Liquid Particle Count
Liquid Particle Count is a consistent analytical method. It is
to determine the cleanliness by measuring and counting easily
releasable particulate contamination on surfaces of disk drive
parts in a wetted state under minimal stress conditions.
The test method covers the size distribution and quantitative
analysis of particulate contamination readily releasable from
A maximum variation of ±33% for three runs should be expected
from replicate counts on three specimens from the same sample.
All procedures involved in the sample preparation should be conducted
under a certified class 100 laminar flow hood.
This test is applicable to precision cleaned and cleanroom packaged
parts only. Gross clean parts could potentially overload the sensor
and contaminate the system.
Summary of Method
Contaminant is removed by immersing the part(s) in DI water which
may contain a surfactant.
The extracted contamination is subsequently sampled and analyzed
by a liquid particle count system.
The total accumulated or differential number of particles in the
extract at different particle sizes are counted.
A blank is also analyzed.
The method requires strict adherence to the procedures for cleaning
Determine the surface area of the part from the engineering drawing.
Rinse the LPC equipment with membrane-filtered deionized water.
Fill a beaker with certain amount of the filtered deionized water.
Check the cleanliness of the equipment.
Add sufficient detergent solution (e.g. Triton X-100) to make
a rinse solution. Again, check cleanliness of the rinse solution.
Extract the parts in rise solution.
Determine the accumulated or differential particle count for particles
according to the automatic LPC manufacture's instructions.
Repeat steps above for the duplicate and triplicate.
Purge the system with membrane-filtered deionized water and ensure
sensor cell is filled with clean deionized water
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