1、Designation: E 2090 06Standard Test Method forSize-Differentiated Counting of Particles and FibersReleased from Cleanroom Wipers Using Optical andScanning Electron Microscopy1This standard is issued under the fixed designation E 2090; the number immediately following the designation indicates the ye
2、ar oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONTechniques for determining the number of particles an
3、d fibers that can potentially be released fromwiping materials consist of two steps. The first step is to separate the particles and fibers from thewiper and capture them in a suitable medium for counting, and the second step is to quantify thenumber and size of the released particles and fibers.The
4、 procedure used in this test method to separate particles and fibers from the body of the wiperis designed to simulate conditions that the wiper would experience during typical use. Therefore, thewiper is immersed in a standard low-surface-tension cleaning liquid (such as a surfactant/watersolution
5、or isopropyl alcohol/water solution) and then subjected to mechanical agitation in that liquid.The application of moderate mechanical energy to a wiper immersed in a cleaning solution is effectivein removing most of the particles that would be released from a wiper during typical cleanroomwiping. Th
6、is test method assumes the wiper is not damaged by chemical or mechanical activity duringthe test.Once the particles have been released from the wiper into the cleaning solution, they can becollected and counted. The collection of the particles is accomplished through filtration of theparticle-laden
7、 test liquid onto a microporous membrane filter. The filter is then examined using bothoptical and scanning electron microscopy where particles are analyzed and counted. Microscopy waschosen over automated liquid particle counters for greater accuracy in counting as well as formorphological identifi
8、cation of the particles.The comprehensive nature of this technique involves the use of a scanning electron microscope(SEM) to count particles distributed on a microporous membrane filter and a stereo-binocular opticalmicroscope to count large fibers. Computer-based image analysis and counting is use
9、d for fields wherethe particle density is too great to be accurately determined by manual counting.Instead of sampling aliquots, the entire amount of liquid containing the particles and fibers insuspension is filtered through a microporous membrane filter. The filtering technique is crucial to thepr
10、ocedure for counting particles. Because only a small portion of the filter will actually be counted,the filtration must produce a random and uniform distribution of particles on the filter. After filtration,the filter is mounted on an SEM stub and examined using the optical microscope for uniformity
11、 ofdistribution. Large fibers are also counted during this step. Once uniformity is determined and largefibers are counted, the sample stub is transferred to the SEM and examined for particles.Astatisticallyvalid procedure for counting is described in this test method. The accuracy and precision of
12、theresultant count can likewise be measured.This test method offers the advantage of a single sample preparation for the counting of bothparticles and fibers. It also adds the capability of computerized image analysis, which providesaccurate recognition and sizing of particles and fibers. Using diff
13、erent magnifications, particles from0.5 to 1000 m or larger can be counted and classified by size. This procedure categorizes three classesof particles and fibers: small particles between 0.5 and 5 m; large particles greater than 5 m butsmaller than 100 m; and large particles and fibers equal to or
14、greater than 100 m. The technique asdescribed in this test method uses optical microscopy to count large particles and fibers greater than100 m and SEM to count the other two classes of particles. However, optical microscopy can beemployed as a substitute for SEM to count the large particles between
15、 5 and 100 m2.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.1. Scope1.1 This test method covers testing all wipers used incleanrooms and other controlled environments for characteris-tics related to particulate cleanliness.1.2 This
16、 test method includes the use of computer-basedimage analysis and counting hardware and software for thecounting of densely particle-laden filters (see 7.7-7.9). Whilethe use of this equipment is not absolutely necessary, it isstrongly recommended to enhance the accuracy, speed, andconsistency of co
17、unting.1.3 The values stated in SI units are to be regarded as thestandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determin
18、e the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D 1193 Specification for Reagent WaterF25 Test Method for Sizing and Counting Airborne Par-ticulate Contamination in Cleanrooms and Other Dust-Controlled AreasF 312 Test Methods for Microscopical S
19、izing and CountingParticles from Aerospace Fluids on Membrane Filters2.2 Other Documents:ISO 14644-1 Cleanrooms and Associated Controlled Envi-ronments Classification of Air Cleanliness4ISO 14644-2 Cleanrooms and Associated Controlled Envi-ronments Part 2: Specifications for testing and monitor-ing
20、to prove continued compliance with ISO 14644-14Fed. Std. 209E Airborne Particulate Cleanliness Classes inCleanrooms and Clean Zones53. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 automatic counting, ncounting and sizing per-formed using computerized image analysis software.3.
21、1.2 cleanroom wiper, na piece of absorbent knit, wo-ven, nonwoven, or foam material used in a cleanroom forwiping, spill pickup, or applying a liquid to a surface.3.1.2.1 DiscussionCharacteristically, these wipers pos-sess very small amounts of particulate and ionic contaminantsand are primarily use
22、d in cleanrooms in the semiconductor,data storage, pharmaceutical, biotechnology, aerospace, andautomotive industries.3.1.3 effective filter area, nthe area of the membranewhich entraps the particles to be counted.3.1.4 fiber, na particle having a length to diameter ratio of10 or greater.3.1.5 illum
23、inance, nluminous flux incident per unit ofarea.3.1.6 particle, na unit of matter with observable length,width, and thickness.3.1.7 particle size, nthe size of a particle as defined by itslongest dimension on any axis.4. Summary of Test Method4.1 Summary of Counting MethodsSee the following:Counting
24、 Technique Particle Size Range100 m 5100 m 0.55 mStereobinocular optical microscope 203manualANABScanning electron microscope NA 2003 auto 30003 manualor automaticBASee Footnote 2.BNA = not applicable.5. Significance and Use5.1 This test method provides for accurate and reproducibleenumeration of pa
25、rticles and fibers released from a wiperimmersed in a cleaning solution with moderate mechanicalstress applied. When performed correctly, this counting testmethod is sensitive enough to quantify very low levels of totalparticle and fiber burden. The results are accurate and notinfluenced by artifact
26、 or particle size limitations. A furtheradvantage to this technique is that it allows for morphologicalas well as X-ray analysis of individual particles.6. Apparatus6.1 Scanning Electron Microscope, with high-quality imag-ing and computerized stage/specimen mapping capability.6.2 Stereo-Binocular Op
27、tical Microscope, with at least403-magnification capability equipped with a two-arm,adjustable-angle variable-intensity light source and a specimenholding plate.6.3 Orbital Shaker, that provides 20-mm (34-in.) diametercircular motion in a horizontal plane at 150 r/min.6.4 Microanalytical Stainless S
28、teel Screen-Supported Mem-brane Filtration Apparatus, with stainless steel funnel, TFE-fluorocarbon gasket and spring clamp.6.5 Vacuum Pump, capable of providing a pressure of 6.5kPa (65 mb) (49 torr) or lower.6.6 Cold Sputter/Etch Unit, with gold or gold/palladiumfoils.6.7 Video Camera (3-CCD prefe
29、rable), that can be attachedto the stereo-binocular microscope and a monitor to providevideo microscopy capability.6.8 Personal Computer (486-Type Processor or Better) andMonitor.1This test method is under the jurisdiction of ASTM Committee E21 on SpaceSimulation and Applications of Space Technology
30、 and is the direct responsibility ofSubcommittee E21.05 on Contamination.Current edition approved Nov. 1, 2006. Published December 2006. Originallyapproved in 2000. Last previous edition approved in 2000 as E 2090 - 00.2The counting of particles 5 to 100 m by optical microscopy is not describedin th
31、is test method. However, procedures for counting particles in this size range aredescribed in the Test Methods F25and F 312.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, r
32、efer to the standards Document Summary page onthe ASTM website.4Available from American National Standards Institute, 11 W. 42nd St., 13thFloor, New York, NY 10036.5Cancelled Nov. 29, 2001 and replaced with ISO 14644-1 and ISO 14644-2,FED-STD-209E may be used by mutual agreement between buyer and se
33、ller.Available from US Government Printing Office, Superintendent of Documents, 732N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401.E20900626.9 Frame-Grabbing Hardware and Image Analysis Soft-ware, compatible with the personal computer.66.10 Hand-Operated Tally Counter.6.11 Stage Micrometer,
34、 with 0.1- and 0.01-mm subdivi-sions.6.12 Horizontal, Unidirectional Flow Workstation, withISO Class 5 (Fed. Std. 209 Class 100) or cleaner air.7. Materials7.1 Deionized Water, in accordance with SpecificationD 1193, Type III, 4.0 3 106(V-cm)1or better.7.2 Cleanroom Gloves (for example, unpowdered l
35、atexgloves).7.3 Fine-Point, Duckbill Tweezers.7.4 Forceps, two pairs, with flat gripping surface tips.7.5 Glass Beakers, 1.5 L, cleaned in accordance with 10.2.1.7.6 Polyethylene Photographic Tray, approximately 250 by340 by 45 mm cleaned in accordance with 10.2.1.7.7 Polycarbonate Membrane Filters
36、(typically 0.1- to0.4-m pore size), white, and 25-mm diameter.7.8 Petri Slide,47mm.7.9 SEM Aluminum Specimen Stubs, typically 32-mm diam-eter by 10-mm height.7.10 Polystyrene Latex Microspheres (sizes 0.5 and 5 m)for use in calibration (see Section 9).7.11 Carbon Paint, for SEM stub preparation.7.12
37、 Low-Surface-Tension Cleaning LiquidAny 8- to 10-mole ethoxylated-octyl- or nonyl-phenol-type surfactant7pre-pared as a 0.1 % stock solution in deionized water. Thissolution will facilitate the release of both nonpolar and polarcontaminants and can serve as a general test standard acrossindustries.
38、However, this test method is not limited to a specificcleaning solution and only requires that the cleaning liquidused be relatively free of particles and fibers. It is recom-mended that the cleaning liquid most relevant to the productend use be considered for this test method.8. Preparation of Appa
39、ratus8.1 Setting Up Stereo-Binocular Optical MicroscopeSeeSection 10.8.2 Fiber Counting by Optical MicroscopySee Section10.8.3 Setting Up Scanning Electron Microscope (SEM)SeeSection 10.8.4 Particle Counting by SEMSee Section 10.9. Calibration and Standardization9.1 For the fiber counting by optical
40、 microscopy, the sizecalibration at 203 magnification can be done by comparing thefiber sizes, as visualized in the video monitor, with the rulingson the stage micrometer (with 0.1- and 0.01-mm subdivisions).For the equipment described above, a linear dimension of 8mm in the video screen equaled 100
41、 m. The conversionfactors are equipment-dependent and users of this test methodshall establish the relation between screen size and object size.9.2 In the SEM study, to determine the values of the startand the end areas for the computer-assisted automatic particlecounting, it is necessary to perform
42、 the size calibration studyby experimenting with standard-sized particles such as poly-styrene microspheres or actual particles of known dimensionswhich can be ascertained by using the micrometre bar mea-surement tool available on most SEMs.9.3 To prepare a stub with 0.5- and 5-m spheres, add 10 Lof
43、 each of the 0.5- and 5-m sphere suspensions to a beakercontaining 500 mL of deionized water.9.4 Filter the solution using a new membrane filter.9.5 Prepare the SEM stub. Save the stub in a clean containeras a standard size reference for the automatic particle countingat 200 and at 30003.9.6 For the
44、 manual procedure at 30003, avoid countingparticles having approximate linear lengths of 25 mm and up,as those will have sizes larger than 5 m as determined frommeasurements done against the micrometre bars at variousmagnifications in the SEM.10. Procedure10.1 The procedure consists of two parts: pr
45、eparing thesample and counting the fibers and particles. Fibers andparticles greater than 100 m are counted using an opticalmicroscope at 203 magnification; large (between 5 and 100m) and small (between 0.5 and 5 m) particles are countedusing an SEM at 200 and 30003 magnifications respectively.Both
46、manual and computer-aided automatic counting methodsare used in this procedure.10.1.1 Sample PreparationSample preparation consists oftwo steps:10.1.1.1 Preparation of a background filter stub and10.1.1.2 Preparation of the sample filter stub containingparticles released from a cleanroom wiper.10.2
47、Preparation of a Background Filter StubTo measurethe background level of particles from the glassware, polyeth-ylene tray, and filtration system, it is necessary to prepare anexperimental blank.10.2.1 The cleaning of the photographic tray, glassware, andthe filtration apparatus should be accomplishe
48、d in the follow-ing manner:10.2.1.1 Clean the photographic tray thoroughly by rinsingthe inner surface at least five times with deionized water.10.2.1.2 Ultrasonically clean the glassware, storage contain-ers, and filtration assembly then thoroughly rinse using deion-ized water.10.2.1.3 Allow all co
49、ntainers and assemblies to drain dry inthe unidirectional flow workstation.6“Image-Pro Plus,” Version 3.0, available from Media Cybernetics, has beenfound to be satisfactory for this test method.The sole source of supply of the apparatus known to the committee at this timeis Media Cybernetics. If you are aware of alternative suppliers, please provide thisinformation to ASTM International Headquarters. Your comments will receivecareful consideration at a meeting of the responsible technical committee,1whichyou may attend.7Tritont X-100 manufa
