Temperature & Humidity Control: Balancing Process Requirements and Human Comfort
Temperature and humidity in clean laboratory construction are primarily determined by process needs, with human comfort as a supplementary consideration. As air cleanliness requirements become more stringent, process-specific temperature and humidity standards have also grown increasingly rigorous. A core trend: finer processing precision demands narrower temperature fluctuation ranges.
Case in Point: Semiconductor Lithography Process
In large-scale integrated circuit (LSI) lithography, the thermal expansion coefficient difference between mask materials (glass) and silicon wafers must be minimized. For a 100μm-diameter silicon wafer, a 1°C temperature rise causes 0.24μm linear expansion-hence a strict constant temperature requirement of ±0.1°C. Humidity control is equally critical:
- Low humidity is preferred to prevent product contamination from human sweat, especially in sodium-sensitive semiconductor workshops (maximum temperature: 25°C).
- Condensation risks rise when relative humidity exceeds 55%, potentially damaging precision equipment or circuits and causing operational accidents.
Pressure Regulation: Preventing Contamination Intrusion
Most cleanrooms require positive internal static pressure relative to the exterior to block external contamination. Pressure difference maintenance adheres to two core principles:
- Clean spaces must have higher pressure than non-clean areas.
- Spaces with higher cleanliness levels must have higher pressure than adjacent lower-level areas.
Pressure difference is sustained by supplying fresh air to compensate for air leakage through gaps. Physically, it acts as resistance against air leakage (or penetration) through the cleanroom's structural gaps.
Air Speed Specifications
Air speed standards vary by cleanroom type (airflow pattern), with additional equipment-specific requirements addressed separately:
Turbulent Flow Cleanrooms
These rely on air dilution to reduce contamination, so "air change rate" is the primary metric rather than direct air speed. Key speed constraints:
- Air outlet velocity should not be excessive-requiring faster attenuation and a wider diffusion angle compared to standard air-conditioned rooms.
- Horizontal airflow velocity (e.g., recirculation speed in side-supply systems) must not exceed 0.2 m/s to avoid resuspending surface particles and causing recontamination.
Laminar Flow Cleanrooms (Parallel-Flow)
Piston-like airflow drives contamination exclusion, making cross-sectional air speed a critical indicator. Historically, the U.S. Federal Standard 209B recommended 0.45 m/s, but energy-saving efforts have spurred exploration of lower velocities.
Chinese National Standards (per Air Cleaning Technology Measures and Cleanroom Design Code):
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Vertical laminar flow cleanrooms: ≥0.25 m/s
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Horizontal laminar flow cleanrooms: ≥0.35 m/s
Noise Control: Ensuring Operational Efficiency and Comfort
Clean laboratory noise standards are stricter than basic health protection requirements, aiming to support normal operations, effective communication, and a safe working environment. Three core evaluation indicators:
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Annoyance Impact
Noise-induced discomfort is categorized into six levels: extremely quiet, very quiet, quiet, slightly noisy, noisy, and extremely noisy. "Noisy" and "extremely noisy" levels trigger high anxiety, measured by the percentage of affected individuals (high anxiety rate).
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Work Efficiency Impact
Noise impairs three key work aspects: concentration, operational accuracy, and task speed.
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Communication Interference
Excessive noise disrupts verbal communication-critical for collaborative operations and emergency responses in laboratories.