SIST EN IEC 60068-2-82:2019
(Main)Environmental testing - Part 2-82: Tests - Test Xw1: Whisker test methods for components and parts used in electronic assemblies
Environmental testing - Part 2-82: Tests - Test Xw1: Whisker test methods for components and parts used in electronic assemblies
IEC 60068-2-82:2019 specifies tests for the whiskering propensity of surface finishes of electric or electronic components and mechanical parts such as punched/stamped parts (for example, jumpers, electrostatic discharge protection shields, mechanical fixations, press‑fit pins and other mechanical parts used in electronic assemblies) representing the finished stage, with tin or tin-alloy finish. Changes of the physical dimensions of mould compounds, plastics and the like during the required test flow are not considered or assessed. The test methods have been developed by using a knowledge-based approach.
This edition includes the following significant technical changes with respect to the previous edition:
– extension of the scope of the test standard from electronic to electromechanic components and press-fit pins, which are used for assembly and interconnect technology;
– significant reduction of the testing effort by a knowledge-based selection of test conditions i.e. tests not relevant for a given materials system can be omitted (see Annex D);
– harmonization with JESD 201A by omission of severities M, N for temperature cycling tests;
– highly reduced test duration (1 000 h instead of 4 000 h) for damp-heat test by introducing test condition at elevated humidity of 85 % R.H. and a temperature of 85 °C providing increased severity.
Umgebungseinflüsse - Teil 2-82: Prüfungen - Prüfung XW1: Whisker-Prüfverfahren für elektronische und elektrische Bauelemente
Essais d’environnement - Partie 2-82: Essais - Essai XW1: Méthodes de vérification des trichites pour les composants électroniques et électriques
L'IEC 60068-2-82:2019 spécifie des essais de vérification de la propension au développement des trichites pour les finis de surface des composants électriques ou électroniques et des pièces mécaniques comme les pièces embouties/estampées (par exemple cavaliers, écrans de protection contre les décharges électrostatiques, fixations mécaniques, contacts insérés à force et autres pièces mécaniques utilisées dans les ensembles électroniques) qui représentent la phase de finition, avec un fini en étain ou en alliage d'étain. Les modifications des dimensions physiques des composants moulés, des plastiques et autres pendant le flux d'essai exigé ne sont pas prises en compte ni évaluées. Les méthodes d'essai ont été mises au point en utilisant une approche fondée sur la connaissance.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
– extension du domaine d'application de la norme d'essai des composants électroniques aux composants électromécaniques et aux contacts insérés à force qui sont utilisés pour la technologie d'assemblage et d'interconnexion;
– réduction significative de l'effort d'essai par une sélection de conditions d'essai fondée sur la connaissance, c'est-à-dire que les essais non applicables à un système de matériaux donné peuvent être omis (voir Annexe D);
– harmonisation avec la JESD 201A par omission des sévérités M et N pour les essais de cycle thermique;
– réduction considérable de la durée d'essai (1 000 h au lieu de 4 000 h) pour l'essai de chaleur humide par l'introduction d'une condition d'essai à humidité élevée de 85 % H.R. et d'une température de 85 °C assurant une plus grande sévérité.
Okoljsko preskušanje - 2-82. del: Preskusi - Preskus Xw1: Preskusna metoda za nitke v komponentah pri elektronskih sestavih
Ta del standarda IEC 60068 določa preskuse nagnjenosti k tvorjenju vlaknastih kristalov, ki se lahko pojavijo na prevlekah električnih ali elektronskih komponent in mehanskih delov, kot so vgravirani/vtisnjeni deli (na primer povezovalni vodi, zaščite pred elektrostatičnimi razelektritvami, mehanske pritrditve, zatič za pritrditev s pritiskom ter drugi mehanski deli, ki se uporabljajo v elektronskih sklopih) in predstavljajo zaključno fazo, s prevleko iz kositra ali kositrove zlitine. Spremembe fizičnih mer kalupnih mas, polimerov in podobnega med zahtevanim preskušanjem niso obravnavane ali ocenjene. Preskusne metode so bile razvite z na znanju temelječim pristopom.
Ta dokument lahko uporabljajo tudi poddobavitelji, na primer delavnice za prevleke, delavnice za vtiskavanje ali drugi ponudniki storitev za zagotavljanje enakomerne kakovosti površine v oskrbovalni verigi.
Te preskusne metode se uporabljajo z opredeljenimi kriteriji sprejemljivosti, če jih predpisuje ustrezna specifikacija komponente ali uporabe.
Preskusi, ki so opisani v tem dokumentu, se uporabljajo za temeljno kvalifikacijo, redno spremljanje skladno s točko 7 in za spremembe v tehnologiji ali proizvodnih postopkih obstoječih površin skladno s točko 9.
Ta preskusna metoda ne zajema priključnega dela konektorjev. Za priključne dele konektorjev se uporablja IEC 60512-16-21.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-september-2019
Nadomešča:
SIST EN 60068-2-82:2007
Okoljsko preskušanje - 2-82. del: Preskusi - Preskus Xw1: Preskusna metoda za
nitke v komponentah pri elektronskih sestavih
Environmental testing - Part 2-82: Tests - Test Xw1: Whisker test methods for
components and parts used in electronic assemblies
Umgebungseinflüsse - Teil 2-82: Prüfungen - Prüfung XW1: Whisker-Prüfverfahren für
elektronische und elektrische Bauelemente
Essais d’environnement - Partie 2-82: Essais - Essai XW1: Méthodes de vérification des
trichites pour les composants électroniques et électriques
Ta slovenski standard je istoveten z: EN IEC 60068-2-82:2019
ICS:
19.040 Preskušanje v zvezi z Environmental testing
okoljem
31.190 Sestavljeni elektronski Electronic component
elementi assemblies
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD EN IEC 60068-2-82
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2019
ICS 19.040 Supersedes EN 60068-2-82:2007
English Version
Environmental testing - Part 2-82: Tests - Test Xw1: Whisker test
methods for components and parts used in electronic
assemblies
(IEC 60068-2-82:2019)
Essais d'environnement - Partie 2-82: Essais - Essai Xw1: Umgebungseinflüsse - Teil 2-82: Prüfungen - Prüfung XW1:
Méthodes de vérification des trichites pour les composants Whisker-Prüfverfahren für Bauelemente und Teile in
et les pièces utilisés dans les ensembles électroniques elektronischen Baugruppen
(IEC 60068-2-82:2019) (IEC 60068-2-82:2019)
This European Standard was approved by CENELEC on 2019-06-18. CENELEC 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 CENELEC 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 CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2019 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 60068-2-82:2019 E
European foreword
The text of document 91/1562/FDIS, future edition 2 of IEC 60068-2-82, prepared by IEC/TC 91 "Electronics
assembly technology" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
The following dates are fixed:
• latest date by which the document has to be implemented at national level by (dop) 2020-03-18
publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2022-06-18
document have to be withdrawn
This document supersedes EN 60068-2-82:2007.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Endorsement notice
The text of the International Standard IEC 60068-2-82:2019 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
IEC 61191-1 NOTE Harmonized as EN IEC 61191-1
IEC 61249-2-7 NOTE Harmonized as EN 61249-2-7
IEC 61249-2-22 NOTE Harmonized as EN 61249-2-22
IEC 61249-2-35 NOTE Harmonized as EN 61249-2-35
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE 1 Where an International Publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies.
NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available here: www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 60068-1 2013 Environmental testing - Part 1: General and EN 60068-1 2014
guidance
IEC 60068-2-14 2009 Environmental testing - Part 2-14: Tests - Test EN 60068-2-14 2009
N: Change of temperature
IEC 60068-2-20 - Environmental testing - Part 2-20: Tests - Test EN 60068-2-20 -
T: Test methods for solderability and
resistance to soldering heat of devices with
leads
IEC 60068-2-58 - Environmental testing - Part 2-58: Tests - Test EN 60068-2-58 -
Td: Test methods for solderability, resistance
to dissolution of metallization and to soldering
heat of surface mounting devices (SMD)
IEC 60068-2-67 - Environmental testing - Part 2-67: Tests - Test EN 60068-2-67 -
Cy: Damp heat, steady state, accelerated test
primarily intended for components
IEC 60068-2-78 - Environmental testing - Part 2-78: Tests - Test EN 60068-2-78 -
Cab: Damp heat, steady state
IEC 60512-16-21 2012 Connectors for electronic equipment - Tests EN 60512-16-21 2012
and measurements - Part 16-21: Mechanical
tests on contacts and terminations - Test 16u:
Whisker test via the application of external
mechanical stresses
IEC 61192-3 2002 Workmanship requirements for soldered EN 61192-3 2003
electronic assemblies - Part 3: Through-hole
mount assemblies
IEC 60068-2-82 ®
Edition 2.0 2019-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Environmental testing –
Part 2-82: Tests – Test Xw : Whisker test methods for components and parts
used in electronic assemblies
Essais d'environnement –
Partie 2-82: Essais – Essai Xw : Méthodes de vérification des trichites
pour les composants et les pièces utilisés dans les ensembles électroniques
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 19.040 ISBN 978-2-8322-6863-6
– 2 – IEC 60068-2-82:2019 © IEC 2019
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Test equipment . 9
4.1 General . 9
4.2 Desiccator . 9
4.3 Humidity chamber . 9
4.4 Thermal cycling chamber . 9
4.5 Equipment for visual inspection . 9
4.5.1 Scanning electron microscope . 9
4.5.2 Optical microscope/Confocal laser microscope . 9
4.6 Fixing jig . 9
5 Preparation for test . 10
5.1 Selection of relevant tests . 10
5.1.1 General . 10
5.1.2 Storage conditions prior to testing . 11
5.1.3 Pre-aging (storage in the supply chain) before testing . 12
5.2 Handling of the specimens . 12
5.3 Sample size . 12
5.4 Surface and base materials for test selection . 12
5.5 Preconditioning of test specimen not intended for soldering/welding . 13
5.5.1 Preconditioning of test specimen intended for press-fit applications . 13
5.5.2 Preconditioning of test specimen intended for mechanical loads other
than press fit . 14
5.6 Preconditioning of test specimen intended for soldering/welding . 14
5.6.1 General . 14
5.6.2 Mechanical pretreatment . 14
5.6.3 Heat pre-treatment . 15
6 Test conditions . 15
6.1 General . 15
6.2 Ambient test . 15
6.3 Damp heat test . 15
6.4 Temperature cycling test . 16
6.5 Ambient test for press-fit applications . 16
7 Monitoring and technological similarity . 17
7.1 Monitoring . 17
7.2 Technological similarity . 17
8 Test and assessment . 18
8.1 Whisker investigation . 18
8.2 Initial measurement . 18
8.3 Test . 18
8.4 Recovery . 18
8.5 Intermediate or final assessment for each test condition . 18
8.5.1 Fixed threshold length for pass/fail classification . 18
8.5.2 Statistical assessment of whisker lengths . 19
IEC 60068-2-82:2019 © IEC 2019 – 3 –
9 Technology or manufacturing process changes . 19
10 Content of final report . 20
Annex A (normative) Measurement of whisker length . 22
Annex B (informative) Examples of whiskers . 23
Annex C (informative) Guidance on acceptance criteria . 25
C.1 Risks attributed to whiskers . 25
C.2 Acceptance criteria for whisker length . 25
C.3 Acceptance criteria for whisker density . 26
C.4 Statistical evaluation of number and length of whiskers. 26
C.5 Example of statistic evaluation . 26
Annex D (informative) Technical background of whisker growth . 29
Annex E (normative) Transition scenarios for the changeover of the damp-heat test
conditions . 30
Bibliography . 32
Figure 1 – Cross-sectional views of component termination surface finishes . 8
Figure 2 – Selection of test methods . 11
Figure 3 – . 14
Flow for treatment and/or bending and heat treatment
Figure A.1 – Estimation of whisker length . 22
Figure A.2 – Example for whisker length measurement . 22
Figure B.1 – Nodule . 23
Figure B.2 – Column whisker . 23
Figure B.3 – Filament whisker . 24
Figure B.4 – Kinked whisker . 24
Figure B.5 – Spiral whisker . 24
Figure C.1 – Smallest distance of components and circuit boards . 25
Figure C.2 – Histogram of whisker lengths and fitted log-normal distribution . 27
Figure C.3 – Histogram of whisker lengths and fitted log-normal distribution . 28
Figure C.4 – Histogram of whisker lengths and fitted log-normal distribution . 28
Figure E.1 –Transition paths for damp-heat testing of components . 30
Table 1 – Material systems recognized for effective whisker mitigation . 13
Table 2 –
Preconditioning conditions and test legs for components for different
............................................................................................................. 15
assembly processes
Table 3 – Conditions for the ambient test . 15
Table 4 – Conditions for the damp heat test . 16
Table 5 – Conditions for the ambient test . 16
Table 6 – Conditions for the ambient test applicable to press-fit terminations . 17
Table 7 – Classification for measured whisker length . 19
Table 8 – Surface finish technology and manufacturing process change acceptance
parameters . 19
Table 9 – Final report . 21
Table C.1 – Classification for measured whisker length . 27
Table E.1 – Conclusion matrix for parallel damp heat testing . 31
– 4 – IEC 60068-2-82:2019 © IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ENVIRONMENTAL TESTING –
Part 2-82: Tests – Test Xw1: Whisker test methods for components
and parts used in electronic assemblies
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as "IEC
Publication(s)"). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60068-2-82 has been prepared by IEC technical committee 91:
Electronics assembly technology.
This second edition cancels and replaces the first edition published in 2007. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
– extension of the scope of the test standard from electronic to electromechanic components
and press-fit pins, which are used for assembly and interconnect technology;
– significant reduction of the testing effort by a knowledge-based selection of test conditions
i.e. tests not relevant for a given materials system can be omitted (see Annex D);
– harmonization with JESD 201A by omission of severities M, N for temperature cycling
tests;
IEC 60068-2-82:2019 © IEC 2019 – 5 –
– highly reduced test duration (1 000 h instead of 4 000 h) for damp-heat test by introducing
test condition at elevated humidity of 85 % R.H. and a temperature of 85 °C providing
increased severity.
The text of this International Standard is based on the following documents:
FDIS Report on voting
91/1562/FDIS 91/1573/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
A list of all parts in the IEC 60068 series, published under the general title Environmental
testing, can be found on the IEC website.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – IEC 60068-2-82:2019 © IEC 2019
ENVIRONMENTAL TESTING –
Part 2-82: Tests – Test Xw1: Whisker test methods for components
and parts used in electronic assemblies
1 Scope
This part of IEC 60068 specifies tests for the whiskering propensity of surface finishes of
electric or electronic components and mechanical parts such as punched/stamped parts (for
example, jumpers, electrostatic discharge protection shields, mechanical fixations, press-fit
pins and other mechanical parts used in electronic assemblies) representing the finished
stage, with tin or tin-alloy finish. Changes of the physical dimensions of mould compounds,
plastics and the like during the required test flow are not considered or assessed. The test
methods have been developed by using a knowledge-based approach.
This document can also be used at sub-suppliers, like plating shops, stamping shops or other
service providers to ensure a consistent surface quality within the supply chain.
These test methods are employed with defined acceptance criteria by a relevant component
or application specification.
The tests described in this document are applicable for initial qualification, for periodic
monitoring in accordance with Clause 7, and for changes of technology or manufacturing
processes of existing surfaces in accordance with Clause 9.
The mating area of connectors is not covered by this test method. IEC 60512-16-21 applies
for the mating areas of connectors.
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.
IEC 60068-1:2013, Environmental testing – Part 1: General and guidance
IEC 60068-2-14:2009, Environmental testing – Part 2-14: Tests – Test N: Change of
temperature
IEC 60068-2-20, Environmental testing – Part 2-20: Tests – Test T: Test methods for
solderability and resistance to soldering heat of devices with leads
IEC 60068-2-58, Environmental testing – Part 2-58: Tests – Test Td: Test methods for
solderability, resistance to dissolution of metallization and to soldering heat of surface
mounting devices (SMD)
IEC 60068-2-67, Environmental testing – Part 2-67: Tests – Test Cy: Damp heat, steady state,
accelerated test primarily intended for components
IEC 60068-2-78, Environmental testing – Part 2-78: Tests – Test Cab: Damp heat, steady
state
IEC 60068-2-82:2019 © IEC 2019 – 7 –
IEC 61192-3:2002, Workmanship requirements for soldered electronic assemblies – Part 3:
Through-hole mount assemblies
IEC 60512-16-21:2012, Connectors for electronic equipment – Tests and measurements –
Part 16-21: Mechanical tests on contacts and terminations – Test 16u: Whisker test via the
application of external mechanical stresses
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:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
whisker
metallic protrusion that grows spontaneously during storage or use
Note 1 to entry: Whiskers typically do not require any electrical field for their growth and are not to be confused
with products of electrochemical migration. Signs of whiskers include:
– striations in growth direction;
– typically no branching;
– typically constant diameters.
Exceptions are known, but are rare and can require detailed investigation.
For the purposes of this document, whiskers are considered if:
– they have an aspect ratio (length/width) greater than 2;
– they have a length of 10 µm or more.
Note 2 to entry: For the purposes of this document, whiskers have the following characteristics
(see also Annex B):
– they can be kinked, bent, or twisted; they usually have a uniform cross-sectional shape;
– they may have rings around the circumference of the column.
Note 3 to entry: Whiskers are not to be confused with dendrites, which are fern-like growths on the surface of a
material, which can be formed as a result of electro(chemical)-migration of an ionic species or produced during
solidification.
Note 4 to entry: Whiskers are not to be confused with slivers as generated by mechanical metal processing.
Whiskers are not to be confused with tubular SnO structures, which may develop under damp-heat test conditions.
These structures are hollow and are typically lacking striations occurring on Sn whiskers.
3.2
termination
solderable element of a component consisting of the following elements
– base material;
– underlayer (or underlayer system, if more than one underlayer is present), if any, located
under the final plating;
– final tin or tin alloy finish
___________
Withdrawn publication.
– 8 – IEC 60068-2-82:2019 © IEC 2019
SEE: Figure 1
a) Gull wing termination b) Chip termination
Key
a base material
b underlayer (or underlayer system, if more than one underlayer is present), if any, located under the final plating
c final tin or tin alloy finish
Figure 1 – Cross-sectional views of component termination surface finishes
3.3
ΔCTE
CTE mismatch
coefficient of thermal expansion mismatch
coefficient calculated by taking the absolute after subtracting the CTE of the base material
from the CTE of the surface finish layer:
∆CTE = | CTE − CTE |
finish base material
Note 1 to entry: No underlayer system (e.g. Ni, Cu) has any influence on the CTE mismatch.
3.4
mechanical load
load related to the intended mounting/assembly condition of a particular specimen (e.g. press-
fit application: stress exerted by the plated through-hole on the press-fit pin), or as a
transitional load related to a mechanical process in a trim and form operation to adapt the
shape of the specimen to the intended use condition (e.g. bending of a connector pin)
Note 1 to entry: Mechanical load in the context of these test methods is not related to external factors, e.g.
thermo-mechanical loads arising from the mismatch of the coefficients of thermal expansion of the various
constituents of a particular test specimen upon temperature change.
3.5
classification
3.5.1
level A
consumer products, some computer and computer peripherals,
and hardware suitable for applications where the major requirement is function of the
completed assembly
3.5.2
level B
communications equipment, sophisticated business
machines, and instruments where high performance and extended life is required, and for
which uninterrupted service is desired but not mandatory
Note 1 to entry: Typically, the end-use environment would not cause failures.
IEC 60068-2-82:2019 © IEC 2019 – 9 –
3.5.3
level C
equipment where continued performance or
performance-on-demand is mandatory; equipment downtime cannot be tolerated, end-use
environment may be uncommonly harsh, and the equipment shall function when required,
such as life support systems and other critical systems
Note 1 to entry: The classification of levels A, B and C is based on IEC 61191-1.
4 Test equipment
4.1 General
The test equipment shall comprise the following elements.
4.2 Desiccator
The desiccator shall be capable of providing the conditions of temperature and humidity
specified in 6.2 and 6.5.
4.3 Humidity chamber
The humidity chamber shall meet all the requirements of IEC 60068-2-78 and be capable of
providing the conditions specified in 6.3.
4.4 Thermal cycling chamber
The thermal cycling chamber shall meet all the requirements of IEC 60068-2-14, test Na and
be capable of providing the conditions specified in 6.4.
4.5 Equipment for visual inspection
4.5.1 Scanning electron microscope
A scanning electron microscope (SEM) capable of investigating the surface of the specimen,
preferably equipped with a handling system capable of tilting and rotating the specimen, is the
preferred method of investigation owing to its high depth of focus.
4.5.2 Optical microscope/Confocal laser microscope
If not otherwise specified by the relevant specification, an optical microscope shall meet the
following requirements:
– A stereo light microscope capable of using a magnification of at least 50 × (but variable
magnification can be required for investigating different features) should be used for
surveying the specimens.
– An optical microscope allowing at least magnifications of 200 × should be used for
measuring whisker lengths. Illumination and/or specimen stage should be capable of
illuminating whiskers from different directions (e.g. use of ring lights, flexible light-guides
or rotatable fixing jigs).
– Availability of a wide range of working distances to achieve multiple focal planes.
– A suitable confocal laser microscope may also be employed.
4.6 Fixing jig
The jigs used for inspecting specimens in the optical microscope and the SEM shall meet the
following requirements:
– the jig shall be capable of tilting in every direction, up to a tilt angle of 45°;
– 10 – IEC 60068-2-82:2019 © IEC 2019
– parts shall be firmly attached on the fixture when the jig is tilted.
Care shall be taken to avoid whiskers breaking off while attaching the specimen to, and
handling the specimen with, the fixture jig.
5 Preparation for test
5.1 Selection of relevant tests
5.1.1 General
The samples shall represent finished (final) products as supplied to the customer (including
sub-process steps like trim and form, brushing, post-plating). The appropriate test methods
shall be selected according to the decision tree given in Figure 2.
IEC 60068-2-82:2019 © IEC 2019 – 11 –
Figure 2 – Selection of test methods
5.1.2 Storage conditions prior to testing
The specimen shall be kept for at least 2 h in the standard atmospheric conditions defined by
IEC 60068-1:2013, 4.3 prior to any preconditioning or test.
– 12 – IEC 60068-2-82:2019 © IEC 2019
5.1.3 Pre-aging (storage in the supply chain) before testing
Different manufacturing processes and different manufacturing routes require adapted pre-
aging times. The storage time prior to submitting specimens to preconditioning and testing
shall be at least 30 days, but not longer than 120 days after tin (alloy) plating.
5.2 Handling of the specimens
It is recommended that specimens be handled with a fixing jig as specified in 4.6 to prevent
contamination. Wherever possible, the fixing jig should not make contact with the metallic
surfaces of the specimens. However, contamination inherent to the production process and
the pre-conditioning shall not be removed (e.g. residues from plating or soldering, such as
flux residues).
The specimens shall be handled carefully to prevent whiskers from breaking off unexpectedly.
For required intermediate results reporting, already identified and broken whiskers (e.g. by
handling) shall be recorded in the final report (see Clause 10).
5.3 Sample size
The following minimum sample size shall be adopted for each test condition and for each kind
of preconditioning, unless other sample sizes are prescribed by the relevant specification.
Sample sizes for tests:
• All pins from 40 components with pin count per component < 4 pins.
• All pins from 20 components with pin count per component ≥ 4 pins and < 20 pins.
• All pins from 10 components with pin count per component ≥ 20 pins and < 40 pins.
• All pins from 5 components with pin count per component ≥ 40 pins, but not more than 400
pins.
• For mechanical parts like ESD protection shields, mechanical fixtures: ≥ 10 parts, up to an
area of 25 cm .
• For press-fit applications: ≥ 200 single pins.
• For all other parts like jumpers, wires, parts for electrical connections, male multipoint
connectors: ≥ 80 parts.
• For strip/belt galvanic: 25 cm or minimum 30 cm taken from the start and the end of the
coil.
The sample size applies to specimens with or without heat treatment in accordance with 5.5
and 5.6 and to each test condition selected from 5.1.
Similarity rules as given in 7.2 may be employed for the selection of samples.
5.4 Surface and base materials for test selection
Table 1 summarizes material systems recognized for their effective whisker mitigation, for
which certain test conditions may be omitted (see Figure 2 and Annex D). The technical
background for the omission of certain test conditions is briefly discussed in Annex D.
Table 1 applies to:
– copper-based base materials;
– ceramic-based materials;
– Fe and FeNi alloy base materials;
IEC 60068-2-82:2019 © IEC 2019 – 13 –
– other base materials which are covered with by a continuous Cu underlayer (those shall
be treated as 'Cu alloy' in Table 1), with the exception of CuZn alloys. If a CuZn alloy is
used, an Ni underlayer (0,5 µm to 4 µm) not exhibiting voids or cracks is required.
Table 1 – Material systems recognized for effective whisker mitigation
Part Sn finish layer Top Base Post-treatment
d
underlayer material
c
Galvanic Ni
Cu alloy
0,5 µm to
4 µm
Minimum No post-
3 µm Sn treatment
c
Ceramic, Fe
Galvanic Ni
2 µm to and FeNi
15 µm alloy
Galvanic matt
Reflow process
Cu alloy
a
Minimum
(Carbon content in the
Ceramic, Fe
3 µm Sn
No post-
Electronic
finish < 150 parts per
and FeNi
treatment
components
million in weight. Target
alloy
value, measured minimum
Solder area of
2 µm below the surface).
b
Cu alloy
electro- Annealing
mechanic
components Ceramic, Fe
No post-
Minimum
such as and FeNi
treatment
7 µm Sn
connectors, alloy
shieldings, etc.
c
No post-
Galvanic Ni
Cu alloy
treatment
1 µm to 3 µm
Cu alloy
Ceramic, Fe
Hot dip plating of Minimum No post-
and FeNi
Sn/SnAg/SnAgCu/SnCu0,7 3 µm Sn treatment
alloy
c
Galvanic Ni
Cu alloy
1 µm to 3 µm
Other Sn alloys not covered by Table 1 may be used, but for these alloys, the ambient test cannot be omitted.
Concerning the effectiveness of whisker mitigation, the use of galvanic matt Sn alloy finishes is currently under
discussion. In particular, the following alloying elements are considered: Ag, Bi, Cu and Pb.
a
The Sn finish shall melt during the reflow process (e.g. > 10 s at 235 °C), without exhibiting discoloration or
de-wetting.
b
Annealing shall take place within 24 h after plating for at least one hour at a temperature of 150 °C or
comparable conditions (e.g. 10 min at a temperature of 180 °C).
c
Ni-layer shall not exhibit voids or cracks (ductile Ni).
d
The post-treatment shall establish a homogeneous layer of Cu Sn and/or Cu Sn with a thickness of at least
6 5 3
0,5 µm.
The temperature-cycling test of 6.4 may be omitted if the CTE mismatch (∆CTE) (see 3.3) is
−6
less than 8 × 10 /K. The test conditions and the selection of test methods do not depend on
the presence of any underlayer system (e.g. Ni, Cu).
5.5 Preconditioning of test specimen not intended for soldering/welding
5.5.1 Preconditioning of test specimen intended for press-fit applications
Unless otherwise specified by the relevant specification, press-fit pins shall be inserted into a
plated through-hole of a laminated circuit board consisting of copper-clad epoxy woven
E-glass (for example, in accordance with IEC 61249-2-7, IEC 61249-2-35 or IEC 61249-2-22)
with the appropriate thickness and nominal finished hole diameter.
– 14 – IEC 60068-2-82:2019 © IEC 2019
The circuit board shall be pre-conditioned by subjecting it to two reflow temperature cycles in
accordance with IEC 60068-2-58 before insertion of the pins. After pin insertion, the sample
shall be stored under ambient conditions. No further thermal treatment at elevated
temperatures shall be performed.
5.5.2 Preconditioning of test specimen intended for mechanical loads other than
press fit
This preconditioning shall be applied to components like electromagnetic compatibility
protection shields, punched/stamped parts, mechanical fixations, insulation displacement
connectors and further mechanical applications.
Unless otherwise specified by the relevant specification, specimens intended for mechanical
load shall be subjected to a form operation, under nominal geometrical requirements of the
intended use case. The sample size according to 5.3 shall be selected for each test condition
selected in 5.1.
Further tests, if required, shall be described in the relevant detail specification.
5.6 Preconditioning of test specimen intended for soldering/welding
5.6.1 General
All parts intended for soldering/welding shall be subjected to a heat pre-treatment according
to Figure 3. The sample size in accordance with 5.3 shall be selected for each test leg of
Figure 3.
Figure 3 – Flow for treatment and/or bending and heat treatment
5.6.2 Mechanical pretreatment
For parts intended for soldering and additional mechanical load during production
(e.g. stitching, bending, trim and form), a characteristic preconditioning is required.
Such parts shall be subjected to a mechanical load corresponding to the intended use case,
under nominal geometrical requirements pertaining to the intended use case. In cases where
components are intended to be subjected to mechanical stress after delivery to a customer
(e.g. the forming of leads), a representative preconditioning is also required.
IEC 60068-2-82:2019 © IEC 2019 – 15 –
Unless otherwise specified by the relevant specification, the terminations of each specimen
with leads shall be bent 90° to a constant inner bending radius specified as the minimum
radius in Figure 1 of IEC 61192-3:2002.
5.6.3 Heat pre-treatment
Table 2 summarizes the required preconditioning and test legs (see Figure 3) for specimens
intended for surface-mount technology (SMT), through-hole technology (THT) and welding.
Table 2 – Preconditioning conditions and test legs for components
for different assembly processes
Test leg Component designed for assembly process
Surface-mount Through-hole Welding
technology technology
With heat treatment Mounted on PCB or non- Temperature and flux in As prescribed by the
(see Figure 3) wettable surface, in accordance with relevant specification.
accordance with IEC 60068-2-20, Test Ta,
IEC 60068-2-58, Test Method 1.
Td , Method 2.
Dipping depth: minimum
4 mm, but maximum 50 %
Alternative test: about
of termination.
50 % of the surface area
of the components'
termination shall be
wetted with flux according
to Test Td , Method 1.
Without heat treatment Product as delivered Product as delivered Product as delivered
This preconditioning shall also apply to the soldering area of connectors. A whisker test of the
connecting area shall be performed in accordance with IEC 60512-16-21.
6 Test conditions
6.1 General
The selection of the required test conditions shall be done in accordance with 5.1 and with
Figure 1.
6.2 Ambient test
The conditions given in Table 3 shall be applied for the ambient test.
Table 3 – Conditions for the ambient test
Temperature (25 ± 10) °C
Relative humidity (50 ± 25) %
Duration 4 000 h
NOTE A test chamber running at (30 ± 2) °C and (60 ± 3) % relative humidity
meets these conditions and thus can be used for this
...
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