Standard Method for Measuring and Counting Particulate Contamination on Surfaces

SCOPE
1.1 This method covers the size distribution analysis of particulate contamination, 5 m or greater in size, either on, or washed from, the surface of small electron-device components. A maximum variation of two to one (33 % of the average of two runs) should be expected for replicate counts on the same sample.
Note 1--For satisfactory results on clean parts, it is recommended that all procedures involved in sample preparation be conducted under a dust shield.

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09-May-2000
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ASTM F24-00 - Standard Method for Measuring and Counting Particulate Contamination on Surfaces
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: F 24 – 00
Standard Method for
Measuring and Counting Particulate Contamination on
Surfaces
This standard is issued under the fixed designation F 24; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript
epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope filtration and then examined microscopically. Microscopical
analysis of the contaminant is conducted at two magnifications
1.1 This method covers the size distribution analysis of
using a gating measurement technique with oblique incident
particulate contamination, 5 μm or greater in size, either on, or
lighting. Particles are counted in three size ranges: >100 μm, 25
washed from, the surface of small electron-device components.
to 100 μm, 5 to 25 μm, and fibers. For low-contamination
A maximum variation of two to one (633 % of the average of
levels on irregularly shaped components, a procedure for
two runs) should be expected for replicate counts on the same
running a blank is described. The method required strict
sample.
adherence to the procedures for cleaning apparatus.
NOTE 1—For satisfactory results on clean parts, it is recommended that
all procedures involved in sample preparation be conducted under a dust
4. Apparatus
shield.
4.1 Microscope, with mechanical stage, approximately 45
and 1003. For 1003 magnification, the recommended objec-
2. Terminology
tive is 10 to 123 (but a minimum of 63) with a numerical
2.1 Definitions:
aperture of 0.15 minimum. The optimum equipment is a
2.1.1 particulate contaminant—a discrete quantity of matter
binocular microscope with a micrometer stage. A stereomicro-
that is either foreign to the surface on which it rests or may be
scope should not be used in this procedure.
washed from the surface on which it rests by the ultrasonic
4.2 Ocular Micrometer,B&L 31-16-10, or equivalent.
energy procedure herein described.
4.3 Stage Micrometer,B&L 31-16-99, or equivalent,
2.1.2 particle size—the maximum dimension of the particle.
having 0.1- to 0.01-mm calibration.
2.1.3 fibers—particles longer than 100 μm with a length to
4.4 Light Source—An external incandescent high-intensity,
width ratio of greater than 10:1.
6-V, 5-A source with transformer.
2.1.4 planar surface—a surface that does not move out of
4.5 Microscope Slides—Glass slides 50 by 75 mm.
the depth of field of the microscope when the area to be
4.6 Plastic Film —Wash with membrane-filtered isopropyl
observed is traversed under the highest magnification to be
alcohol.
used.
4.7 Solvent Filtering Dispenser.
4.8 Membrane Filter Holder, having 47-mm diameter and
3. Summary of Method
heat-resistant glass base.
3.1 The method comprises two procedures for preparing
4.9 Filter Flask,1L.
specimens for microscopical analysis: one for adhered particles
4.10 Membrane Filters, having 47-mm diameter, 0.45-μm
on planar surfaces and the second for particulate contamination
pore size, black, grid marked.
removed from irregular surfaces. A single optical analysis
4.11 Vacuum Source—Pump or aspirator (tap recom-
procedure is presented for particle enumeration in stated size
mended).
ranges. For planar surfaces, the component is mounted on a
4.12 Flat Forceps, with unserrated tips.
suitable flat support and mounted on the microscope stage. For
4.13 Plastic Petri Dishes.
irregular surface components, the contamination is removed by
subjecting the component to an ultrasonic cavitation field while
immersed in water containing a detergent. The contamination
is subsequently transferred to a membrane filter disk by Saran plastic film or equivalent has been found satisfactory for this purpose.
Millipore Type XX 66 02500, manufactured by the Millipore Filter Corp., or
equivalent, has been found satisfactory for this purpose.
Millipore XX 1004700 or equivalent has been found satisfactory for this
This method is under the jurisdiction of ASTM Committee E-21 on Space purpose.
Simulation and Applications of Space Technology and is the direct responsibility of Millipore Type HABG 04700 manufactured by the Millipore Filter Corp., or
Subcommittee E21.05 on Contamination. equivalent, has been found satisfactory for this purpose.
Current edition approved May 10, 2000. Published September 2000. Originally Millipore PD 10 04700 or equivalent has been found satisfactory for this
published as F 24 – 62 T. Discontinued January 1992 and reinstated as F 24 – 00. purpose.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F24–00
NOTE 2—Plastic petri dishes should not be reused for conducting these
7.2.5 Remove the extracted part from the beaker and rinse
tests.
thoroughly with membrane-filtered water allowing the water to
4.14 Ultrasonic Energy Cleaning Apparatus, having 2-L run into the beaker.
minimum capacity (see Appendix X1).
7.2.6 Transfer the fluid from the beaker into the funnel of
4.15 Beaker, 500-mL, chemical-resistant glass.
the filter holder. Rinse the beaker with 50 mL of filtered water,
4.16 Double-Faced Pressure-Sensitive Tape.
or solvent and add this rinse to the funnel.
7.2.7 Cover the funnel with a piece of clean aluminum foil
5. Reagents
or a cleaned 150-mm glass petri dish.
5.1 Isopropyl Alcohol, ACS reagent grade, membrane-
7.2.8 Apply a vacuum to the filter flask until the liquid has
filtered.
completely passed through the filter. Do not add additional
5.2 Nonionic Liquid Wetting Agent, membrane-filtered.
fluid to the funnel after the filter surface has become clear of
5.3 Water—Deionized or distilled water, membrane-filtered.
liquid as this will upset the particle distribution on the filter.
NOTE 3—Membrane-filtered reagents shall be stored in bottles pre-
7.2.9 Turn off the vacuum, remove the filter from the holder
cleaned as described in 7.2.1 or by use of Swinney hypodermic filters in
base with a forceps, and place the filter in a plastic petri dish
a Guth bottle. A procedure for control analysis of reagent cleanness is
with the cover ajar. Label the dish and allow the filter to dry for
described in Appendix X2.
at least 30 min.
6. Determination of Background Counts
NOTE 6—If the filter curls on the slide, apply a thin coat of silicone
6.1 Prepare a blank by following steps 7.2.1-7.2.10, without
grease to the slide under the filter. Alternatively, the filter dish may be
introduction of the part, for the purpose of determining sandwiched between ultrasonically cleaned glass slides.
background counts (which are to be subtracted from the final
7.2.10 When ready for the microscopical analysis, transfer
counts when parts are used). If excessively high background
the filter with a forceps to the surface of a 50- by 75-mm glass
counts are obtained, cleaning procedures and handling should
microscope slide.
be reexamined before proceeding.
NOTE 7—Storage of filters in a glass petri dish permits forced drying at
7. Preparation of Test Specimens
temperatures of 60 to 70°C and allows more rapid sample handling.
7.1 For Planar Surfaces:
7.
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