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.

Essais d'environnement - Partie 2-82: Essais - Essai Xw1: Méthodes de vérification des trichites pour les composants et les pièces utilisés dans les ensembles électroniques

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.

General Information

Status
Published
Publication Date
13-May-2019
Current Stage
PPUB - Publication issued
Completion Date
14-May-2019
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IEC 60068-2-82
Edition 2.0 2019-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Environmental testing –
Part 2-82: Tests – Test Xw1: Whisker test methods for components and parts
used in electronic assemblies
Essais d'environnement –
Partie 2-82: Essais – Essai Xw1: Méthodes de vérification des trichites
pour les composants et les pièces utilisés dans les ensembles électroniques
IEC 60068-2-82:2019-05(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
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

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 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

---------------------- Page: 4 ----------------------
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

---------------------- Page: 5 ----------------------
– 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,

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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

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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;
---------------------- Page: 6 ----------------------
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.
---------------------- Page: 7 ----------------------
– 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
---------------------- Page: 8 ----------------------
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.
---------------------- Page: 9 ----------------------
– 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.
---------------------- Page: 10 ----------------------
IEC 60068-2-82:2019 © IEC 2019 – 9 –
3.5.3
level C
...

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