Why Thick Stainless Masks Cannot Achieve High-Resolution Micro Patterns
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Limitations of Thick Stainless Masks for High-Resolution Micro-Patterns
Thick stainless steel masks—typically 0.3 mm to 0.5 mm—are widely used for mechanical stability and durability.
However, these masks cannot produce high-resolution micro-scale features (such as 20–50 µm openings) commonly required in semiconductor research, thin-film deposition, and microfabrication.
This page explains the engineering and physical limitations that prevent thick stainless steel from achieving fine-resolution patterns.
Why Thick Masks Cannot Make 25 µm Features
Because the aspect ratio becomes too high.
A clean-cut micro opening must maintain:
Aspect Ratio (thickness : feature size) ≤ 4 : 1
For a 25 µm opening:
- 0.5 mm stainless → AR = 20 : 1 ❌ impossible
- 0.3 mm stainless → AR = 12 : 1 ❌ still impossible
Laser cutting cannot produce a vertical wall at these ratios, causing:
- complete collapse of the cut
- tapered, closed, or blocked openings
- severe heat-affected damage
Aspect Ratio Limit — The Most Important Constraint
| Stainless Thickness | Feature Size Needed for AR ≤ 4:1 | Micro-Pattern Capability |
|---|---|---|
| 0.5 mm | ≥125 µm | No 20–50 µm patterns |
| 0.3 mm | ≥75 µm | Only medium patterns |
| 0.2 mm | ≥50 µm | Acceptable |
| 0.1 mm | ≥25 µm | Best for micro-patterns |
| 0.05 mm | ≥12 µm | Near micro-fabrication limit |
Conclusion:
If the customer wants 25 µm or 30 µm, the mask MUST be 0.05–0.1 mm thick.
Laser Cutting Behavior in Thick Steel
When cutting thick stainless steel:
1. The laser beam diverges inside the metal
→ Creates a taper angle, closing the bottom side of the opening.
2. Heat accumulation melts the micro-feature
→ Burrs, slag, and collapsed geometry.
3. Molten metal resolidifies near the cut
→ Completely blocks narrow openings.
4. Pressure from vaporized metal destabilizes small walls
→ Micro bridges break, holes deform.
These effects increase exponentially as thickness increases.
Mechanical Rigidity Causes Distortion
Thick stainless steel masks are harder and stiffer.
Consequences for micro patterns:
- Small hole walls cannot withstand mechanical stress
- Internal tension during laser cutting warps the feature
- Vibrations cause edge roughness and inconsistency
This is why most R&D-grade micro masks use 0.05–0.15 mm thickness.
Why Thin Masks Perform Better for Micro-Features
1. Low aspect ratio ⇒ Clean laser cut
Laser beam can pass through with minimal taper.
2. Lower heat accumulation
Reduces burrs and deformation.
3. Better alignment to substrate
Thin masks lie flatter → less shadow blur.
4. Ideal for <50 µm features
Thin masks give the best resolution for PVD/CVD/Sputtering.
Recommended Thickness for Common Feature Sizes
| Feature Size | Recommended Thickness | Reason |
|---|---|---|
| 20–30 µm | 0.05–0.10 mm | lowest taper |
| 30–50 µm | 0.10–0.15 mm | best balance |
| ≥100 µm | 0.15–0.20 mm | sturdy enough |
| ≥150 µm | 0.20–0.50 mm | thick masks OK |
Frequently Asked Questions
Q1. Can 0.5 mm stainless steel produce a 25 µm opening?
No — aspect ratio is too high; opening will collapse.
Q2. What is the minimum feature size for 0.3 mm stainless?
≥75–100 µm recommended.
Q3. Why does taper increase with thickness?
The laser beam diverges and loses focus deeper in the metal.
Q4. What thickness is ideal for <50 µm features?
0.05–0.10 mm stainless steel.
Q5. Are thin masks strong enough?
Yes — for micro features in R&D; they can be reinforced if needed.