Overview of Cleanroom Standards in Electronics

The air cleanliness level required for integrated circuit manufacturing environments primarily depends on the integration level of the integrated circuits. The air cleanliness levels for different processes are determined based on the probability of potential contamination and the potential for device failure.

For example, in the photolithography process, the silicon wafer is exposed to the production environment, and a high probability of contamination leads to a high defect rate. Therefore, to prevent this hazard, microenvironments are commonly used in cleanrooms for ultra-large-scale integrated circuits. The core process area is isolated, and the required air cleanliness level and environmental control requirements (temperature, relative humidity, and pressure) are achieved within the isolated microenvironment.

ISO Classification & Airflow Parameters

ISO Class Airflow Type Avg Airflow Velocity (m/s) Air Changes/H Application Examples
2 U (Unidirectional) 0.3 ~ 0.5 N/A Photolithography and semiconductor processing area
3 U (Unidirectional) 0.3 ~ 0.5 N/A Work area, semiconductor processing area
4 U (Unidirectional) 0.3 ~ 0.5 N/A Work area, multi-layer mask processing, high-density disk manufacturing
5 U (Unidirectional) 0.2 ~ 0.5 N/A Utility area, multi-story processing area, semiconductor service area
6 M (Mixed) 0.1 ~ 0.3 — Service area, surface treatment
— N/M (Non-U/Mixed) N/A 70 ~ 160 —
7 N/M N/A 30 ~ 70 Service area
8 N/M N/A 10 ~ 20 Service area

ISO Class 6 Cleanroom Core Configuration

This configuration sheet is suitable for a typical ISO 6 production workshop in the electronics industry.

A. Air Purification and Airflow Management System

1. Fan Filter Unit (FFU)

  • Filters: H13/H14 HEPA filters (≥99.97%/99.995% efficiency for 0.3μm).
  • Coverage: 60% - 85% (adjustable based on heat load/layout).
  • Motor: EC motors recommended for energy efficiency.
  • Arrangement: Uniform grid pattern on the ceiling.
Objective: Providing a clean air source and ventilation power is crucial for maintaining cleanliness.

2. Return Air System

  • Main Method: Return air columns or louvers in the lower part of side walls.
  • Optimization: Localized raised flooring (20-30% area) for high airflow areas.
  • Requirement: Unobstructed return airflow with no dead zones.
Objective: Ensures airflow from top to bottom to effectively remove pollutants. Localized raised flooring improves uniformity.

3. Modular Air Handling Unit (AHU)

  • Airflow Rate: Calculated based on 50-70 air changes/hour.
  • Sections: Pre-filter (G4) + Cooling + Heating + Humidifier + Fan + Medium-efficiency (F8/F9).
  • Control: VFD for the fan to respond to indoor load changes.
Objective: Handles fresh air load and most indoor sensible/latent heat loads; provides conditioned air to FFUs.

4. Fresh Air System

  • Type: Independent MAU or integrated into AHU.
  • Pre-treatment: Must include deep dehumidification and chemical filtration.
Objective: Ensure positive indoor pressure and provide fresh air. Deep dehumidification is key for humidity control.

B. Enclosure Structure and Finishing System

Walls and Ceilings

  • Material: Color-coated steel panels (rock wool/magnesium oxide core), ≥50mm thick.
  • Surface: Anti-static, corrosion-resistant, easy to clean.
  • Ceiling: Must support the weight of FFUs.

Ground (Flooring)

  • Options: Anti-static PVC sheet or Epoxy self-leveling flooring.
  • Resistance: 10⁵ - 10⁹ Ω.
  • Requirement: Grounding is required.

Doors and Windows

  • Type: Clean, airtight steel doors (with windows) and aluminum fixed windows.
  • Sealing: Airtightness ensured; door frames fitted with sealing strips.

Other Details

  • Corners: All interior/exterior corners rounded (R≥50mm).
  • Penetrations: All pipe penetrations through walls must be strictly sealed.

Special Configuration Requirements

1. Risk-Based Zoned Air Supply Strategy

  • Work Areas: Ensure sufficient FFU coverage/velocity directly above production lines.
  • Passageways: FFU density can be reduced in passageways/storage areas to save energy.
  • Laminar Flow Hoods: Use ISO 5 hoods in ISO 6 backgrounds for critical spots (e.g., optical inspection).

2. Strict Material and Personnel Management

  • Air Shower: For ≥2 people, wind speed ≥25m/s, time 20-30s.
  • Pass-through: Mechanical interlocking and UV sterilization for materials.
  • Flow Paths: Clear paths to prevent cross-contamination; shoe-changing/lockers at entrance.
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