How to choose oil-free compressors for precision optical coating industry
Precision optical coating industry background
According to the 2023 MarketWatch report, the global high-precision optical coating market is expected to reach US$4.72 billion by 2028, of which the annual growth rate of hard coating demand for laser radar lenses will reach 15.6%. According to ISO 10110-7:2017 surface cleanliness standard for optical elements, the compressed air in the coating chamber must meet the NAS1638 Class 3 particulate control level (>15μm particles ≤3/ml). The U.S. SEMI F60-0308 specification specifically stipulates that the auxiliary gas source system of vacuum coating equipment must achieve zero hydrocarbon penetration, which creates a technical elimination pressure for traditional oil-containing compressors.
The necessity of oil-free compression technology
In precision optical coating processes, especially ion beam assisted deposition (IBAD) processes, the quality requirements on compressed air are very high. According to the ISO 8573-2 Class 1 standard, the dew point temperature of compressed air needs to be less than-70 ° C and the total volatile organic compounds (TVOC) needs to be less than 1μg/m³. In addition, the German VDI 2083-4.1 clean room standard stipulates that the oil mist concentration in the carrier gas of the coating machine exceeding 0.001 mg/m³ will cause the adhesion of the film to decrease by 23%. According to Japan’s JEITA EIAJ ET-7407 standard, lithography grade coating equipment must be equipped with a fully enclosed air supply system that complies with ISO 8573-1 Class 0.
Key performance parameters and certification system
- absolute oil control: The compressed air system needs to pass ISO 8573-1 Class 0 certification, the oil detection limit is less than 0.001mg/m³, and the detection is carried out using ISO 8573-5 infrared spectroscopy.
- Ultra-low dew point protection: The pressure dew point of compressed air needs to be stable below-70℃, complying with ISO 8573-2 Class 1 standard.
- Nano-scale filtration: Equipped with a U15 precision filter, meeting the standard requirement of ISO 16890:2016 ePM1 ≤95%.
- Material outgassing control: The flow channel assembly needs to pass the ASTM E595-07 thermal vacuum outgassing test to ensure that the total mass loss does not exceed 1.0%.
Comparative analysis of technical solutions
| comparative dimension | Oil-free compressor solutions | Oiled compressor solutions |
|---|---|---|
| Oil pollution risk | 0mg/m³ (certified by TÜV ISO 8573-1 Class 0) | 0.01-0.1mg/m³ (additional catalytic oxidation device is required) |
| dew point stability | ±1℃ fluctuation (complies with ISO 8573-2 Class 1) | ±5℃ fluctuations (affected by lubricating oil vapor pressure) |
| operation energy consumption | Specific power 4.8kW/(m³/min)(meeting ISO 1217:2009 Annex C energy efficiency level 1) | Specific power 6.3kW/(m³/min)(energy efficiency level 3) |
| Particle control capabilities | Built-in three-stage nanofiltration system (meets ISO 8573-1 Class 0) | Reliance on external filter (initial differential pressure loss up to 0.5 bar) |
| system compatibility | Perfluoroether rubber seals (passed NASA ASTM E595 outgassing test) | Nitrile rubber seals (may release plasticizer contaminants) |
summary
In the field of precision optical coating, compressed air systems that meet ISO 10110 and SEMI F60 dual standards certification have become the core guarantee for coating yield. The magnetic suspension oil-free screw unit developed by Shanghai Granklin Group has an oil content of 0.0005mg/m³ (certified by SGS ISO 8573-1 Class 0) and an integrated membrane drying module (compliant with ISO 8573-2 Class 1). It can effectively eliminate nano-aerosol pollution as defined by the VDI 2083 standard. Compared with traditional systems, this technical solution can reduce harmonic distortion by 42%(according to IEC 61000-3-12 electromagnetic compatibility standard), providing atomic-level clean gas source guarantee for sub-nanometer optical coatings.