The temperature and humidity of a clean room are mainly determined based on the requirements of the processing technology. When meeting the conditions of the processing technology, the first choice should be to consider human comfort. With the improvement of air cleanliness requirements, the requirements for temperature and humidity in the process are also increasing, reaching a certain temperature and humidity. For example, in the lithography and exposure process of large-scale integrated circuit production, the difference between the coefficient of thermal expansion of glass and silicon wafer as the mask plate material is becoming smaller and smaller. A silicon wafer with a diameter of 100um causes a linear expansion of 0.24um when the temperature rises by 1 degree, resulting in a constant temperature of ± 0.1 degrees. At the same time, it requires a relatively low humidity value, as sweating can contaminate the product, especially in sodium semiconductor workshops, which should not exceed 25 degrees. (Purification Engineering)
Excessive humidity can cause many problems. When the relative humidity exceeds 55%, condensation can form on the cooling water pipe wall. If it occurs in precision devices or circuits, it can cause various accidents. When the relative humidity is 50%, it is easy to rust. So what are the specific measures for controlling temperature and humidity in purification engineering? Below are several methods for controlling humidity listed by Keruite Purification Technology Co., Ltd. (Purification Engineering)
For most clean spaces, in order to prevent external pollution from invading, it is necessary to maintain the internal pressure (static pressure) higher than the external pressure (static pressure). The maintenance of pressure difference should generally comply with the following principles:
1. The pressure in spaces with high cleanliness is higher than that in adjacent spaces with low cleanliness.
2. The doors between the interconnected clean room projects should open towards rooms with high cleanliness.
3. The pressure in the Shanghai air shower room in clean spaces should be higher than that in non clean spaces.
The maintenance of pressure difference depends on the amount of fresh air, which should be able to compensate for the air leakage from the gap under this pressure difference. So the physical meaning of pressure difference is the resistance of air leakage (or infiltration) through various gaps in the clean room. (Purification layer)
For turbulent clean rooms, the concept of air change frequency is mainly used to reduce indoor pollution due to the dilution effect of air, rather than directly using the concept of speed. However, there are also the following requirements for indoor airflow speed:
1. The airflow velocity at the outlet of the air supply outlet should not be too high. Compared with a purely air-conditioned room, it is required to have a faster speed attenuation and a larger diffusion angle.
2. The airflow speed (such as the reflux speed during side feeding) should not be too high when blowing over the horizontal plane to avoid surface particles returning to the airflow and causing further pollution. This speed should generally not be too high at 0.2m/s.