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temperature and humidity control in the construction of clean laboratory

Jun 05, 2018

The temperature and humidity of the laboratory construction space are mainly determined according to the process requirements, but the human comfort level should be taken into consideration when meeting the process requirements. With the improvement of the air cleanliness requirements, there has been an increasingly strict demand for the temperature and humidity of the process. The specific process requirements for temperature will be listed later, but as a general principle, due to the increasingly finer processing accuracy, the requirements for the temperature fluctuation range are getting smaller and smaller.

 

   For example, in the lithography exposure process of large-scale integrated circuit production, the difference in thermal expansion coefficient between the glass and the silicon wafer as a mask material is required to be smaller and smaller. 100 um diameter silicon wafer, the temperature rise of 1 degree, it caused a linear expansion of 0.24um, it must have a constant temperature of ± 0.1 degrees, while the required humidity value is generally lower, because people sweat, the product will be polluted, in particular Is afraid of sodium semiconductor workshop, this workshop temperature should not exceed 25 degrees, the problem of excessive humidity generated more problems. When the relative humidity exceeds 55%, condensation will form on the cooling water pipe wall. If it occurs in a precision device or circuit, it will cause various accidents.

Pressure regulations

For most clean rooms, it is necessary to maintain the internal pressure (static pressure) higher than the external pressure (static pressure) in order to prevent intrusion of external contamination. The maintenance of pressure difference should generally meet the following principles:

1. The pressure of clean space is higher than the pressure of non-clean space.

2. The pressure of the high cleanliness level is higher than the pressure of the adjacent low cleanliness level.

The maintenance of the pressure difference depends on the amount of fresh air that can compensate for the amount of air leaking from the gap under this pressure difference. So the physical meaning of the pressure difference is the resistance to leakage (or penetration) when the air volume passes through various gaps in the clean room.


Air speed regulations in the clean room


The airflow speed to be discussed here refers to the airflow speed in the cleanroom. The airflow speed in other cleanrooms is discussed when discussing specific equipment.

For the turbulent clean room Because the main rely mainly on the dilution of the air to reduce the degree of indoor pollution, the concept of the number of air changes is mainly used instead of directly using the concept of speed, but there are also the following requirements for the indoor air speed;

(1) The air velocity at the outlet of the air outlet should not be too large. Compared with a simple air-conditioned room, it requires faster speed attenuation and a greater spread angle.

(2) The air flow velocity (for example, the recirculation speed at the time of side feeding) that is blown over the horizontal plane should not be too large, so as not to blow up the surface particles to return to the air flow and cause re-contamination. This speed is generally not recommended to be as large as 0.2 m/s.

For the parallel-flow clean room “commonly referred to as the laminar clean room”, the speed of the cross-section is a very important indicator due to the fact that the piston is mainly used for air flow to exclude the dyeing. In the past, reference was made to the United States 20gB standard and 0.45 was used. m/s. But people have also learned that the amount of ventilation required for such a large speed is very large. In order to save energy, they are also seeking the feasibility of reducing the speed of wind.

In China, both the Air Cleantech Measures and the Cleanroom Design Code are

Vertical parallel flow (laminar flow) clean room ≥0.25m/s

Horizontal parallel flow (laminar flow) clean room ≥ 0.35 m/s

Noise control


Noise standards for clean laboratory construction are generally stricter than those for protection of health. The purpose is to ensure that operations are carried out normally and that necessary conversational contact and a safe and comfortable working environment are met. Therefore, the main indicator of noise in a clean room is.


1. The effect of trouble


Due to noise, people feel uneasy and have trouble emotions. They are generally divided into very quiet, very quiet, quiet, slightly noisy, relatively noisy and extremely noisy. Where the level of response is very noisy and extremely noisy, it is high anxiety, and the percentage of high number of troubles in the total number is high anxiety rate.


2. Impact on work efficiency


This mainly depends on the level of response in the three areas. These three aspects are: concentration, accuracy of action, and speed of work;


3. Interference with integrated communications