Clean rooms have real special requirements for air conditioning. Since there are no heat loads in a clean room to deal with, the main focus is on adequate throughput of air, correct temperature, control of humidity and consistent quality of air.
Most products manufactured in clean room surroundings are known to be sensitive to moisture. These control points may range from 35-65 per cent RH for operation all through the year. The levels of RH are usually maintained in a narrow band of about ±2% at temperatures lower than 70 degree Fahrenheit. The impact of higher levels of humidity in close tolerance atmosphere can be damaging to quality of product and schedules of production.
For example, many serious problems may occur due to fluctuations in humidity levels in a wafer fabrication area during the manufacturing of semiconductor. The bake-out time tends to increase and the whole procedure becomes very hard to control. The components may corrode when the humidity levels rise above 35%. When the developer solvents are sprayed on the surface of water, the solvents tend to evaporate at a faster pace and cool the wafer to condense moisture from the air. This additional water may alter the developer characteristics and gets easily absorbed on to the layers of semiconductor. This may result in swelling and affect the quality of the product.
In order to control humidity, an air conditioner is considered to be the best option. Air conditioning units are helpful in lowering the temperature of surfaces that are exposed to the clean room air-stream below the dew point of that specific air-stream. Additional water vapor condenses within the air conditioning system and the resultant air is easily dehumidified.