Temperature and humidity control of clean space in purification project is mainly determined according to technological requirements, but under the condition of meeting technological requirements, people's comfort should be taken into account. With the improvement of air cleanliness requirement, the requirement of temperature and humidity is becoming more and more stringent.

Specific process requirements for temperature will be listed later, but as a general principle, because the processing accuracy is more and more fine, so the requirements for the range of temperature fluctuation are becoming smaller and smaller. For example, in the lithographic exposure process of large scale integrated circuit production, the difference of thermal expansion coefficient between glass and silicon wafer as mask material is becoming smaller and smaller.

Silicon wafers with a diameter of 100 um cause linear expansion of 0.24 um when the temperature rises by 1 degree. Therefore, it is necessary to have a constant temperature of (+0.1 degree) and the humidity value is generally low, because the products will be polluted after sweating, especially in semiconductor workshop for fear of sodium. The temperature of this workshop should not exceed 25 degrees, and the problem caused by excessive humidity is even more serious. Many. When the relative humidity exceeds 55%, condensation will occur on the cooling water pipe wall. If it occurs in precision devices or circuits, it will cause various accidents. It is easy to rust when the relative humidity is 50%.
In addition, when the humidity is too high, the dust adsorbed on the surface of silicon wafer will be chemically adsorbed by water molecules in the air, which is difficult to remove. The higher the relative humidity is, the more difficult it is to remove the adhesion. However, when the relative humidity is below 30%, the particles are easily adsorbed on the surface due to the action of electrostatic force. At the same time, a large number of semiconductor devices are prone to breakdown. The optimum humidity range for silicon wafer production is 35-45%.
For most clean spaces, in order to prevent the invasion of external pollution, it is necessary to keep the internal pressure (static pressure) higher than the external pressure (static pressure). Pressure differential maintenance should generally comply with the following principles:
1. The pressure of clean space is higher than that of non-clean space.
2. The pressure of space with high cleanliness level is higher than that of adjacent space with low cleanliness level.
The maintenance of pressure difference depends on fresh air volume, which can compensate for the air leakage from the gap under this pressure difference. Therefore, the physical meaning of pressure difference is the resistance of air leakage (or infiltration) through various cracks in the clean room.
Air velocity regulation in clean room
The airflow velocity discussed here refers to the airflow velocity in the clean room. The airflow velocity in other clean spaces is explained when discussing specific equipment.
For turbulent clean rooms, because the main function of reducing indoor pollution is the dilution of air, the concept of ventilation frequency is mainly used instead of the concept of speed. However, there are also the following requirements for indoor air velocity.
(1) The air velocity at the outlet of the air supply outlet should not be too high. Compared with a single air-conditioned room, the speed attenuation is required to be faster and the diffusion angle is larger.
(2) The velocity of air flowing through the horizontal plane (e.g. the reflux velocity when side feeding) should not be too high to prevent the surface particles from returning to the air flow and causing re-pollution, which is generally not suitable to dry 0.2m/s.
For the parallel flow clean room, which is customarily called laminar flow clean room, the speed on the cross section is a very important index because it mainly depends on the "piston extrusion effect" of air flow to exclude dyeing. In the past, reference was made to the 20gB standard of the United States and 0.45m/s was adopted. However, people also know that the ventilation required for such a large speed is extremely large. In order to save energy, they are also exploring the feasibility of reducing the wind speed.
In our country, the "Technical Measures for Air Cleaning" and "Design Code for Clean Workshops" both stipulate that the vertical parallel flow (laminar flow) clean room (> 0.25m/s) horizontal parallel flow (laminar flow) clean room (> 0.35m/s) noise control. The noise standard of clean room is generally stricter than the standard of health protection. The purpose is to ensure normal operation. To satisfy the necessary communication and safe and comfortable working environment.
Indicators for Measuring Clean Room Noise
1. The Effect of Trouble
Noise makes people feel uneasy and produces annoyance. Generally, it can be divided into seven levels: extremely quiet, very quiet, relatively quiet, slightly noisy, relatively noisy and extremely noisy. Where the level of reaction belongs to those who are very noisy and very noisy, it is a high rate of worry, and the percentage of the number of people with high level of worry in the total number is a high rate of worry.
2. The influence on work efficiency mainly depends on three aspects: concentration, accuracy and speed of work.
3. The interference to the integrated communication is mainly divided into: clear or satisfied, slightly difficult and difficult. It is impossible to evaluate the above three indicators with A sound level. In the 1950s, it was proposed that a spectral curve should be used as an evaluation criterion, that is, the sound pressure level of the central frequency of each frequency band should not exceed the curve.
Later, it was found that brush A level is more suitable for measuring the speech interference and annoyance of noise and noise, and can replace the sound pressure level of frequency doubling band as an index of evaluation criteria.
Firstly, the lighting mode of windowless clean room is explained.
(1) General lighting refers to the lighting set up to illuminate the whole illuminated area without considering the special local needs.
(2) Local illumination refers to the illumination set up to increase the illumination of a designated place, such as a work point. But in indoor lighting, local lighting is not used alone.
(3) Mixed illumination refers to the illumination on the working face which is composed of general illumination and local illumination. The illumination of general illumination should account for 10%-15% of the total illumination according to the Code for Design of Clean Workshop, but not less than 150 LX dry. The light flux received per unit of illuminated area is the illumination unit Lux (LX).
The strength requirement of cleanrooms abroad is very high. For example, in the United States, the requirements of several standards for cleanrooms are that artificial light 300lx has better effect. When the workpiece is more fine, 500X is also allowed. For places requiring red light illumination, such as photolithography workshop in electronic industry, the illumination is generally (25-501x). Higher illumination can be allowed when natural light is used, which is beneficial to work. Therefore, it may be promising to use both artificial light and natural light in future clean room lighting, which is also a kind of energy saving. Trends.
Antistatic
Accidents caused by static electricity often occur in clean rooms, so how to prevent static electricity in clean rooms has become an important aspect in evaluating their quality.
The so-called static electricity is due to friction and other reasons, which destroys the uniform neutral state of positive (+) negative < 1) charges in the object, and causes excess charges. The object is charged. Because these charges are usually not flowing, they are called static electricity.
Accidents caused by static electricity in clean rooms include the following aspects.
1. Electrostatic shock caused by electrostatic electricity can cause people's insecurity and fear, and can cause secondary injury (for example, people fall because of electrostatic shock, and people fall because of injury);
2. The discharge current caused by electrostatic discharge can lead to damage and misoperation such as semiconductor devices. For example, 50 P-MOS circuits are placed in plastic bags. After shaking several times, 39 of them break down seriously with non-gate electrodes. The failure rate is 78%, which is because semiconductor devices are very sensitive to electrostatic discharge.
3. Electromagnetic waves generated by electrostatic discharge can lead to noise and misoperation of electronic instruments and devices.
4. Electrostatic discharge (ESD) can cause photosensitive damage such as photographic limbs.
5. The mechanical phenomena of static electricity can cause the screen hole to be blocked by dust, the yarn to be chaotic, the printing material to be uneven and the product to be polluted.
The main causes of electrostatic accidents lie in the generation and accumulation of static electricity. The flow of air, friction between air and pipes, air outlets and filters, friction between human body and clothes, friction between clothes, technological grinding, spraying, jet, washing, stirring, bonding and peeling operations, all of which may produce static electricity. In general, the less conductive the non-conductor (insulator) is, the easier it is to be charged because it is not easy to flow after the charge is generated.
The electrostatic problem is particularly serious in clean rooms, because not only have the aforementioned various technological factors of generating static electricity in clean rooms, but also because many materials in clean rooms, such as plastic floor, wall, nylon, dacron and other work clothes, have very high resistivity, they are very easy to generate static electricity and collect static electricity, so they are clean. These materials were widely used before the electrostatic hazards in the room were ignored.
As a professional project design, system engineering construction, supporting product sales purification engineering enterprise, Edward Purification has professional secondary qualification of purification engineering, strong strength, rich experience, strict to every detail of purification engineering, to ensure the quality of purification operation room, is a trustworthy purification manufacturer for customers.
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