Tag Archives: Class 100 anti-static wipes

Techniques for Anti-Static Wipes in Class 100 Cleanrooms

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Class 100 cleanrooms (ISO Class 3)—critical for semiconductor, aerospace, and precision optics manufacturing—demand ultra-low particle counts (≤100 particles ≥0.5μm per cubic foot) and strict electrostatic discharge (ESD) control. Anti-static cleanroom wipes (static-dissipative: 10⁶–10¹⁰ Ω; conductive: 10³–10⁶ Ω) are indispensable here, but their effectiveness depends on tailored usage. Below are key application tips to maintain purity, prevent ESD damage, and optimize workflow.

1. Wipe Selection: Match to Cleanroom Task & ESD Sensitivity

Class 100 operations require wipes that balance anti-static performance, lint control, and solvent compatibility—avoid “one-size-fits-all” choices:
  • For Wafer/Optic Cleaning:

    Choose ultra-low-lint anti-static microfiber wipes (0.1μm fiber diameter) pre-wet with 99.9% electronic-grade IPA. Microfiber traps sub-micron particles (down to 0.1μm) without shedding, while the anti-static treatment keeps surface charge ≤50 V—critical for 3nm semiconductors or AR-coated lenses.

  • For Chamber/Equipment Maintenance:

    Opt for conductive anti-static polyester wipes (10³–10⁶ Ω) for high-ESD-risk tasks (e.g., CVD/PVD chamber cleaning). Conductive fibers rapidly channel static to ground, preventing discharges that damage sensitive tool electronics (e.g., sensor modules).

  • For Dry Dust Removal:

    Use dry anti-static cellulose-polyester blend wipes—the blend’s low-outgassing property avoids contaminating cleanroom air, and anti-static additives prevent dust from reattaching to surfaces (e.g., reticle pods).

  • Tip: Verify wipe certification (e.g., ISO 14644-1 Class 3, ANSI/ESD S20.20) via manufacturer docs—only certified wipes meet Class 100 purity/ESD standards.

2. Wipe Handling: Minimize Particle Generation & ESD Risks

Improper handling can introduce particles or static—follow these rules for Class 100 compliance:
  • Open Wipes in Mini-Environments:

    Retrieve wipes from sealed, Class 100-compatible packaging inside a laminar flow hood or glove box. Tear packaging slowly to avoid generating static (fast motions create charge buildup) and only remove one wipe at a time—exposing multiple wipes to cleanroom air increases particle contamination.

  • Hold Wipes by Edges Only:

    Grip anti-static wipes by their outer edges (not the cleaning surface) to avoid transferring skin oils or fibers. For small wipes (e.g., 2”x2” for reticle cleaning), use plastic-tipped tweezers (grounded to the cleanroom’s earth system) to handle them—eliminates direct contact and ESD transfer.

  • Fold for Multi-Use Coverage:

    Fold wipes into a 4-layer pad to create multiple “clean zones.” Use one layer per surface (e.g., one layer for a wafer chuck, a new layer for a sensor) —this reduces wipe usage by 30–40% and prevents cross-contamination between tasks. Avoid refolding soiled layers inward (traps particles).

3. Cleaning Techniques: Tailored to Class 100 Surfaces

Different surfaces in Class 100 cleanrooms require specific anti-static cleaning methods to preserve purity:
  • Wafer Chucks/Reticles:

    Wipe in slow, linear strokes (parallel to wafer/reticle edges) to avoid pushing particles into precision grooves. For chuck vacuum holes, use a folded wipe strip (1cm wide) and gently dab the opening—never insert the wipe into holes (risk of fiber ingestion).

  • Optical Tools (EUV Lenses, Laser Mirrors):

    Dab, don’t rub: Press the anti-static wipe lightly against the optical surface for 1–2 seconds to lift residue, then lift straight up. Rubbing generates friction (static) and risks scratching coatings—critical for EUV lenses (costing $100k+). Follow with a dry anti-static wipe to blot excess solvent.

  • Equipment Interfaces (USB Ports, Sensor Connectors):

    Use mini anti-static wipes wrapped around a non-metallic probe to clean narrow interfaces. Wipe in a twisting motion to cover all connector pins—ensures no ESD buildup (which causes signal interference) and removes dust that blocks data/ power transfer.

4. Post-Use Practices: Maintain Cleanroom Integrity

Class 100 compliance extends beyond cleaning—proper post-wipe handling prevents recontamination:
  • Dispose of Wipes Immediately:

    Place used anti-static wipes in sealed, Class 100-approved waste bags (labeled “ESD-Safe Waste”) immediately after use. Do not leave wipes on workbenches or tool surfaces—they shed particles over time and can reintroduce contaminants.

  • Validate Post-Clean Conditions:

    After cleaning, use a portable particle counter to verify surface particle counts (≤1 particle ≥0.1μm per ft²) and an ESD field meter to check surface charge (≤50 V). Log results in the cleanroom’s maintenance record—critical for audit compliance (e.g., SEMI S2).

  • Store Wipes Properly:

    Keep unused anti-static wipes in temperature- and humidity-controlled cabinets (20–24°C, 30–50% RH). Extreme conditions degrade anti-static coatings or cause wipes to dry out—rendering them ineffective for Class 100 tasks.

Buyer’s Guide: Anti-Static Wipes for Class 100 Cleanrooms

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Class 100 cleanrooms (per ISO 14644-1, equivalent to ISO Class 5) represent the gold standard for ultra-low-contamination environments—used in semiconductor wafer fabrication (≤5nm processes), medical device manufacturing (e.g., implantable sensors), and aerospace component assembly. In these spaces, even 1 particle (≥0.5μm) per cubic foot of air or a tiny electrostatic discharge (ESD) can ruin high-value products or compromise sterile conditions. Anti-static cleanroom wipes for Class 100 environments are not just “clean”—they must meet rigorous standards for particle control, static dissipation, and material purity. This guide outlines critical criteria to ensure you select wipes that protect your processes, equipment, and products.

1. Prioritize Cleanroom Classification Compliance

Class 100 cleanrooms demand wipes certified to match their strict particle limits—never compromise on this foundational requirement:
  • ISO 14644-1 Class 5 Certification: Verify the wipe manufacturer provides third-party testing reports confirming compliance with ISO Class 5 (the international equivalent of Class 100). This ensures the wipe releases ≤10 particles (≥0.1μm) and ≤1 particle (≥0.5μm) per wipe during use—critical for avoiding particle-induced defects in semiconductors or medical devices.
  • Non-Shedding Material: Choose wipes made from ultra-low-linting substrates like 100% continuous-filament polyester or polypropylene. Avoid blended fibers (e.g., polyester-cotton) or staple-filament materials—these shed microfibers that can float in Class 100 air and contaminate surfaces. Test for linting by wiping a black, non-abrasive surface and inspecting for visible fibers under 10x magnification.

2. Validate Anti-Static Performance (Non-Negotiable for ESD-Sensitive Environments)

ESD is a silent risk in Class 100 cleanrooms—static charges can attract particles or damage ESD-sensitive components (e.g., wafer sensors, microchips). Evaluate wipes on these metrics:
  • Surface Resistance Range: Select wipes with surface resistance between 10⁶–10¹¹ Ω (per ANSI/ESD S20.20 standards). This “static-dissipative” range ensures charges are safely grounded without creating electrical arcs. Avoid “conductive” wipes (resistance <10⁶ Ω) for general use—they may cause unintended electrical pathways in delicate equipment.
  • Static Decay Time: Confirm the wipe’s static decay time (time to reduce a 5000V charge to <50V) is ≤2 seconds. Slow decay allows static to linger, increasing particle attraction. Ask manufacturers for IEC 61340-5-1 test data to validate this performance.
  • Anti-Static Treatment Durability: Ensure the anti-static coating is “permanent” (not just a surface spray). Wipes for Class 100 cleanrooms should retain their static-dissipative properties through multiple uses (if reusable) or during storage (for single-use options). Avoid wipes where anti-static efficacy degrades with humidity or time.

3. Match Wipe Type to Class 100 Cleaning Tasks

Class 100 cleanrooms require targeted cleaning—choose wipe formats and formulations based on your specific needs:
  • Dry Wipes: Ideal for removing loose, dry particles (e.g., dust on wafer chucks, lithography tool exteriors). Opt for dry wipes with a dense, smooth texture—this traps particles instead of pushing them around. Use dry wipes first before wet cleaning to avoid embedding particles into surfaces.
  • Pre-Wet Wipes: For removing oils, flux residues, or fingerprints (common in electronics manufacturing), select pre-wet wipes with high-purity solvents:
    • IPA (Isopropyl Alcohol) Wipes: Use 99.9% pure IPA (for oil-free surfaces) or 70% IPA + 30% deionized (DI) water (for better residue dissolution). Ensure the IPA is “semiconductor-grade” (≤10ppb impurities) to avoid trace chemical contamination.
    • Residue-Free Disinfectant Wipes: For sterile Class 100 environments (e.g., medical device labs), choose wipes with hydrogen peroxide (3%) or peracetic acid formulations—these disinfect without leaving toxic or particulate residues.
  • Size and Thickness: Select smaller wipes (e.g., 4”x4”) for precision tasks (e.g., cleaning around microchips) to reduce waste and avoid over-wiping. Thicker wipes (≥80gsm) offer better durability—critical for avoiding tearing (which releases particles) during use.

4. Evaluate Manufacturing and Packaging Quality

Even the best wipe material can be compromised by poor manufacturing or packaging:
  • Cleanroom-Grade Production: Ensure wipes are manufactured in an ISO Class 5 (or better) facility. This prevents pre-use contamination from the factory floor. Ask for a “Certificate of Analysis (CoA)” with each batch, detailing particle counts and static performance.
  • Sealed, Anti-Static Packaging: Wipes should arrive in airtight, static-shielding packaging (e.g., foil-lined bags with resealable zippers). Once opened, store wipes in a Class 100-compatible dispenser with a dust-tight lid—exposure to non-Class 100 air will contaminate the wipes.
  • Shelf-Life and Storage Conditions: Check the manufacturer’s shelf-life (typically 12–24 months for pre-wet wipes). Store wipes in a cool (15–25°C), dry (30–50% RH) area—extreme temperatures or humidity degrade anti-static treatments and solvent purity.

5. Avoid Common Pitfalls

  • Don’t Sacrifice Quality for Cost: Cheaper wipes may skip Class 100 certification or use low-grade materials—costly defects from contamination will far outweigh initial savings.
  • Don’t Reuse Single-Use Wipes: Single-use Class 100 wipes are designed for one pass—reusing them traps particles and degrades anti-static performance.
  • Don’t Overlook Compatibility: Test wipes on a small, non-critical surface (e.g., a spare wafer or equipment part) to ensure they don’t damage coatings (e.g., anti-reflective lens coatings) or plastics.
By following these criteria, you’ll select anti-static cleanroom wipes that not only meet Class 100 standards but also protect your high-value processes from contamination and ESD—ultimately reducing defects, minimizing downtime, and ensuring regulatory compliance.