Cleanroom wipes look simple, but their performance depends on one core factor: cleanliness.
For industries working at micron or nanometer scale, any loose fiber or airborne particle can affect yield, stability, or contamination control. Three parameters matter most: fiber release, liquid-borne particles (LPC), and the Helmke Drum test.
Why Cleanliness Is the Most Critical Indicator
Cleanroom wipes are used after the main cleaning processes. They must not introduce new contaminants.
A wipe’s cleanliness defines how many particles or fibers it releases during use—on surfaces, in liquid, and into the air.
Cleanliness directly impacts:
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Optical precision
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Biological sample integrity
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Chip yield
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Surface finish quality
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Equipment uptime
If a wipe sheds fibers or particles, cleaning becomes counter-productive. This is why most semiconductor, optics, and biotech workflows specify cleanliness levels before material, size, or absorbency.
Fiber Release ≥100 µm: Why It Matters for Optics and Bio-Applications
Fibers ≥100 µm are large enough to be seen under standard magnification and can interfere with alignment, imaging, or biological purity.
They are usually measured as fiber count per wipe using optical inspection.
Why Large Fibers Are Critical
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Optical industry：Long fibers can scratch coated lenses, interfere with laser paths, or remain trapped in fine mechanical gaps.
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Biotech and pharmaceuticals：Fibers can compromise sterility testing, settle in culture plates, or cause false positives.
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Precision assembly：Fibers can block micro-valves, sensors, or fluidic channels.
Typical Fiber Levels by Material
| Material Type | Typical Fiber Level (≥100 µm) | Notes |
|---|---|---|
| Polyester knit | Very low | Most suitable for Class 100/ISO 5 |
| Polyester/cellulose | Moderate | Good for Class 1000/ISO 6–7 |
| Polypropylene nonwoven | Low–moderate | Depends on bonding method |
| Cotton or rayon | High | Not recommended for cleanrooms |
A wipe with high long-fiber counts should not be used in optical assembly or critical biological sampling.
Liquid-Borne Particles ≥0.5 µm: Real Risks for Semiconductor Processes
For semiconductor and microelectronics, liquid-borne particles (LPC) are more harmful than fibers.
Particles ≥0.5 µm can attach to wafers, create defects, or reduce yield during cleaning steps involving IPA or DI water.
LPC is measured by rinsing wipes and analyzing particle size distribution.
Why Particles ≥0.5 µm Matter
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Many logic and memory devices tolerate <100 nm contamination levels.
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Particles in the 0.5–5 µm range are large enough to cause killer defects.
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Residues left on stainless steel tools or chambers accumulate and increase downtime.
Typical LPC Ranges
| Wipe Type | ≥0.5 µm LPC (Particles/cm²) | Suitable Cleanroom Level |
|---|---|---|
| Polyester knit (sealed edge) | Very low | Class 100 / ISO 5 |
| Meltblown PP | Low–moderate | ISO 6–7 |
| Poly-cellulose | Moderate–high | ISO 7–8 |
| Cotton | Very high | Not for cleanrooms |
In semiconductor fabs, LPC is often a top-three decision factor, along with absorbency and ionic contamination.
Helmke Drum: Airborne Shedding Under Motion
The Helmke Drum test measures airborne particles released during movement, simulating real wipe handling.
The result is expressed as particles per cubic foot (≥0.3 µm or ≥0.5 µm).
This parameter tells you whether a wipe can be safely used in Class 100 / ISO 5 environments, where airflow speed and turbulence can lift loose fibers into the air.
Why the Helmke Test Decides Class-Level Compatibility
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In Class 100 zones, airborne particles are the biggest contamination threat.
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Even a clean surface wipe can fail if it sheds particles when shaken.
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Helmke performance separates true cleanroom wipes from industrial nonwovens.
General Classification by Helmke Category
| Helmke Category | Particle Release | Cleanroom Level |
|---|---|---|
| Category I | Lowest | Suitable for Class 100 / ISO 5 |
| Category II | Low | ISO 6–7 |
| Category III | Moderate–high | ISO 7–8 |
If a wipe does not pass Category I, it should not be used in ISO 5 critical cleaning.
Which Industry Should Focus on Which Metric?
| Industry | Most Critical Metric | Why |
|---|---|---|
| Semiconductor / IC Fab | LPC ≥0.5 µm + Helmke | Affects yield and airborne stability |
| Optics / Laser / Photonics | Fibers ≥100 µm | Fibers scratch or distort optical paths |
| Biotech / Pharma | Fibers + LPC | Avoid cross-contamination and test deviation |
| Precision Machinery | LPC | Clean metal surfaces need low residue |
| Laboratories / R&D | Balanced | Depends on experiment requirements |
Different workflows prioritize different contamination types. There is no universal best wipe—only the right wipe for the right environment.
How to Evaluate Data Without Being Misled
Cleanroom wipe data sheets vary between suppliers. Some show average values; others display best-case results.
Follow these steps to avoid marketing bias:
1. Compare measurement methods
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LPC: Was it tested in DI water or IPA?
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Fiber count: Microscopy or automated inspection?
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Helmke: Category or raw particle numbers?
Ensure you compare data measured under the same conditions.
2. Check edge type
Laser-sealed edges release fewer particles than ultrasonic or cold-cut edges.
3. Look at variance, not only the mean
A wipe with low average but high variance may cause unstable performance.
4. Review cleanroom compatibility
If a wipe claims ISO 5 compatibility, it must show Helmke Category I data—otherwise, the claim is incomplete.
5. Beware of “too perfect” numbers
If all particle counts are unrealistically low, the supplier may be quoting only lab-optimized samples, not real production output.
6. Request batch-specific COA
Real cleanroom operations rely on traceable quality, not brochure data.
