Unknown INTERNATIONAL STANDARD INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATION MEWYHAPOAHAR OPrAHM3AuklR I IO CTAH~APTM3A~klM Metallic coatings Measurement[.]
INTERNATIONAL STANDARD IS0 9220 First edition 1988-10-01 INTERNATIONAL ORGANIZATION ORGANISATION INTERNATIONALE MEWYHAPOAHAR OPrAHM3AuklR FOR STANDARDIZATION DE NORMALISATION I-IO CTAH~APTM3A~klM of coating Metallic coatings - Measurement method thickness - Scanning electron microscope Rev6tements m&alliques microscope klectronique - Mesurage B balayage de l’kpaisseur de rev&tement - M&hode au Reference number IS0 9220 : 1988 (E) `,,,`-`-`,,`,,`,`,,` - Copyright International Organization for Standardization Provided by IHS under license with ISO No reproduction or networking permitted without license from IHS Not for Resale IS0 9220: 1988 (E) Foreword IS0 (the International national standards Standards Organization bodies (IS0 is normally `,,,`-`-`,,`,,`,`,,` - body interested for Standardization) member bodies) carried out through IS0 is a worldwide technical in a subject for which a technical federation The work of preparing committees committee of International Each member has been established has the right to be represented on that committee International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work IS0 collaborates closely with the International matters of electrotechnical Draft International Electrotechnical Standards adopted by the technical the member bodies for approval before their acceptance the IS0 Council They are approved least 75 % approval International Metallic by the member Standard (IEC) on all in accordance are circulated with IS0 procedures Standards by Technical Standard for Standardization, Committee ISO/TC is for information 1988 only Printed in Switzerland Copyright International Organization for Standardization Provided by IHS under license with ISO No reproduction or networking permitted without license from IHS to by requiring at coatings Annex A of this International Organization committees as International bodies voting IS0 9220 was prepared and other inorganic international Commission standardization Not for Resale 107, INTERNATIONAL IS0 9220 : 1966 (El STANDARD Metallic coatings - Measurement of coating thickness - Scanning electron microscope method Scope Instrumentation This International Standard specifies a method for the measurement of the local thickness of metallic coatings by 5.1 examination micro- The SEM shall have a resolution of less Suitable of cross-sections scope (SEMI with a scanning It is destructive electron and has an uncertainty than 10 % or 0,l pm, whichever is greater It can be used for thicknesses up to several millimetres, but it is usually more practical to use a light microscope (IS0 5.2 Scanning electron instruments of 50 nm or better are available commercially SEM stage micrometer magnification or graticule is required for calibration of the SEM shall have an uncertainty Normative capability (SEMI 1463) when applicable A stage micrometer microscope employed references Suitable The stage micrometer of the or graticule of less than % for the magnification stage micrometers or graticules are available commercially The following reference standards Standard At the time were valid All standards agreements to contain in this text, constitute provisions of publication, the the editions possibility indicated registers of currently the valid International I SO 1463 : 1992, Metallic and oxide coatings of coating thickness - Microscopical method most recent of IEC and IS0 influencing The following factors the measurement may affect ment of coating thickness 6.1 roughness the accuracy of a measure- Standards Surface Measurement If the coating or its substrate is rough relative to the coating thickness, one or both of the interfaces bounding the coating IS0 2064 : 1990, Metallic and other non-organic coatings Definitions and conventions concerning the measurement of `,,,`-`-`,,`,,`,`,,` - thickness Factors results Standard areencouraged of applying editions of the standards listed below Members maintain through are subject to revision, and parties to based on this International investigate which, provisions of this International cross-section may be too irregular to permit accurate ment of the average thickness 6.2 measure- in the field of view Taper of cross-section If the plane of the cross-section is not perpendicular to the plane of the coating, the measured thickness will be greater Definition than the true thickness For example, an inclination the perpendicular will contribute a 1.5 % error For the purposes of this International definition applies Standard, of IO0 to the following 6.3 local thickness: The mean of the thickness measurements, of which a specified number is made within a reference area (See Specimen tilt Any tilt of the specimen (plane of cross-section) the SEM beam may result in an inaccurate with respect to measurement IS0 2064.) NOTE - If the tilt of the test specimen is different from that used for calibration, inaccuracies may result Principle A test specimen section 6.4 is cut, of the coating ground, and polished for metallographic scanning electron microscope The measurement conventional micrograph or on a photograph waveform from by a is made on a of the video signal for a single scan across the coating Copyright International Organization for Standardization Provided by IHS under license with ISO No reproduction or networking permitted without license from IHS a cross- examination Coating deformation Detrimental deformation of the coating can be caused by excessive temperature or pressure during the mounting and preparation of cross-sections of soft coatings or coatings melt at low temperatures, and by excessive abrasion materials during preparation of cross-sections that of brittle Not for Resale IS0 9220 : 1988 (El 6.5 Rounding If the edge of the coating coating cross-section observed thickness rounding can polishing, or etching 6.6 6.12 of edges of the coating cross-section is rounded, is not completely may differ from be caused i.e if the flat up to its edges, the the true thickness by improper mounting, Edge grinding, during effect is minimized specimen of an SEM may drift with time This by mounting the stage micrometer side by side on the SEM transfer time short 6.12.2 A tronic of the test specimen serves to protect of cross-sections measurement surface 6.12.1 The magnification adjustments edges during preparation an inaccurate of magnification and test stage so as to keep the (see 6.6 and clause A 1) Overplating Overplating Stability Removal preparation the coating and thus to prevent of the coating for overplating material can cause a low thickness measurement change in magnification can are made with the focusing controls; for example voltage and contrast the occur when and other SEM elec- scan rotation, operating controls Such a change is prevented by not using the focus controls or other SEM electronic micrometer scale except to focus using the x, y and z controls of the stage controls Appropriate after photographing manipulation of the the stage x, y and z controls will bring the specimen surface to the focal point of the 6.7 SEM beam Etching Optimum etching will produce a clearly defined and narrow dark line at the interface between the two metals A wide or poorly defined line can result in an inaccurate meaurement 6.13 Stability Dimensional of micrographs changes of micrographs and with temperature micrograph 6.6 Smearing Polishing may between measurement indium, leave smeared two This and gold smearing, repeat metal metals may occur polishing, several times Any significant obscures the true are kept together of the photographic will be minimized If the calibration scale and the micrograph and time is allowed for paper, errors from this source The use of resin-coated paper is advised results in an inaccurate with To help identify the that and can take place with time changes of the stage micrometer of the test specimen stabilization boundarv and humidity soft metals whether etching, variation like lead, or not there and is Preparation of cross-sections measurement in readings is an indica- Prepare the test specimen tion of possible smearing a) the cross-section so that is perpendicular to the plane of the coating; 6.9 Poor contrast The visual contrast their atomic b) between numbers metals in an SEM are close together is poor when For example, bright and semi-bright nickel layers may not be discriminable unless their common boundary can be brought out sufficiently by appropriate binations, backscatter 6.10 etching and SEM techniques energy dispersive X-ray images (see A.3.6) (see A.3.5) or d) can be helpful between deformed by cutting the boundaries of the coating to be or cross-sectioning measurement errors tend of the coating cross-section defined by no more than contrasting narrow, well-defined e) thickness, is flat and the entire width is For some metal com- techniques are sharply appearance, or by a line; if the video waveform signal is to be measured, signal trace is flat except across the two boundaries coating to increase with decreasing magnification If practical, the magnification should be chosen so that the field of view is NOTE - the of the Further guidance is given in annex A 1,5 and times the coating thickness The magnification readout actual magnification for some instruments, of an SEM appropriate often differs from the the magnification has been found to vary errors are minimized Calibration of instruments General Before may not be uniform over the entire field, errors can occur if both the calibration and the measure- ment are not made over the same portion errors can be very significant of the field These Appropriate attention (5.1) shall be calibrated shall be given clause 6, to the procedures with an (5.2) using a photograph as used for the sample to the factors listed in specified in clause 9, and to the un- certainty limits of clause 10 The stability of the calibration be checked at frequent intervals Copyright International Organization for Standardization Provided by IHS under license with ISO No reproduction or networking permitted without license from IHS use, each instrument SEM stage micrometer or graticule taken under the same conditions measurement of magnification Because the magnification 6.1 by use of an SEM stage micrometer Uniformity by more than the % often quoted and, by 25 % across the field Magnification 6.11 c) all material removed; Magnification For a given coating the surface image is simultaneously in focus at the magnification used for the measurement; `,,,`-`-`,,`,,`,`,,` - Not for Resale shall IS0 Photography 9.2.2.2 To measure distance between Photograph minimum the image contrast 8.3 image of signal-to-noise the micrometer scale ratio of to and with using a sufficient for later measurement Measure NOTE - the perpendicular centre-to-centre the lines in the photographed 0.1 mm Use a diffraction distance image to the nearest plate reader or equivalent 8.3 the Repeat the measurement at at least three different the horizontal boundaries of to the nearest 0,l the coatings Make mm using a diffraction the plate device Further guidance is given in annex A Calculate the thickness from the equation where to determine the average spacing Calculation d of magnification the magnification of the measurements certified distance between 1, of the photograph average between by dividing the selected y lines by the is the coating thickness, is the linear distance, is the magnification in micrometres; in millimetres, factor on the micrograph; (see 8.4) the lines: 10 +1000 c Measurement The instrument, uncertainty its calibration, that the uncertainty where less than 10 % or 0,l y measure point of the vertical portions of C&X,000 Y locations at least mm apart on the photograph Calculate coating, for this measurement 8.4 at reader or equivalent between 8.3.2 scan measurements Measurement 8.3.1 the the the inflection 1988 (E) `,,,`-`-`,,`,,`,`,,` - 6.2 9220: and its operation of the coating thickness urn, whichever shall be such measurements is greater is (see A.3.7) is the magnification; 4n is the photograph I, measured (average distance, in millimetres, on the 11 of measurements); is the certified distance, in micrometres Expression of results Express the results in micrometres to the nearest 0,Ol urn, but with three digits if greater than urn Procedure NOTE - This requirement is intended to minimize uncertainty due to rounding of calculated values 9.1 Each instrument with the (5.1) manufacturer’s shall be operated instructions in accordance Appropriate attention shall be given to the factors listed in clause and to the uncertainty requirements of clause 10 12 Test report The test report shall contain at least the following Make a micrograph 9.2 conditions and of the test specimen and instrument make an appropriate image Carry out this step in accordance 9.2.1 Conventional micrograph 9.2.1.1 With sharply defined, the stage micrometer 9.2.1.2 0,l boundaries of make conventional the of the micrograph with 9.2.1 or 9.2.2 coatings micrographs Measure the micrographs to at clearly and least linear measurements this is not practical, the sample preparation the reference to this International b) the measured cl identification d) location of the measurements Standard; value; of the test specimen(s); on the test specimen(s); before and after the test nearest on film or paper If f) any unusual have affected features of the measurements that may the results; may not have been suitable 9.2.2 a) e) the magnification as measured specimen measurements; plate reader or other optical device for making accurate : of the SEM scale and of the test specimen mm using a diffraction information under the same settings as used for the calibration measurement measurement Video waveform signal g) date the measurements h) name of the individual were made; responsible for the measure- ments; 9.2.2.1 Photograph scan across the video waveform the coating stage micrometer cross-section scale Copyright International Organization for Standardization Provided by IHS under license with ISO No reproduction or networking permitted without license from IHS signal for a signal and across the SEM i) tvpe of measurements: video waveform signal conventional micrograph or Not for Resale IS0 9220 : 1988 (E) Annex A (informative) A.0 guidance Introduction The preparation thickness there on the preparation of specimens and measurements are greatly dependent is a variety of suitable on individual techniques of coating techniques available reasonable to specify only one set of techniques, impractical to include all the suitable niques described and It is not and measurement A.2.2 A convenient section is to mount specimen of cross-sections way to check for tapering a small diameter so that the perpendicular parallel to that of the coating of the cross- rod or wire with cross-section If a taper is present, the cross- section of the rod will be elliptical and it is techniques The tech- in this annex are intended for guidance only A.2.3 If the video waveform is important that scratches overpolishing signal scan technique be completely does not selectively is used, it removed remove and that one of the metals more than the other so that the signal scan is distorted A.1 the of the rod is Mounting careful polishing it is unnecessary to use chemical A.3 electron With etches To prevent rounding of the edges of the coating cross-section, the free surface of the coating there is no space between should be supported so that the coating and its support usually achieved by overplating Use of the scanning the coating with at least 10 urn of a metal with a hardness similar to that of the coating The overplate should also give an electron signal different from that of the coating A.3.1 If the image of the cross-section, ventional of the micrograph, coating photographed cally conducting material has to be made electri- to prevent a charge build-up If very soft materials are being prepared, become embedded totally immersing during grinding abrasive particles may This may be minimized by as revealed in a con- is to be measured, cross-section contrast are between parent width of the coating The surface of the mounting microscope This is and if the boundaries revealed the two cross-section solely by materials, the the ap- can vary depending on the contrast and brightness settings The variation can be as great as 10 % without any change in instrument magnification To minimize the resulting uncertainty, adjust the contrast and brightness so that the image shows surface detail of the materials on either side of each boundary abrasive papers in a lubricant during grinding or by using a copious flow of lubricant If abrasive particles become embedded, they may be removed by applying a short, A.3.2 light hand polish with spontaneously metal polish after grinding and before diamond finishing or by one or more cycles of alternate and polishing etching Because changing the magnification with time other instrument the instrument and settings, immediately of an SEM can change can change as a result of it is advisable to calibrate before or after measurement of the test specimen For critical measurements, the average of calibration measurements made before and after measurement of the specimen should be used This ensures that no change in A.2 Grinding and polishing the magnification has occurred and provides information on the precision of the calibration A.2.1 It is essential to keep the cross-section mount perpendicular to the coating porating pieces additional surface of the This is facilitated of a similar metal by incor- in the plastic A.3.3 If the video waveform ment is made of the horizontal mounting near the outer edges, by periodically changing the direction of grinding (rotating through 900), and by keeping the points grinding time and pressure to a minimum this horizontal reference If, before grinding, marks are inscribed on the sides of the mounts, inclination from the horizontal is easily measured any Grind the mounted specimens on suitable abrasive paper, using an acceptable lubricant such as water or white spirit, and apply minimum pressure to avoid bevelling the surface Initial grind- between at the boundaries the horizontal measurements the measure- distance the inflection The between inflection point is halfway traces of the two materials distance brightness settings prefer to measure trace is measured, is independent Because of the contrast and and is precisely defined, some operators the video waveform trace for accurate at higher magnifications A.3.4 of the quently, use grades 240, 320, 500 and 600 without exceeding grinding times of 30 to 40 s on each paper; alter the direction of A.3.5 Many SEMs are equipped with energy dispersive X-ray grinding spectroscopy (EDS) metal coating layers At best the resolution ing should employ specimen profile and to remove by 90° successively microcloth 100 or 180 grade abrasive to reveal the true for each any deformed change with to pm, of paper metal Then Subse- polishing urn, and 0,5 urn diamond is often recommended on For a video waveform trace, select a portion polished specimen that yields a flat, smooth signal urn and is often poorer Copyright International Organization for Standardization Provided by IHS under license with ISO No reproduction or networking permitted without license from IHS which Not for Resale can be helpful in identifying the of EDS is about `,,,`-`-`,,`,,`,`,,` - General IS0 A.3.6 electron The use of backscatter images instead of secondary images can also be helpful in distinguishing metal layers with atomic resolution numbers as close together of 0.1 pm as 1, and with a A.3.7 A comprehensive has not been reported investigation reported a measurement of the SEM stage micrometer measurement of measurement For a thin gold coating, tification uncertainty of the calibration the measurement 9220 : 1999 (El of 0,039 urn for the cer- scale, 0,02 f.tm for the micrographs, of the video waveform errors one laboratory and 0,02 f.tm for signal scan `,,,`-`-`,,`,,`,`,,` - Copyright International Organization for Standardization Provided by IHS under license with ISO No reproduction or networking permitted without license from IHS Not for Resale IS0 9220 : 1999 (E) `,,,`-`-`,,`,,`,`,,` - UDC 621.793 Descriptors: : 531.717 coatings, : 620.187 metal coatings, tests, determination, thickness, thickness measurement Price based on pages Copyright International Organization for Standardization Provided by IHS under license with ISO No reproduction or networking permitted without license from IHS Not for Resale