Whether assist gas is needed for laser cutting silicon nitride (Si₃N₄) depends on material density and thickness.
1. Application Scenarios
----Porous, low-density Si₃N₄ (8mm): Can be cut with 1kW QCW laser (peak 3kW) using air and specialized parameters; quality is acceptable.
----Dense, hot-pressed Si₃N₄ (8mm): Even with a 10kW peak laser, nitrogen assist is recommended. Air should be avoided.
2. Key Principles
For 8mm thick Si₃N₄, laser cutting involves thermal ablation and gasification. Assist gas plays three crucial roles:
----Remove molten/vaporized residue: High temperatures produce molten Si and SiO₂; without gas, the kerf clogs, causing incomplete cuts or chipping.
----Cool and prevent cracks: Thick boards accumulate high thermal stress; gas carries away heat, preventing fracture and edge chipping.
----Exclude oxygen to avoid oxidation: Air or O₂ forms an oxide layer, blackening the cut, increasing roughness, and reducing strength.
3. Assist Gas Selection
----High-purity nitrogen (N₂, 99.99%): Most common and cost-effective; prevents oxidation, blows away debris, cools, and leaves a clean cut. Pressure: 0.6–0.8 MPa. Suitable for clips, positioning clamps, complex parts, semiconductor, and NEV components.
----High-purity argon (Ar, 99.999%): Inert, smaller heat-affected zone, extremely smooth cuts with almost zero chipping. Ideal for automotive-grade and high-precision substrates but costly.
----Air or O₂ prohibited: Causes blackened cuts, burrs, severe chipping; unacceptable for precision ceramics.
4. Practical Parameters
----Laser type: Fiber laser / UV picosecond
----Assist gas: High-purity N₂, 0.7MPa
----Power: Fiber laser 500–1000W
----Cutting method: Layered ring cutting, 3–4 passes to prevent cracking
----Focus: Negative focus (below the material surface) ensures uniform kerf
YCLaser provides laser processing for various hard and brittle materials, including free sampling and process optimization. Contact us for a customized solution.
