SIST EN ISO 9220:2022
(Main)Metallic coatings - Measurement of coating thickness - Scanning electron microscope method (ISO 9220:2022)
Metallic coatings - Measurement of coating thickness - Scanning electron microscope method (ISO 9220:2022)
This document specifies a destructive method for the measurement of the local thickness of metallic
and other inorganic coatings by examination of cross-sections with a scanning electron microscope
(SEM). The method is applicable for thicknesses up to several millimetres, but for such thick coatings it
is usually more practical to use a light microscope (see ISO 1463). The lower thickness limit depends on
the achieved measurement uncertainty (see Clause 10).
NOTE The method can also be used for organic layers when they are neither damaged by the preparation of
the cross-section nor by the electron beam during imaging.
Metallische Überzüge - Messung der Schichtdicke - Verfahren mit Rasterelektronenmikroskop (ISO 9220:2022)
Dieses Dokument legt ein zerstörendes Verfahren zur Messung der örtlichen Schichtdicke metallischer Überzüge fest (nachstehend sind auch andere anorganische Überzüge gemeint), in dem Querschnitte mit einem Rasterelektronenmikroskop (REM) untersucht werden. Das Verfahren kann für Schichtdicken bis zu mehreren Millimetern angewendet werden, allerdings ist es für solch dicke Schichten üblicherweise praktischer, ein Lichtmikroskop (ISO 1463) zu verwenden, sofern anwendbar. Die untere Dickengrenze hängt von der erreichten Messunsicherheit (siehe Abschnitt 10) ab.
Revêtements métalliques - Mesurage de l'épaisseur de revêtement - Méthode au microscope électronique à balayage (ISO 9220:2022)
Le présent document spécifie une méthode destructive pour le mesurage de l’épaisseur locale des revêtements métalliques et d’autres revêtements inorganiques par examen de coupes transversales au microscope électronique à balayage (MEB). Cette méthode s’applique aux épaisseurs pouvant atteindre plusieurs millimètres; toutefois, pour les revêtements d’une telle épaisseur, il est généralement plus pratique d’utiliser un microscope optique (voir l’ISO 1463). La limite inférieure de l’épaisseur dépend de l’incertitude de mesure obtenue (voir l’Article 10).
NOTE Cette méthode peut également être utilisée pour les couches organiques lorsqu’elles ne sont endommagées ni par la préparation de la coupe transversale ni par le faisceau d’électrons pendant l’imagerie.
Kovinske prevleke - Merjenje debeline prevleke - Postopek z vrstičnim elektronskim mikroskopom (ISO 9220:2022)
Ta dokument določa porušitveno metodo za merjenje lokalne debeline kovinskih in drugih anorganskih prevlek s pregledom prečnih prerezov z vrstičnim elektronskim mikroskopom (SEM). Postopek se uporablja za debeline do nekaj milimetrov, vendar je za tako debele premaze uporaba svetlobnega mikroskopa običajno bolj praktična (glej standard ISO 1463). Spodnja mejna vrednost debeline je odvisna od dosežene merilne negotovosti (glej točko 10). OPOMBA: Postopek je mogoče uporabiti tudi za organske sloje, če se ne poškodujejo med pripravo prečnih prerezov oziroma jih ne poškoduje elektronski snop med slikanjem.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 9220:2022
01-april-2022
Nadomešča:
SIST EN ISO 9220:1999
Kovinske prevleke - Merjenje debeline prevleke - Postopek z vrstičnim
elektronskim mikroskopom (ISO 9220:2022)
Metallic coatings - Measurement of coating thickness - Scanning electron microscope
method (ISO 9220:2022)
Metallische Überzüge - Messung der Schichtdicke - Verfahren mit
Rasterelektronenmikroskop (ISO 9220:2022)
Revêtements métalliques - Mesurage de l'épaisseur de revêtement - Méthode au
microscope électronique à balayage (ISO 9220:2022)
Ta slovenski standard je istoveten z: EN ISO 9220:2022
ICS:
17.040.20 Lastnosti površin Properties of surfaces
25.220.40 Kovinske prevleke Metallic coatings
SIST EN ISO 9220:2022 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 9220:2022
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SIST EN ISO 9220:2022
EN ISO 9220
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2022
EUROPÄISCHE NORM
ICS 25.220.40 Supersedes EN ISO 9220:1994
English Version
Metallic coatings - Measurement of coating thickness -
Scanning electron microscope method (ISO 9220:2022)
Revêtements métalliques - Mesurage de l'épaisseur de Metallische Überzüge - Messung der Schichtdicke -
revêtement - Méthode au microscope électronique à Verfahren mit Rasterelektronenmikroskop (ISO
balayage (ISO 9220:2022) 9220:2022)
This European Standard was approved by CEN on 19 February 2022.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 9220:2022 E
worldwide for CEN national Members.
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SIST EN ISO 9220:2022
EN ISO 9220:2022 (E)
Contents Page
European foreword . 3
2
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SIST EN ISO 9220:2022
EN ISO 9220:2022 (E)
European foreword
This document (EN ISO 9220:2022) has been prepared by Technical Committee ISO/TC 107 "Metallic
and other inorganic coatings" in collaboration with Technical Committee CEN/TC 262 “Metallic and
other inorganic coatings, including for corrosion protection and corrosion testing of metals and alloys”
the secretariat of which is held by BSI.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by August 2022, and conflicting national standards shall
be withdrawn at the latest by August 2022.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 9220:1994.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 9220:2022 has been approved by CEN as EN ISO 9220:2022 without any modification.
3
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SIST EN ISO 9220:2022
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SIST EN ISO 9220:2022
INTERNATIONAL ISO
STANDARD 9220
Second edition
2022-02
Metallic coatings — Measurement of
coating thickness — Scanning electron
microscope method
Revêtements métalliques — Mesurage de l'épaisseur de revêtement —
Méthode au microscope électronique à balayage
Reference number
ISO 9220:2022(E)
© ISO 2022
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SIST EN ISO 9220:2022
ISO 9220:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
© ISO 2022 – All rights reserved
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SIST EN ISO 9220:2022
ISO 9220:2022(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Instrumentation . 1
5.1 Scanning electron microscope . 1
5.2 Tools to calibrate the length measurement function of the SEM software . 1
6 Factors influencing the measurement results . 2
6.1 Surface roughness . 2
6.2 Taper of cross-section . 2
6.3 Specimen tilt . 2
6.4 Coating deformation . 2
6.5 Rounding of edges of the coating . 2
6.6 Plating a protection layer . 2
6.7 Etching . 2
6.8 Smearing . 3
6.9 Poor contrast . 3
6.10 Magnification . 3
6.11 SEM imaging parameters . 3
7 Preparation of cross-sections . 3
8 Calibration of instruments . 3
8.1 General . 3
8.2 Photography . 4
8.3 Measurement . 4
9 Procedure .4
10 Precision . 4
10.1 General . 4
10.2 Repeatability, r. 4
10.3 Reproducibility limit, R . 5
11 Expression of results . 5
12 Test report . 5
Annex A (informative) General guidance on the preparation and measurement of cross-
sections . 7
Annex B (informative) Details on precision .10
Bibliography .12
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SIST EN ISO 9220:2022
ISO 9220:2022(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee 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.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 107, Metallic and other inorganic coatings,
in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/
TC 262, Metallic and other inorganic coatings, in accordance with the Agreement on technical cooperation
between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 9220:1988), which has been technically
revised.
The main changes are as follows:
— addition of two further calibration methods in 5.2, 8.2, and 8.3;
— deletion of technically outdated content concerning instability of SEMs and analogue photos or
concerning the operation of SEMs [removal of old Subclauses 6.11, 6.12, 6.13, 8.4, 9.2.1, 9.2.2, 9.3,
A.2.3, A.3.2, A.3.3, A.3.4, and A.3.7; revision of item e) in Clause 12];
— discussion of influences of imaging parameters on measurement uncertainty (new 6.11);
— revision of Clause 10 and addition of Annex B with precision data from round robin tests;
— revision of Annex A to (re-) align it with ISO 1463:2021;
— adding a bibliography with informative references.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
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SIST EN ISO 9220:2022
INTERNATIONAL STANDARD ISO 9220:2022(E)
Metallic coatings — Measurement of coating thickness —
Scanning electron microscope method
1 Scope
This document specifies a destructive method for the measurement of the local thickness of metallic
and other inorganic coatings by examination of cross-sections with a scanning electron microscope
(SEM). The method is applicable for thicknesses up to several millimetres, but for such thick coatings it
is usually more practical to use a light microscope (see ISO 1463). The lower thickness limit depends on
the achieved measurement uncertainty (see Clause 10).
NOTE The method can also be used for organic layers when they are neither damaged by the preparation of
the cross-section nor by the electron beam during imaging.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
local thickness
mean of the thickness measurements, of which a specified number is made within a reference area
[SOURCE: ISO 2064:1996, 3.4]
4 Principle
A test specimen is cut, ground, and polished from a cross-section of the coating for materialographic
examination by a scanning electron microscope. The measurement is made on the digital image
generated by the SEM using either the tools of the SEM’s operating software or by importing the image
file together with its calibration data into an image processing software and using that software’s tools.
5 Instrumentation
5.1 Scanning electron microscope
Suitable instruments are available commercially.
5.2 Tools to calibrate the length measurement function of the SEM software
Suitable tools are required for the calibration of the length measurement function of the SEM’s
software, e.g. a stage micrometre, or a graticule, or a piece from a silicon wafer with a regular pattern
of (cylindrical) metallic bumps with a certified distance of the cylinder axes, or spherical polymer
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SIST EN ISO 9220:2022
ISO 9220:2022(E)
particles of certified diameter in the range of a few tenths of a micrometre to a few micrometres can be
used, all of which are commercially available. They should have an uncertainty of less than 5 %.
6 Factors influencing the measurement results
6.1 Surface roughness
If the coating or its substrate is rough relative to the coating thickness, one or both of the interfaces of
the coating cross-section can be too irregular to permit accurate measurement of the average thickness
in the field of view. In this case, it can be helpful to use software solutions, which can identify the
boundary lines of the coating and either determine its area and divide it by the image width or place
automatically, for example, 100 measurement lines in order to calculate an average coating thickness.
6.2 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 than the true thickness. For example, an inclination of 10° to the perpendicular will
contribute a 1,5 % error.
NOTE This source of error is also known as cosine error in the small-angle approximation.
6.3 Specimen tilt
Any tilt of the specimen (plane of cross-section) with respect to the SEM beam can result in an
inaccurate measurement.
NOTE 1 If the tilt of the test specimen is different from that used for calibration, inaccuracies can result.
NOTE 2 This source of error is also known as cosine error in the small-angle approximation.
6.4 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 that melt at low temperatures,
and by excessive abrasion of brittle materials during preparation of cross-sections.
6.5 Rounding of edges of the coating
If the edge of the coating cross-section is rounded, i.e. if the coating cross-section is not completely flat
up to its edges, the observed thickness can differ from the true thickness. Edge rounding can be caused
by improper mounting, grinding, polishing, or etching (see 6.6 and A.2).
6.6 Plating a protection layer
Overplating of the test specimen, i.e. plating a protection layer onto the test specimen, serves to protect
the coating edges during preparation of cross-sections and thus to prevent an inaccurate measurement.
Removal of the coating material during surface preparation for overplating can cause a low thickness
measurement.
6.7 Etching
Optimum etching will produce a clearly defined and narrow dark line at the interface between the two
materials. A wide or poorly defined line can result in an inaccurate measurement.
NOTE Etching is usually applied for the microscopic method (see ISO 1463) and can be useful for relatively
thick coatings in the SEM, too, especially when individual layers from the same material need to be distinguished
and there is no or too weak material contrast in the back scattered electron image (see 6.9). For (very) thin
coatings, etching has often a negative effect on the measurement uncertainty.
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SIST EN ISO 9220:2022
ISO 9220:2022(E)
6.8 Smearing
Polishing can leave smeared metal that obscures the true boundary between two metals and results
in an inaccurate measurement. This can occur with soft metals like indium or gold. To help identify
whether or not there is smearing, repeat the polishing, etching, and measurement several times. Any
significant variation in readings is an indication of possible smearing.
6.9 Poor contrast
The visual contrast between metals in an SEM is poor when their atomic numbers are close together. For
example, bright and semi-bright nickel layers cannot be discriminable unless their common boundary
can be brought out sufficiently by appropriate etching (see 6.7) and SEM techniques.
6.10 Magnification
For a given coating thickness, measurement errors tend to increase with decreasing magnification.
If practical, the magnification should be chosen so that the field of view is between 1,5 and 3 times
the coating thickness. For very thin coatings this is often not practicable; then choose the maximum
magnification at which the image of the coating and its boundaries appears still “sharp”.
6.11 SEM imaging parameters
The acceleration voltage of the SEM can influence the appearance of the coating in the image. For
example, a higher acceleration voltage causes a higher depth from which the signal is collected and can
lead to not clearly discernible edges, e.g. at a metal to polymer (e.g. molding resin) interface.
High probe currents can improve the brightness and contrast of the image and increase count rates for
energy-dispersive X-ray spectroscopy (EDS), but can at the same time reduce the resolution and thus
increase measurement uncertainty.
The settings of brightness, contrast and gamma can influence the appearance of the coating in the
image and – especially for thin coatings – the measured thickness.
7 Preparation of cross-sections
Prepare the test specimen so that:
a) the cross-section is perpendicular to the plane of the coating;
b) the surface is flat and the entire width of the coating image is simultaneously in focus at the
magnification to be used for the measurement;
c) all material deformed by cutting or cross-sectioning is removed;
d) the boundaries of the coating cross-section are sharply defined by no more than contrasting
appearance, or by a narrow, well-defined line.
NOTE Further guidance is given in Annex A.
8 Calibration of instruments
8.1 General
Before use, each instrument (5.1) shall be calibrated with an appropriate tool (5.2) under the same
conditions as used for the sample measurement.
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SIST EN ISO 9220:2022
ISO 9220:2022(E)
Appropriate attention shall be given to the factors listed in Clause 6, to the procedures specified in
Clause 9 and to the uncertainty limits of Clause 10. The stability of the calibration shall be checked at
regular intervals.
8.2 Photography
Capture an image of the certified calibration standard, e.g. the micrometre scale, the graticule, 10 × 10
to 15 × 15 of the metallic bumps in top view or of some of the spherical particles (5.2) with sufficient
contrast for later measurement.
Spherical particles (5.2) brought from a suspension onto a clean SEM sample stub tend to agglomerate.
Search isolated particles on the sample stub to record the images for calibration. An inappropriate
choice of imaging parameters (6.11) can let the calibration fail.
8.3 Measurement
8.3.1 Using the tools of the SEM’s software or using a separate image analysis software, to which
the image file and its calibration data were imported, measure the left-to-left or right-to-right distance
between the lines of the stage micrometre or the graticule (5.2) or the diameter of the spherical
particles (5.2).
8.3.2 Repeat the measurement at minimum three different locations over the entire field of the image.
8.3.3 The image of the metallic bumps (5.2) needs to be analysed with a software, which can fit
circles to the top view of the cylindrical bumps and then determine the distance of their centres.
9 Procedure
9.1 Each instrument (5.1) shall be operated in accordance with the manufacturer's instructions.
Appropriate attention shall be given to the factors listed in Clause 6 and to the uncertainty requirements
of Clause 10.
9.2 Capture an image of the test specimen under the same conditions and instrument settings
used for the calibration. The boundaries of the coatings shall be clearly and sharply defined. Make
an appropriate measurement using the tools of the SEM’s software or in a separate image analysis
software, to which the image file and its calibration data were imported.
10 Precision
10.1 General
See Annex B for further information on determining precision.
10.2 Repeatability, r
Repeatability, r, is the value less than or equal to which the absolute difference between two test results
obtained under repeatability conditions may be expected to be, with a probability of 95 % (according to
ISO 5725-1:1994, 3.16). The repeatability limit, r, in accordance with this document and calculated with
a probability of 95 %, is given in Table 1 for typical applications of this measurement technique.
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SIST EN ISO 9220:2022
ISO 9220:2022(E)
Table 1 — Repeatability limit, r
Application Thickness Repeatability limit
t r
μm μm
Cross-section of a Ti coat-
≈1 ≈0,05
ing on a Si wafer
Cross-section of a polyim-
≈14 ≈0,5
ide foil
Cross-section of a polyim-
≈25 ≈0,5
ide foil
10.3 Reproducibility limit, R
Reproducibility limit, R, is the value less than or equal to which the absolute difference between two
test results obtained under reproducibility conditions may be expected to be, with a probability of 95 %
(according to ISO 5725-1:1994, 3.20). The reproducibility limit, R, in accordance with this document and
calculated with a probability of 95 %, is given in Table 2 for typical applications of this measurement
technique.
Table 2 — Reproducibility limit, R
Application Thickness Reproducibility limit
t R
μm μm
Cross-section of a Ti coat-
≈1 ≈0,12
ing on a Si wafer
Cross-section of a polyim-
≈14 ≈2,0
ide foil
Cross-section of a polyim-
≈25 ≈2,0
ide foil
11 Expression of results
Depending on the coating thickness and at the operator’s convenience, express the results either in
millimetres, micrometres, or nanometres with one more digit than significant to prevent rounding
errors when calculating statistics.
12 Test report
The test report shall contain at least the following information:
a) a reference to this document, i.e. ISO 9220:2022;
b) the measured value;
c) identification of the test specimen(s);
d) location of the measurements on the test specimen;
e) a scale bar or an information about the image width superimposed on the SEM image;
f) any unusual features of the measurements that can have affected the results;
g) any deviations from the procedure described in this document;
h) date the measurements were made;
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SIST EN ISO 9220:2022
ISO 9220:2022(E)
i) name of the individual respon
...
SLOVENSKI STANDARD
oSIST prEN ISO 9220:2021
01-maj-2021
Kovinske prevleke - Merjenje debeline prevleke - Postopek z vrstičnim
elektronskim mikroskopom (ISO/DIS 9220:2021)
Metallic coatings - Measurement of coating thickness - Scanning electron microscope
method (ISO/DIS 9220:2021)
Metallische Überzüge - Messung der Schichtdicke - Verfahren mit
Rasterelektronenmikroskop (ISO/DIS 9220:2021)
Revêtements métalliques - Mesurage de l'épaisseur de revêtement - Méthode au
microscope électronique à balayage (ISO/DIS 9220:2021)
Ta slovenski standard je istoveten z: prEN ISO 9220
ICS:
17.040.20 Lastnosti površin Properties of surfaces
25.220.40 Kovinske prevleke Metallic coatings
oSIST prEN ISO 9220:2021 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN ISO 9220:2021
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oSIST prEN ISO 9220:2021
DRAFT INTERNATIONAL STANDARD
ISO/DIS 9220
ISO/TC 107 Secretariat: KATS
Voting begins on: Voting terminates on:
2021-03-24 2021-06-16
Metallic coatings — Measurement of coating thickness —
Scanning electron microscope method
Revêtements métalliques — Mesurage de l'épaisseur de revêtement — Méthode au microscope
électronique à balayage
ICS: 25.220.40
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 9220:2021(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
©
PROVIDE SUPPORTING DOCUMENTATION. ISO 2021
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oSIST prEN ISO 9220:2021
ISO/DIS 9220:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
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oSIST prEN ISO 9220:2021
ISO/DIS 9220:2021(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Instrumentation . 1
5.1 Scanning electron microscope (SEM) . 1
5.2 Tools to calibrate the length measurement function of the SEM software . 2
6 Factors influencing the measurement results . 2
6.1 Surface roughness . 2
6.2 Taper of cross-section . 2
6.3 Specimen tilt . 2
6.4 Coating deformation . 2
6.5 Rounding of edges of the coating . 2
6.6 Overplating . 2
6.7 Etching . 3
6.8 Smearing . 3
6.9 Poor contrast . 3
6.10 Magnification . 3
6.11 SEM imaging parameters . 3
7 Preparation of cross-sections . 3
8 Calibration of instruments . 4
8.1 General . 4
8.2 Photography . 4
8.3 Measurement . 4
9 Procedure. 4
10 Precision . 4
10.1 General . 4
10.2 Repeatability (r) . 4
10.3 Reproducibility limit (R) . 5
11 Expression of results . 5
12 Test report . 5
Annex A (informative) General guidance on the preparation and measurement of cross-sections .7
Annex B (informative) Details on precision .10
Bibliography .12
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oSIST prEN ISO 9220:2021
ISO/DIS 9220:2021(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee 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.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 107, Metallic and other inorganic coatings.
This second edition cancels and replaces the first edition (ISO 9220:1988), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— Addition of two further calibration methods in 5.2, 8.2, and 8.3;
— Deletion of technically outdated content concerning instability of SEMs and analog photos or
concerning the operation of SEMs [removal of old Subclauses 6.11, 6.12, 6.13, 8.4, 9.2.1, 9.2.2, 9.3,
A.2.3, A.3.2, A.3.3, A.3.4, and A.3.7; revision of item e) in Clause 12];
— Discussion of influences of imaging parameters on measurement uncertainty (new Subclause 6.11);
— Revision of Clause 10 and addition of Annex B with precision data from round robin tests;
— Revision of Annex A to (re-) align it with ISO 1463:2021;
— Adding a bibliography with informative references.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
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oSIST prEN ISO 9220:2021
DRAFT INTERNATIONAL STANDARD ISO/DIS 9220:2021(E)
Metallic coatings — Measurement of coating thickness —
Scanning electron microscope method
1 Scope
This document specifies a destructive method for the measurement of the local thickness of metallic
coatings (hereafter also other inorganic coatings are meant) by examination of cross-sections with a
scanning electron microscope (SEM). The method can be used for thicknesses up to several millimetres,
but for such thick coatings it is usually more practical to use a light microscope (ISO 1463) when
applicable. The lower thickness limit depends on the achieved measurement uncertainty (see Clause 10).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 1463, Metallic and oxide coatings — Measurement of coating thickness – Microscopical method
ISO 2064, Metallic and other non-organic coatings — Definitions and conventions concerning the
measurement of thickness
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
local thickness
mean of the thickness measurements, of which a specified number is made within a reference area
[SOURCE: ISO 2064:1996, 3.4]
4 Principle
A test specimen is cut, ground, and polished from a crosssection of the coating for metallographic
examination by a scanning electron microscope. The measurement is made on the digital image
generated by the SEM using either the tools of the SEM’s operating software or by importing the image
file together with its calibration data into an image processing software and using that software’s tools.
5 Instrumentation
5.1 Scanning electron microscope (SEM)
Suitable instruments are available commercially.
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oSIST prEN ISO 9220:2021
ISO/DIS 9220:2021(E)
5.2 Tools to calibrate the length measurement function of the SEM software
Suitable tools are required for the calibration of the length measurement function of the SEM’s
software. Either a stage micrometer, or a graticule, or a piece from a silicon wafer with a regular pattern
of (cylindrical) metallic bumps with a certified distance of the cylinder axes, or spherical polymer
particles of certified diameter in the range of a few tenths of a micrometer to a few micrometers can be
used, all of which are commercially available. They shall have an uncertainty of less than 5 %.
6 Factors influencing the measurement results
6.1 Surface roughness
If the coating or its substrate is rough relative to the coating thickness, one or both of the interfaces
bounding the coating cross-section may be too irregular to permit accurate measurement of the average
thickness in the field of view. In this case it can be helpful to use software solutions, which can identify
the boundary lines of the coating and either determine its area and divide it by the image width or place
automatically e. g. 100 measurement lines in order to calculate an average coating thickness.
6.2 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 than the true thickness. For example, an inclination of 10° to the perpendicular will
contribute a 1.5 % error.
NOTE This source of error is also known as cosine error in the small-angle approximation.
6.3 Specimen tilt
Any tilt of the specimen (plane of cross-section) with respect to the SEM beam may result in an
inaccurate measurement.
NOTE 1 If the tilt of the test specimen is different from that used for calibration, inaccuracies may result.
NOTE 2 This source of error is also known as cosine error in the small-angle approximation.
6.4 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 that melt at low temperatures,
and by excessive abrasion of brittle materials during preparation of cross-sections.
6.5 Rounding of edges of the coating
If the edge of the coating cross-section is rounded, i.e. if the coating cross-section is not completely flat
up to its edges, the observed thickness may differ from the true thickness. Edge rounding can be caused
by improper mounting, grinding, polishing, or etching (see 6.6 and A.1).
6.6 Overplating
Overplating of the test specimen serves to protect the coating edges during preparation of cross-
sections and thus to prevent an inaccurate measurement. Removal of the coating material during
surface preparation for overplating can cause a low thickness measurement.
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oSIST prEN ISO 9220:2021
ISO/DIS 9220:2021(E)
6.7 Etching
Optimum etching will produce a clearly defined and narrow dark line at the interface between the two
materials. A wide or poorly defined line can result in an inaccurate measurement.
NOTE Etching is usually applied for the microscopic method (ISO 1463) and can be useful for relatively thick
coatings in the SEM, too, especially when individual layers from the same material need to be distinguished and
there is no or too weak material contrast in the back scattered electron image (6.9). For (very) thin coatings
etching has often a negative effect on the measurement uncertainty.
6.8 Smearing
Polishing may leave smeared metal that obscures the true boundary between two metals and results
in an inaccurate measurement. This may occur with soft metals like indium or gold. To help identify
whether or not there is smearing, repeat the polishing, etching, and measurement several times. Any
significant variation in readings is an indication of possible smearing.
6.9 Poor contrast
The visual contrast between metals in an SEM is poor when their atomic numbers are close together. For
example, bright and semi-bright nickel layers may not be discriminable unless their common boundary
can be brought out sufficiently by appropriate etching (6.7) and SEM techniques.
6.10 Magnification
For a given coating thickness, measurement errors tend to increase with decreasing magnification.
If practical, the magnification should be chosen so that the field of view is between 1.5 and 3 times
the coating thickness. For very thin coatings this is often not practicable; then choose the maximum
magnification at which the image of the coating and its boundaries appears still “sharp”.
6.11 SEM imaging parameters
The acceleration voltage of the SEM can influence the appearance of the coating in the image. For
example, a higher acceleration voltage causes a higher depth from which the signal is collected and can
lead to not clearly discernible edges, e. g. at a metal to polymer (e. g. molding resin) interface.
High probe currents can improve the brightness and contrast of
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