Electronic Industry Cleanroom Testing Key Points

The key testing parameters for clean areas in electronic industry cleanroom include cleanliness, cross-sectional airflow velocity and air change rate, temperature and relative humidity, noise, and illumination. The testing sequence is as follows: cross-sectional airflow velocity and air change rate > cleanliness > noise and temperature/humidity, while illumination testing can be interspersed during any of the other testing processes. The reasons are as follows:

(1) Cross-sectional airflow velocity or air change rate is a crucial guarantee for the delivery of clean air into the cleanroom. Only when the cross-sectional airflow velocity or air change rate meets the requirements is it meaningful to discuss the cleanliness and other key parameters of the cleanroom.

(2) Cleanliness is the core parameter expressing the air supply effect, cleanliness, and uniformity of the clean area, and is the most direct reflection of the air supply effect of the cleanroom air conditioning system.

(3) The air supply, return air, or exhaust air velocity and the vibration level of the air ducts are important factors affecting indoor noise; the supply air temperature and humidity affect the indoor temperature and relative humidity.

(4) Cleanroom illumination is a parameter independent of the performance of the cleanroom air conditioning system; therefore, illumination testing can be interspersed during the testing of the above key parameters.

For cleanliness testing, an optical particle counter with a sampling volume of not less than 1 L/min should be used for particle concentration sampling. The number of testing points should be determined according to the square root of the area of ​​the room being tested, and the testing points should be located at the working area height (usually 750-900 mm above the ground) and at a distance of no less than 300 mm from any equipment or wall; the testing points must be evenly distributed and cover all areas.

For cross-sectional airflow velocity and air change rate testing, a precision anemometer is usually used, and the minimum scale or reading of the instrument should not exceed 0.02 m/s. For unidirectional flow cleanroom, the cross-sectional airflow velocity should be measured on an unobstructed surface 0.8 m above the ground; if there is an obstruction, the measurement should be taken 0.25 m above the obstruction. The distance between measurement points on the cross-section can be 0.3-0.5 m, and the number of measurement points should generally not be less than 20.

For cleanroom with HVAC air conditioning and purification systems, temperature and humidity measurements should only be taken after the system has been running continuously for more than 12 hours. Furthermore, after indoor temperature and humidity measurements are completed, outdoor temperature and humidity should also be measured. Generally, no special requirements are placed on the temperature and humidity measuring instruments. Temperature and humidity measurement points are typically required to be at a height of 0.8 m above the ground and more than 0.5 m from the outer wall surface.

For illuminance and noise measurements, a portable illuminance meter is typically used for illuminance testing, with a minimum scale of no greater than 21 lux. Noise is generally only measured at the A-weighted sound level, and the minimum scale of the sound level meter should not be less than 0.2 dB(A). Illuminance measurement points should be located at the working surface height, 0.85 m above the ground, with one point for every 25m². When the room area is less than 30m², the measurement points should be 0.5 m from the wall; when the area exceeds 30 m², they should be 1 m from the wall. Noise measurement points should be 1.1 to 1.5 m above the ground, and to avoid interference from wall echoes, they should be more than 3 m from the wall. Measurement points should be evenly distributed, with one measurement point for every 100m².