Differential Pressure Control in Clean Rooms

The control of pressure difference is the key link to ensure the normal operation of clean room. The appropriate pressure difference can effectively prevent the intrusion of external polluted air and ensure that the air quality in the clean room meets the production or experimental requirements.

Different areas of the clean room have different requirements for cleanliness levels, and reasonable zoning planning is the basis of differential pressure control. For example, in semiconductor manufacturing plants with high cleanliness requirements, the core area of chip manufacturing is often set to the highest cleanliness level, such as ISO1 or ISO2. This area is surrounded by equipment maintenance areas, material transfer areas, etc., and their cleanliness levels are successively reduced, like ISO7 or ISO8. This gradually decreasing clean level layout from the core to the periphery allows air to flow naturally from the high clean area to the low clean area, forming an environment conducive to differential pressure control.

The door and window of the clean room have an important impact on the stability of the pressure difference. The choice of door is crucial, should choose a good sealing material and structure, such as inflatable sealed doors or with double rubber seal translation doors. Do a good sealing treatment between the window frame and the wall, such as using sealing strips to fill the gap, which can reduce the unstable pressure difference caused by air penetration.

The air lock room between the clean room and the unclean area is essential to maintain the pressure difference when people and materials enter and exit the clean room. In a semiconductor clean workshop, personnel enter the air lock room before entering the clean room from the dressing room. The two doors of the lock room cannot be opened at the same time, and by adjusting the pressure in the lock room to make it between the clean room and the outside area, the direct entry of outside air can be effectively reduced, thus helping to maintain the pressure difference in the clean room. At the same time, the air supply and exhaust air of the air lock room should be controlled separately, and the appropriate air exchange frequency should be set according to the actual situation, generally 10-20 times per hour, to ensure that the air lock room can play a good buffer and pressure regulation role in the process of personnel and materials entering and leaving.

For materials entering the clean room, a transfer window can be used. The transfer window is equipped with an interlock device and high efficiency filter. When the external material is put into the transfer window, the outer door is closed. After purification and pressure balance, the inner door is opened and the material is put into the clean room. This method can avoid the large amount of air exchange caused by material entering and leaving and affecting the pressure difference in the clean room.