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.
