Basic knowledge about IS0 14644cleanroom factory

• Purpose

To establish and unify the basic understanding of clean workshop and controlled environment within the factory, clarify the core requirements and management principles of the ISO 14644 series of international standards, ensure that all relevant personnel have a clear and consistent understanding of cleanliness level, testing method and continuous monitoring requirements, and provide a fundamental basis for planning, operation and management of cleanrooms.

• Range

This basic is applicable to all clean workshop, clean area and related controlled environment designed, constructed, operated and monitored in accordance with the ISO 14644 standard. It covers all relevant engineering, operation, production and quality assurance personnel.

• Definition and core principle of cleanroom

Definition: A room that reduces the introduction, generation and retention of airborne particles by controlling the concentration of suspended particles in the air, and appropriately regulating parameters such as temperature, humidity and pressure. All other parameters within the room, such as air speed and flow type, vibration, noise, illuminance and static electricity, are all controlled as per the requirements.

Core principle:

Supply the filtered air: Constantly supplying clean air through a HEPA filter or ULPA filter to dilute and removes the pollutants generated indoors.

Air flow: Using specific airflow patterns—such as unidirectional or turbulent flow—ensures effective removal of pollutants.

Differential pressure control: Maintaining positive or negative pressure in the clean room relative to adjacent areas to prevent contamination from entering through doors, windows, or gaps.

Material and Personnel Control: Implementing strict purification procedures for the materials, equipment and personnel entering the cleanroom, and control the sources of contamination.

• Cleanliness level standard

ISO 14644-1 classifies cleanliness levels based on the concentration of suspended particles in the air. The grade is denoted as "ISO Class N", where N ranges from 1 to 9 as an integer. ISO Class 1 indicates the highest level of cleanliness, while ISO Class 9 represents the lowest level.

Key concept:

Particle size threshold: For example, 0.1 μm, 0.3 μm, 0.5 μm, 1.0 μm, 5.0 μm. The grade definition is based on one or more selected particle sizes.

Maximum allowable concentration limit: For each grade, there is a different maximum concentration limit for particles of a specific size (unit: particles/m³).

• • ISO 14644-1Cleanroom grade:

Establish a classification standard for the concentration of suspended particles in the air, using a dual system of imperial units (≥ 0.1 μm particles per cubic foot) and metric units (≥ 0.1 μm particles per cubic meter)

For instance, typical applications in the semiconductor industry:

Class 1: Grade 1 cleanroom (≤35.2 particle/m³)

Class 10: Grade 10 cleanroom (≤352 particle/m³)

Class 100: Grade 100 cleanroom (≤3520 particle/m³)

Class 1000: Grade 1000 cleanroom (≤35200 particle/m³)

Dynamic monitoring requirements: Key areas need to monitor particle concentration in real time. When the concentration exceeds the limit, an automatic alarm should be triggered.

• • ISO 14644-1Cleanroom monitoring requirements: testing method, monitoring frequency, data recording and report.

Key requirements:

Calculation of the number of sampling points: According to the area, the formula is N = A^0.5.

Sampling quantities: each point ≥1L, sampling time ≥1minute

Monitoring frequency: once per shift in the production area, once per week in the non-production area

• • ISO 14644-3: Design and Construction Specifications

Key requirements:

Air tightness: all the gaps less than 0.5mm and are treated with special sealant.

Material: thickness of wall and ceiling steel are more than 50mm; thickness of ground epoxy resin≥3mm.

Differential pressure control: The differential pressure between clean area and non-clean area is more than 10Pa. The differential pressure in different cleanliness level is more than 5Pa.

Air flow: The air speed in the Unidirectional flow cleanroom is 0.36-0.54m/s; the air changing time Non-unidirectional airflow cleanroom is more 15times/h.

• • ISO 14644-4: Device Specifications

Filtration system: The efficiency of HEPA filter is more 99.99%@0.3μm; the efficiency of ULPA filter is more 99.9995%@0.12μm.

Temperature and humidity control: The temperature is 22±1℃. The humidity is 45±5%RH(Semiconductor lithography area).

Vibration control: The Vibration speed in the precision device area is less than 0.5mm/s.

• Main testing and monitoring method:

To prove and maintain the cleanliness level, you need to conduct the following key tests:

Particle concentration test: Measuring at the designated sampling points using discrete particle counters is the core method for verifying the cleanliness level.

Air flow test: Conducting wind speed tests (for unidirectional flow) and air volume tests (for non-unidirectional flow) ensures adequate air flow replacement capacity.

Differential pressure test: measuring the static differential pressure between the cleanroom and adjacent areas ensures the airflow direction is right.

Filter leakage test: Scrubbing the HEPA/ULPA filter and its frame ensures that there is no leakage.