Cleanroom Manufacturing: Class 100 Standards, 7-Stage Ultrasonic Cleaning & Coating Adhesion

In ophthalmic coating facilities, the coating and vacuum deposition bays are operated under ISO 14644-1 Class 5 (Federal Standard 209E Class 100) cleanroom conditions.

In standard outdoor or office air, a cubic meter contains over 35,000,000 particles $\ge 0.5\ \mu$m. Inside an ISO Class 5 cleanroom, ULPA/HEPA laminar filtration systems ensure that a cubic meter contains fewer than 3,520 particles! Technicians enter through air showers wearing static-dissipative antistatic suits, nitrile gloves, and respirators to ensure zero particulate contamination touches the lens blanks.

Before a lens can enter a vacuum coating chamber, it must be stripped of all organic oils, polishing slurry residue, and electrostatic charges through a fully automated 7-stage ultrasonic cleaning line:

1. Stages 1 & 2 (Alkaline Cavitation): Ultrasonic transducers operating at 40 kHz and 80 kHz generate millions of microscopic vacuum cavitation bubbles in heated alkaline surfactant baths ($55^\circ\text{C}$), violently scrubbing away sub-micron grease and organic residues.
2. Stages 3 & 4 (Cascading Deionized Water Rinsing): Lenses are rinsed in ultra-pure deionized (DI) water with electrical resistivity $> 18\ \text{M}\Omega\cdot\text{cm}$.
3. Stage 5 (Ultrasonic Acid Neutralization): A mild organic acid bath neutralizes lingering alkaline surfactants.
4. Stage 6 (Final DI Water Cascade): Ensures zero ionic conductivity residue remains on the surface.
5. Stage 7 (Infrared Vacuum Slow-Pull Drying): Robotic hoists extract lenses from hot DI water at a slow, controlled velocity ($v < 2\text{ mm/s}$), allowing surface tension to pull water away without leaving a single microscopic drying watermark.

Once inside the vacuum chamber, lenses undergo argon/oxygen plasma glow discharge to strip residual moisture and break surface bonds, creating reactive dangling oxygen radicals that bond covalently to the primer layer.

Coating adhesion is verified using the rigorous ASTM D3359 Method B Cross-Hatch Tape Test:

• A multi-blade cutter carves a 100-square grid through the coating.
• Pressure-sensitive industrial tape (3M 600) is firmly applied and rapidly pulled off at a $180^\circ$ angle.
• Under microscope inspection, certified lenses (such as ELLASUV HMC) must exhibit Class 5B rating: 0% coating flaking or detachment, guaranteeing that your coating will never peel over years of daily wear.