Liquid Particle Count

What is LPC

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.

Scope

The test method covers the size distribution and quantitative analysis of particulate contamination readily releasable from the surface.

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 apparatus.

Brief Procedure

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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