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What is a cleanroom? How are cleanrooms classified?

2026-06-05
Latest company news about What is a cleanroom? How are cleanrooms classified?
Clean Room, also known as dust-free room, forms the foundation of contamination control. Mass production of contamination-sensitive components cannot be realized without cleanroom facilities. As specified in FED-STD-2, a cleanroom refers to an enclosed space equipped with air filtration, air distribution, air conditioning optimization, specialized construction materials and auxiliary fixtures; standardized operational protocols are implemented to regulate airborne particulate concentration for qualifying required cleanliness grades.

A cleanroom is a specially engineered enclosure that eliminates airborne contaminants including microparticles, hazardous gas and bacteria within a defined space. It precisely maintains indoor parameters such as temperature, cleanliness, static pressure, airflow velocity & layout, noise, vibration, illumination and static electricity within preset target ranges. Regardless of fluctuations in ambient outdoor air conditions, the interior consistently retains pre-set cleanliness, temperature, humidity and pressure specifications.

Its core function is stabilizing cleanliness, temperature and humidity of ambient air surrounding manufactured goods like silicon chips, enabling production inside a controlled favorable environment, namely the cleanroom. Per global industrial norms, cleanroom classification is quantified by the count of oversized particles per cubic meter of air. “Dust-free” does not mean complete absence of dust but limits particulate content to an extremely low threshold. Such permitted particles are far finer than ordinary dust, yet even trace dust can severely impair precision optical components, hence dust-free environment is mandatory for optical product manufacturing.

Class A international cleanroom standard restricts particles below 0.5μm to fewer than 3,500 pieces per cubic meter. Chip fabrication adopts stricter criteria exceeding Class A, widely applied for high-end wafer manufacturing. With particulate count capped under 1,000 pieces per cubic meter, this stringent benchmark is commonly named Class 1K across the industry.

Three Main Application States of Cleanrooms

  1. As-built Cleanroom
    A fully constructed and ready-to-operate cleanroom facility complete with all supporting utilities and functional systems, yet no process equipment is installed inside the space.
  2. At-rest Cleanroom
    A fully fitted cleanroom with all equipment installed and calibrated for scheduled operation or in standby status; no operating staff is present within the enclosure.
  3. Operational Cleanroom
    A fully functional cleanroom in regular service with installed production equipment and on-site working personnel, available for full routine manufacturing operations as required.
    Controlled Items
    1. Remove suspended particulate dust floating in ambient air
    2. Inhibit the generation of new particulate contaminants
    3. Precise regulation of indoor temperature and relative humidity
    4. Adjustable control of indoor static pressure differential
    5. Effective exhaust of harmful gaseous pollutants
    6. Ensure airtight sealing for building structures and partitions
    7. Prevention and elimination of static electricity buildup
    8. Suppression of external electromagnetic interference
    9. Comprehensive compliance with site safety specifications
    10. Optimized structural design for energy conservation

    Three Airflow Types: Turbulent Flow, Laminar Flow & Mixed Type | Importance of Airflow & Wind Speed Control Factors

    1. Turbulent Flow Cleanroom

    Fresh air passes through air handling units, ductwork and indoor HEPA filters before entering the room; return air drains via partition side walls or raised access flooring. Air flows irregularly with eddies instead of straight paths, suited for Class 1,000 ~ 100,000 cleanroom standards.
    Definition: A cleanroom with uneven, non-parallel supply airflow accompanied by recirculation and vortex currents.

    Working Principle: Indoor contaminants get diluted continuously by incoming conditioned air to achieve target cleanliness, commonly designed between Class 1,000 and Class 300,000.

    Features: Cleanliness is realized through frequent air changes; higher air change rates deliver superior cleanliness grades.

    (1) Recovery Time: Duration from initial air supply until indoor particle concentration hits designed cleanliness.
    • Class 1,000: Max 20 min (calculated at 15 min)
    • Class 10,000: Max 30 min (calculated at 25 min)
    • Class 100,000: Max 40 min (calculated at 30 min)

      (2) Recommended Air Change Rates (per recovery criteria):
    • Class 1,000: 43.5~55.3 times/hour, standard value 50 times/h
    • Class 10,000: 23.8~28.6 times/hour, standard value 25 times/h
    • Class 100,000:14.4~19.2 times/hour, standard value 15 times/h
    Advantages: Simple framework, low construction cost and easy space expansion; can pair with clean benches to upgrade local cleanliness.

    Disadvantages: Suspended dust stays trapped indoors by turbulent air and easily contaminates manufactured goods; lengthy recovery period to regain cleanliness after system shutdown and restart.

    2. Laminar Flow Cleanroom

    Air flows in uniform straight streams. Full-ceiling filter coverage feeds supply air, with return air extracted via raised floors or side partitions. This design fits high-grade Class 1~Class 100 cleanrooms, split into two categories:

    (1) Horizontal Laminar Flow

    Filtered air blows horizontally toward opposite return walls; pollutants accumulate heavily on downstream areas.
    • Pros: Simple setup and fast operational stabilization after startup.
    • Cons: Higher construction cost and limited room expansion flexibility.

    (2) Vertical Laminar Flow

    Entire ceiling is fitted with ULPA filters for top-down air delivery. Dust from equipment or operators is quickly exhausted without cross-contaminating separate working zones.
    • Pros: Easy daily management, rapid cleanliness stabilization, minimal disturbance from staff or production activities.
    • Cons: High build expense, poor layout flexibility; ceiling suspension frames occupy space and hinder filter replacement maintenance.

    3. Mixed Type Cleanroom

    Combines turbulent and laminar airflow to create ultra-clean localized production zones.

    (1) Clean Tunnel

    HEPA/ULPA filters fully cover processing areas to reach Class 10 or above, cutting setup and running costs. Working areas are isolated from equipment maintenance zones to avoid cross-contamination, widely adopted for ULSI production.
    • Benefits: Flexible capacity expansion and convenient offline equipment maintenance.

    (2) Clean Tube

    Encloses automated production lines with dedicated purification to achieve Class 100+ cleanliness. Isolation separates goods, workers and dust-generating surroundings; low air consumption saves energy, ideal for fully unmanned automated manufacturing.

    (3) Clean Spot (Localized Mini Cleanroom)

    Upgrade core production sections inside Class 10,000~100,000 turbulent cleanrooms up to Class10~1000, including clean benches and mini clean booths:
    • Clean Bench: Class1~Class100 rating.
    • Mini Clean Booth: A compact enclosed space wrapped with anti-static transparent PVC inside turbulent cleanrooms, equipped with independent HEPA/ULPA and air supply units for Class10~1000 cleanliness. Around 2.5m tall, under 10㎡ coverage with four rolling support legs for flexible relocation.

    Core Note: Airflow Importance & Wind Speed Control

    Precise airflow pattern and wind speed regulation dominate cleanliness stability, directly determining particle dilution efficiency, self-purification duration and final cleanroom classification.