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Control Technologies of the MAU + FFU + DCC System in Cleanrooms

2024-12-12

In high-end industries such as semiconductor manufacturing, biomedicine, and precision electronics, the control of environmental parameters in cleanrooms directly affects product quality and the reliability of scientific research results. The MAU (Make-up Air Unit) + FFU (Fan Filter Unit) + DCC (Dry Coil Unit) system, as the mainstream air purification solution for cleanrooms, has become a key support for achieving stringent clean environments due to its flexible and efficient control characteristics. This article will delve into the core control technologies of this system, revealing how it creates a stable and precise clean space through multi-dimensional collaborative operations.
I. Overview of the MAU + FFU + DCC System
The MAU + FFU + DCC system is an integrated air treatment and circulation system where each component performs its specific functions while collaborating seamlessly:
MAU is responsible for preprocessing fresh air, including temperature and humidity adjustment, primary filtration, and fresh air supply;
FFU, as the core of end-stage purification, ensures particle control in clean areas through high-efficiency filtration and directional air supply;
DCC precisely regulates indoor sensible heat loads to maintain temperature field uniformity.
This architecture of "fresh air preprocessing + end-stage purification + sensible heat fine-tuning" not only meets the cleanroom's demand for fresh air but also achieves refined management of environmental parameters through hierarchical control, offering better energy efficiency and flexibility compared to traditional centralized air conditioning systems.

II. Key Points of System Control
(I) Temperature Control: Precision Regulation through Multi-module Collaboration
Temperature fluctuations are a critical factor affecting precision manufacturing—for example, in semiconductor lithography processes, a temperature difference of 0.1°C can cause deviations in chip pattern transfer. The MAU + FFU + DCC system achieves micro-level temperature control accuracy through three-level collaborative control:
Basic temperature control by MAU: Adopts an adaptive PID algorithm to dynamically adjust the water flow or refrigerant flow of heating/cooling coils based on real-time temperature feedback in the cleanroom, stabilizing the fresh air temperature within the set range (usually with an accuracy of ±0.5°C);
Indirect regulation by FFU: Although not directly involved in temperature control, its air volume distribution affects indoor air flow organization. By optimizing FFU layout (such as matrix-style uniform arrangement) and wind speed settings (typically 0.3-0.5m/s), local temperature gradients can be reduced;
Sensible heat compensation by DCC: Targeting local heat sources generated by equipment operation (such as lithography machines and bioreactors), real-time offset of sensible heat loads is achieved by adjusting chilled water flow, ensuring that the temperature uniformity error in clean areas is ≤±0.2°C.
Application Case: In the lithography workshop of a 12-inch wafer fab, through the linkage control of MAU and DCC, temperature fluctuations are strictly limited within ±0.1°C, improving chip yield by approximately 3%.
(II) Humidity Control: Balancing Anti-condensation and Process Stability
High humidity can cause equipment corrosion, while low humidity may lead to static electricity—humidity control needs to balance process requirements and equipment protection:
Main adjustment function of MAU: Integrates steam/electrode humidification modules and condensation/rotary dehumidification modules, automatically switching modes based on real-time humidity (with an accuracy of ±2%RH). For example, in pharmaceutical freeze-drying workshops, humidity needs to be stabilized at 30-40%RH to prevent drug moisture absorption;
Auxiliary uniform distribution by FFU: Eliminates local high-humidity areas through air circulation, especially in corner areas of cleanrooms, to avoid microbial growth caused by uneven humidity;
Linkage control logic: When MAU detects that humidity deviates from the set value, it will first adjust fresh air humidity, and DCC will cooperate to reduce the coil surface temperature (needs to be 1-2°C higher than the dew point to prevent condensation), forming a closed-loop control.
(III) Cleanliness Management: Full-process Filtration from Source to End
Cleanliness is the core indicator of cleanrooms, which needs to be achieved through hierarchical filtration and air flow organization:
Preprocessing by MAU: Uses G4 primary and F8 medium-efficiency filters to intercept particles of PM10 and above in fresh air, reducing the load on end-stage filtration;
End-stage purification by FFU: Equipped with HEPA (filtration efficiency ≥99.97% for 0.3μm particles) or ULPA (filtration efficiency ≥99.999% for 0.12μm particles) filters, ensuring that the air supplied to clean areas meets ISO Class 5 (Class 100) or higher standards;
Optimization of air flow organization: Forms vertical unidirectional flow through uniform arrangement of FFUs (coverage rate is usually 60-100%), "pressing out" pollutants from clean areas, and cooperates with return air outlet design to achieve a "piston effect" and avoid air flow dead zones.
Data Reference: In electronic chip cleanrooms, when the operating wind speed of FFUs is stabilized at 0.45m/s, the number of particles ≥0.5μm in each cubic foot of air can be controlled below 35 (meeting ISO Class 5 standards).
(IV) Pressure Control: A Critical Barrier Against Cross-contamination
Pressure gradient is the core for maintaining "unidirectional flow" between clean areas and the outside, as well as between areas with different cleanliness levels:
Fresh air volume adjustment by MAU: Real-time monitoring of pressure differences between clean and non-clean areas (usually 10-30Pa) through differential pressure sensors, and dynamically adjusting fresh air volume in linkage with variable frequency fans to ensure a positive pressure environment (preventing the intrusion of external pollution);
Hierarchical pressure design: A pressure difference of 5-10Pa needs to be set between areas with different cleanliness levels (such as ISO Class 5 and ISO Class 7) to avoid air from low-cleanliness areas entering high-cleanliness areas;
Emergency protection mechanism: When the pressure difference is lower than the set threshold, the system will automatically trigger an audible and visual alarm and start a backup fan to maintain pressure, preventing production interruption.
III. In-depth Application of Intelligent Control Technologies
Traditional cleanroom control relies on manual inspection and manual adjustment, which is difficult to cope with dynamic load changes. The MAU + FFU + DCC system achieves "unmanned" precise management through intelligent upgrading:
Centralized monitoring platform: Based on PLC or DCS systems, integrating more than 30 parameters such as MAU temperature and humidity, FFU operating status, and DCC water flow into the HMI interface, supporting real-time data visualization and historical curve query;
Adaptive adjustment algorithm: When detecting the start or stop of production equipment (such as sudden increase in heat load caused by the start of semiconductor etching machines), the system can automatically adjust MAU coil flow and DCC output within 10 seconds to maintain parameter stability;
Predictive maintenance: By analyzing data such as FFU fan current and filter differential pressure, early warning of equipment failures (such as filter blockage and motor aging) is provided to avoid sudden shutdowns;
Energy consumption optimization: Adopting AI algorithms to dynamically match fresh air volume with indoor load, saving 20-30% energy compared to traditional systems, which is particularly suitable for long-term operation of large cleanrooms.
IV. System Commissioning and Optimization: The Key Step from Qualification to Excellence
A high-quality MAU + FFU + DCC system requires strict commissioning procedures to achieve optimal performance:
Single-machine commissioning
MAU: Test fan frequency conversion range (usually 30-100Hz), initial filter resistance (should be ≤10% of the design value), and temperature and humidity adjustment response speed;
FFU: Inspect each unit for wind speed uniformity (deviation ≤±10%), filter integrity (through scan leak detection), and noise level (should be ≤65dB);
DCC: Verify water flow adjustment accuracy (±5%) and coil heat exchange efficiency.
Linkage commissioning
Simulate extreme working conditions (such as high-temperature and high-humidity weather in summer, full-load operation of equipment) to test and adjust the system's control effects on temperature, humidity, cleanliness, and pressure;
Use precision equipment such as particle counters (minimum detectable particle size 0.1μm) and temperature-humidity data loggers (sampling interval 10s) to record data from over 50 monitoring points in the cleanroom;
Optimize PID parameters (such as proportional coefficient Kp, integral time Ti), and adjust air volume and water flow parameters of MAU, FFU, and DCC to ensure temperature adjustment overshoot ≤0.3℃ and humidity recovery time ≤5min.
Continuous optimization
Establish an energy consumption model based on operating data, dynamically adjusting the number of operating FFUs (20-30% can be shut down under non-full load conditions);
Regularly replace filters (primary filters every 1-3 months, medium-efficiency filters every 6-12 months, high-efficiency filters every 2-3 years) to maintain stable system resistance.
Conclusion: Technology Empowering Clean Manufacturing
The control technology of the MAU + FFU + DCC system is the core support for modern cleanrooms to move from "compliance operation" to "lean management". Through multi-dimensional collaborative control of temperature, humidity, cleanliness, and pressure, combined with in-depth empowerment of intelligent technologies, the system can provide a stable and reliable clean environment for high-end manufacturing and scientific research activities.
As a service provider specializing in cleanroom technology, we always aim for "parameter precision, operational energy efficiency, and management intelligence", providing customers with full-process solutions from system design and equipment selection to commissioning and optimization. If you encounter technical difficulties or have needs in cleanroom environmental control, please feel free to contact us—we will use our professional experience to help your production and scientific research activities reach new heights.