The clean-room workshop project can be divided into 100, 1000, 10000 and 100000 according to different cleanliness. The cleanliness of semiconductor electronic cleaning workshop is required to be calculated according to the number of 0.5 micron dust particles contained in each cubic meter of air, which is generally above 100000 level standard. In the project of semiconductor electronic dust-free room, filters are needed to control the diffusion of small particle size dust. Generally speaking, the lower the wind speed in the operation of the dust-free workshop, the better the use effect of the filter.
In the clean-room workshop project, the lower the wind speed, the more obvious the diffusion effect of small particle size dust. This is mainly because the lower the wind speed in the clean workshop, the longer the retention time of air flow in the filter material, the more obvious the impact of dust on surrounding obstacles, and the higher the filtration efficiency. In most cases, if the high-efficiency filter is used in the dust-free workshop project, once the wind speed is reduced by half, the dust transmittance will be reduced by nearly one order of magnitude. If the wind speed is doubled, the transmittance will be increased by one order of magnitude. In the diffusion of small particle size dust, if the wind speed is high, the resistance will be large. If the service life of the filter is based on the final resistance, the service life of the filter will be short if the wind speed is high.
In the semiconductor electronic clean-room workshop project, the diffusion effect is similar to that of small particle size dust. If the filter material is electrostatic, the longer the dust stays in the filter material, the greater the possibility of being adsorbed by the material. When the wind speed of semiconductor electronic cleaning workshop changes, the filtering effect of electrostatic materials will be significantly changed. Therefore, in the engineering design of dust-free room, if there is static electricity on the materials, the air volume passing through each filter should be reduced as much as possible in the design of air conditioning system. For large particle dust dominated by inertia mechanism, according to the traditional theory, after the wind speed is reduced, the probability of collision between dust and fiber will be reduced, and the filtration efficiency will be reduced. However, in practice, this effect is not obvious, because the wind speed is small, the resilience of fiber to dust is also small, and the dust is easier to stick.