Fire polishing quartz glass is the only proven method to permanently eliminate the hidden sub-surface damage layer (SSD) created by CNC machining. A precisely controlled hydrogen-oxygen flame instantly melts the outer 0.1-0.3mm of the surface and recrystallizes it into a perfect atomic structure — removing micro-cracks, healing all mechanical damage and delivering a mirror finish that stays particle-free even after thousands of 1200℃ thermal cycles. With 25 years of daily production experience on diffusion furnace tubes, DUV windows and photovoltaic crucibles, we have refined every parameter to meet the strictest 2025 cleanliness and damage-threshold requirements. Here is the complete practical guide from our workshop.
Why Fire Polishing Quartz Glass Is the Ultimate Surface Solution
The process uses a high-purity hydrogen-oxygen flame (2500-2800℃) to melt and rapidly recrystallize the surface, erasing mechanical damage in seconds.
Fire Polishing Quartz Glass vs CNC Polishing vs Chemical Polishing
| Item | CNC Polishing | Chemical Polishing | Fire Polishing Quartz Glass |
|---|---|---|---|
| Surface Roughness Ra | 0.5-1.5μm | 0.3-0.8μm | <0.3nm |
| Sub-surface Damage | 50-150μm | 20-50μm | Completely Removed |
| Particle Release (1200℃) | High | Medium | Near Zero |
| 193nm Transmission Gain | Minimal | 0.3-0.8% | 1.5-3.5% |
| Laser Damage Threshold Gain | <20% | 30-60% | 80-200% |
Why Fire Polishing Quartz Glass Became Essential in 2025
12-inch lines demand <3 particles per wafer and 193nm windows require >1J/cm² damage threshold — only this process physically eliminates particle sources at the root.
Core Process Parameters
Every batch is 100% tested with AFM and high-temperature particle counting.
Achievable Surface & Cleanliness Levels
Top-grade fire polishing quartz glass delivers Ra<0.25nm and <0.03 particles/cm² after 1200℃ × 500 cycles.
Sub-surface Healing Depth
Heavy passes heal 150-300μm deep damage, removing even the deepest mechanical cracks.
Internal Grading Standards
| Grade | Ra | Particles (1200℃/500 cycles) | Healing Depth | Typical Use |
|---|---|---|---|---|
| Standard | <0.8nm | <2/cm² | 50μm | General PV/Lab |
| Precision | <0.5nm | <0.5/cm² | 100μm | 8-12 inch tubes |
| Top-tier | <0.3nm | <0.05/cm² | 150-300μm | 193nm windows |
| Extreme | <0.25nm | Near Zero | >300μm | EUV/space optics |
Exclusive Strategies for Different Parts
12-inch Diffusion Furnace Tubes
Inner + outer simultaneous flame, speed 6-12mm/s, 12-18 fine passes for uniform heating without ovality.
193nm/248nm Optical Windows
Double-side flame + 16-point infrared array, speed 2-5mm/s, 15-25 fine passes, temperature stability ±2℃.
Photovoltaic Large Crucibles
Heavy inner polishing, light outer, all edges fully rounded.
Complex Shaped Parts
5-axis flame torch + manual fine-tuning for every dead corner.
Ten Fatal Mistakes That Ruin Results
- Starting on cold parts → instant shattering
- Hydrogen-oxygen ratio drift → bubbling or incomplete healing
- Scan speed too fast → cracks only half-melted
- No preheating on large tubes → 1000℃ temperature shock
- Single-side polishing only → back stress cracks the good side
- No final annealing → delayed self-explosion
- Missing dead corners → hidden particle source
- Insufficient fine passes → Ra still >0.8nm
- Acceptance by eye only → failure discovered on line
- Skipping intermediate annealing → new stress from rough passes
Our Complete Closed-Loop Process
- Incoming AFM full scan & damage mapping
- Overall preheating 800-1000℃ ×4h
- Rough polishing (fast removal of deep damage)
- First intermediate annealing
- Medium polishing stage
- Second precision annealing + LN2 shock test
- Fine polishing (slow, multiple passes)
- Final gradient annealing + multi-stage ultrasonic cleaning
- Cleanroom AFM + particle counting + full report
FAQ – Fire Polishing Quartz Glass
Q1: Can fire polishing quartz glass really achieve near-zero particles?
A: Tested 1200℃ ×1000 cycles <0.03 particles/cm².
Q2: Is fire polishing quartz glass mandatory after CNC?
A: Essential for 193nm windows and 12-inch tubes; optional for structural parts.
Q3: How much material is removed?
A: Fine polishing total <80μm (double side) — leave 0.1-0.15mm allowance.
Q4: Transmission gain on 193nm windows?
A: 2-4% increase, damage threshold 100-200% higher.
Q5: Uniformity on large tube inner surfaces?
A: Inner torch + 4K endoscope + automatic compensation, temperature difference <10℃.
