The air cleanliness testing of cleanroom

The air cleanliness testing of cleanroom

The air cleanliness of cleanroom, should undertake the following tests:

A  Empty state & static testing
Empty state test: under the conditions of cleanroom has been completed & the purify air conditioning system has been in a state of normal operation, to do the test without process equipment and production personnel indoor.
Static test: under the conditions of cleanroom purify air conditioning system is in normal operation condition and process equipment has been installed, to do the test without production personnel indoor.

B  To do the dynamic testing cleanroom under the normal production.
Clean room air volume, wind speed, positive pressure, temperature, humidity, noise detection, can according to the relevant provisions of the general gm & air conditioning to execute.

Empty state, static testing
A   the preparation before the test
1. Response to the clean room clean air conditioning system to make a thorough clean.

2、Using light scattering particle counter to do the leak detection test for HEPA filter. First determine the dust grain number of upper side of the HEPA air filter static pressure box (or air hose) particle size ≥0.5um should be ≥30000 / l. If not enough, smoke can be introduced, and then began to leak detection. Put the particle counter (or leak detection devices) about 2~3cm to the sampling port of the HEPA filter, can move at a speed of 2 ~ 4 cm/sec, to scan the whole section head at the glue and mounting frame. When the dust particles of particle counter?≥0.5um over 3 grain/min.l (or the penetration rate ＞0.01‰)，that it has obvious leakage, must be prevented leak.

B  Test content
1. The total air supply volume, total return air volume, fresh air volume, exhaust air volume, etc.
2. Clean room pressure value.
3. The section air velocity and air flow of laminar flow cleanroom.
4. The cleanliness of clean work area.
5. Indoor temperature, humidity and the adjust test of control capabilities.
6. The indoor noise of cleanroom.

C  The test method for air cleanliness of the clean work area for the particle size ≥0.5um, it’s better to adopt a light scattering particle counting method. For the particle size ≥0.5um, it can also be used membrane microscope counting method.

Light scattering particle counting method
1、Light scattering particle counter sample volume for 100 rank: each time the sample volume ≥1 liter.
For 1,000~10,000 rank: each time the sample volume ≥0.3 liter.
For 100,000 rank: each time the sample volume ≥0.1 liter.
For the 100 rank cleanroom, it should be used to test by the large flow particle counter. If the conditions are not available, it can be used for each sample not less than 1 liter of particle counter.

2、Sampling Notes：
(1) The sampling tube must be clean, junction is strictly prohibited leakage.
(2) The length of sampling tube, should be based on allowable length of the instrument. If not has the specified, should be less than 1.5 meters.
(3) The sampling nozzle velocity, should close to the average wind speed of cleanroom section. The tester should at the downwind of sampling port.
(4) Sample order should be in accordance with the dust concentration from low to high.

3、Monitoring point arrangement
(1) Testing should be proceed in the clean work area. When the production process without special requirements, sampling height appropriate for one meter from the ground.
(2) The total measuring point of laminar flow clean room not less than 20 points, each measuring point distance is from 0.5um to 2.0um. The number of dust particle size ≥ 0.5 microns allows more than one point. The measuring points of horizontal laminar flow clean room only arranged in the first clean workspace.
(3) Turbulence cleanroom according to clean area, if ≤ 50 square meters are arranged five measuring points (attached map 2). Each additional 20~50 square meters, add 3~5 measuring points.

4、Data processing
(1) Data processing of each measuring point should be three consecutive sampling under conditions of stable operation of test equipment, take the average value, is the point at which the measured value.

(2) For the number of dust particles ≥ 0.5um: laminar flow cleanroom to take each maximum measurement point, turbulence cleanroom averaged each measuring point.

D  Positive pressure measuring should adopt the micromanometers which the accuracy up to 0.01 mm water column.

Dynamic Testing. The operating position in the clean workspace choose a representative measuring point on the airflow wind direction, the test method is the same with empty state & static testing.