# ASTM F24-09 (Reapproved 2015)

Designation: F24 − 09 (Reapproved 2015)Standard Test Method forMeasuring and Counting Particulate Contamination onSurfaces1This standard is issued under the fixed designation F24; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon (´) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the size distribution analysis ofparticulate contamination, 5 µm or greater in size, either on, orwashed from, the surface of small electron-device components.A maximum variation of two to one (633 % of the average oftwo runs) should be expected for replicate counts on the samesample.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.2. Terminology2.1 Definitions:2.1.1 particulate contaminant—a discrete quantity of matterthat is either foreign to the surface on which it rests or may bewashed from the surface on which it rests by the ultrasonicenergy procedure herein described.2.1.2 particle size—the maximum dimension of the particle.2.1.3 fiber—a particle longer than 100 µm and with a lengthto width ratio of greater than 10:1.2.1.4 planar surface—a surface that does not move out ofthe depth of field of the microscope when the area to beobserved is traversed under the highest magnification to beused.3. Summary of Method3.1 This test method comprises two procedures for prepar-ing specimens for microscopical analysis: one for adheredparticles on planar surfaces and the second for particulatecontamination removed from irregular surfaces.3.2 A single optical analysis procedure is presented forparticle enumeration in stated size ranges.3.3 For planar surfaces, the component is mounted on asuitable flat support and mounted on the microscope stage. Forirregular surface components, the contamination is removed bysubjecting the component to an ultrasonic cavitation field whileimmersed in water containing a detergent.3.4 The contamination is subsequently transferred to amembrane filter disk by filtration and then examined micro-scopically.3.5 Microscopical analysis of the contaminant is conductedat two magnifications using a gating measurement techniquewith oblique incident lighting.3.6 Particles are counted in three size ranges: 100 µm, 25to 100 µm, 5 to 25 µm, and fibers.3.7 For low-contamination levels on irregularly shapedcomponents, a procedure for running a blank is described.3.8 The method requires strict adherence to the proceduresfor cleaning apparatus.4. Apparatus4.1 Microscope, with mechanical stage, approximately 45and 100×. For 100× magnification, the recommended objectiveis 10 to 12× (but a minimum of 6×) with a numerical apertureof 0.15 minimum. The optimum equipment is a binocularmicroscope with a micrometer stage. A stereomicroscopeshould not be used in this procedure.4.2 Ocular Micrometer, B particulate contamination;size distribution analysis; surfacesAPPENDIXES(Nonmandatory Information)(Informative)X1. SELECTION OF ULTRASONIC EQUIPMENTX1.1 To provide uniform and reliable ultrasonic energy, thefollowing factors should be considered in selecting the equip-ment:X1.1.1 The type of transducer and method of bondingshould be selected so that frequency, inductance, and couplingcoefficient are unchanged by heat, vibration, and age.X1.1.2 The type of transducer and frequency should beselected to minimize focusing of energy in specific areas.X1.1.3 The power of the transducer should be chosen toprevent standing waves (which do not allow vaporous cavita-tion) and to prevent physical damage and cavitation erosion.X2. METHOD OF COUNTING AND MEASURING PARTICLESX2.1 In obtaining the number of particles of a certain sizerange, the number of particles on a representative number ofgrid squares on the membrane filter paper is counted. From thiscount, the total number of particles, which would be presentstatistically on the total filtered area of 100 imprinted gridsquares, is calculated.X2.2 If the total number of particles of a certain size rangeis estimated to be between 1 and 50, count the number ofparticles on all 100 grid squares.X2.3 If the total number of particles of a certain size rangeis estimated to be between 50 and 1000, count the number ofparticles in 20 randomly chosen grid squares and multiply thisnumber by 5 to obtain the statistical total particle count.X2.4 If the total number of particles of a certain size rangeis estimated to be between 1000 and 5000, count the number ofparticles on 10 randomly chosen grid squares and multiply thisnumber by 10 to obtain the statistical total particle count.X2.5 If the estimated total number of particles of a givensize range exceeds 5000, particles are counted in standardfractions of grid areas (Fig. X2.1).X2.6 Count the particles within at least 10 of these frac-tional areas.F24 − 09 (2015)3X2.7 Multiply the average count per fractional area by theratio of the effective filtration area, to the area counted.X2.8 Select fractional area so that there will be no morethan about 50 particles of a size range.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or service@astm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http://www.copyright.com/NOTE 1—With membrane filter on stage, movement of the stage makesparticles appear to pass the divisions on the measuring eyepiece.FIG. X2.1 Alternative Unit AreasF24 − 09 (2015)4