide boasts high toughness but low purity, which causes severe scratches and is inapplicable for fiber precision polishing.
❌ Finer grain does not mean better performance: 8000# features low processing efficiency; 4000# combined with 6000# fully meets the demand for commercial standard fiber jumpers.
❌ Standard mixing is prohibited: JIS mesh standard is different from FEPA (F#) standard; JIS standard must be confirmed during procurement.
6. Summary
- 4000#: Core grade for fine lapping with stable and efficient performance
- 6000#: Upgraded quality grade, the mainstream material for precision finishing
- 8000#: Top-tier polishing grade for ultimate surface finish
