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Selection principles for FFU in electronic semiconductor clean rooms
2026/4/9
PART 01 Core selection indicators: First, clarify the process requirements
The selection of FFU is not merely based on parameters, but rather deduced from the core demands of semiconductor production. The following four indicators are fundamental.
Dust class matching is the primary prerequisite for selection. Common dust classes in the semiconductor industry range from ISO 1 (Class 1) to ISO 5 (Class 100), with different processes (such as lithography, etching, packaging) having different requirements. For a Class 1 cleanroom, FFUs with high-efficiency filtration efficiency (HEPA H14 or ULPA U15 and above) should be selected to ensure a filtration efficiency of ≥99.999% for 0.1μm particles.
Airflow and pressure calculation: The airflow must meet the "air change rate" requirement of the cleanroom. A Class 100 cleanroom typically requires ≥60 times per hour, and a Class 1 cleanroom requires even higher. The calculation formula is: Required airflow = Cleanroom volume × Air change rate.
The pressure must overcome the resistance of the cleanroom ceiling static pressure box, high-efficiency filter, and air duct. Generally, a 10% - 20% pressure margin should be reserved to prevent airflow reduction during FFU operation.
Operation stability and energy consumption: Semiconductor production often runs continuously for 24 hours. The mean time between failures (MTBF) of FFUs should be ≥50,000 hours. Models with brushless DC motors (BLDC) are preferred as they have lower noise (≤55dB) and longer lifespan.
Energy consumption is a key long-term cost factor. Select FFUs with variable frequency function, which can dynamically adjust the airflow according to the dust class requirements, saving more than 30% energy compared to fixed-frequency models.
Control and monitoring functions: Support centralized control, allowing remote adjustment of airflow and monitoring of operating status (such as fan speed, filter differential pressure) through PLC or IoT systems.
Have fault alarm functions (such as motor overload, filter blockage) to ensure timely response to abnormalities and avoid affecting production.
PART 02 Key component selection: Determining the performance ceiling of FFUs
The core components directly affect the reliability and cleanliness of the FFU. The following three points need to be given special attention.
Filter selection must be in accordance with the standards of the semiconductor industry. HEPA (High Efficiency Particulate Air) filters are suitable for ISO Class 5 and above, while ULPA (Ultra Low Penetration Air) filters are suitable for ISO Class 1 to 4.
Give priority to choosing filters with a "filter material integrity test interface" to facilitate regular scanning tests and ensure there are no leaks.
Fans and Motors: The fan should be a centrifugal fan, which has better uniformity in air distribution compared to axial fans, avoiding local vortices in the clean room. The motor should preferably be a brushless DC motor (BLDC), which is 15% to 20% more efficient than AC motors and offers more precise speed control, ensuring a stable air volume.
Box Structure and Materials: The box material should be 304 stainless steel or galvanized aluminum-zinc steel plate, with a surface roughness of Ra ≤ 1.6 μm, to prevent dust accumulation and corrosion, meeting the cleanliness requirements of the semiconductor industry for materials. The box should have good sealing, with a leakage rate of ≤ 0.1%, to prevent external contaminated air from entering the clean area.
PART 03 Selection Process: Four Steps from Requirements to Implementation
Clarify the process parameters to determine the area, height, target cleanliness level (such as Class 1, Class 100) of the cleanroom, and the requirements for air change rate, and calculate the total air volume required.
Determine the specifications of a single FFU based on the total air volume and the ceiling layout of the cleanroom, and decide on the size of the FFU (such as 1200×600mm, 1200×1200mm) and the air volume of each unit (such as 800m³/h, 1200m³/h).
Screen suppliers and conduct sample tests. Prioritize suppliers with cases in the semiconductor industry, request samples, and perform tests on air volume uniformity, noise, and energy consumption to verify if they meet the requirements.
Formulate installation and maintenance plans. Confirm the installation method of the FFU (such as ceiling-mounted or bracket-mounted), and require the supplier to provide plans for filter replacement cycles and motor maintenance suggestions.
