Environmental testing - Part 2-82: Tests - Test XW1: Whisker test methods for electronic and electric components

IEC 60068-2-82:2007 specifies whisker tests for electric or electronic components representing the finished stage, with tin or tin-alloy finish. However, the standard does not specify tests for whiskers that may grow as a result of external mechanical stress. This test method is employed by a relevant specification (international component or application specification) with transfer of the test severities to be applied and with defined acceptance criteria. Where tests described in this standard are considered for other components, e.g. mechanical parts as used in electrical or electronic equipment, it should be ensured that the material system and whisker growth mechanisms are comparable.

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

La CEI 60068-2-82:2007 spécifie des essais de vérification de la présence de trichites pour les composants électriques ou électroniques qui représentent la phase de finition, avec un fini en étain ou en alliage d'étain. Toutefois, la norme ne spécifie aucun essai pour les trichites susceptibles de se développer du fait d'une contrainte mécanique externe. L'utilisation de la présente méthode d'essai relève d'une spécification correspondante (spécification de composants ou d'application internationale) avec transfert des sévérités d'essai à appliquer et avec des critères d'acceptation définis. Lorsqu'il est prévu d'effectuer les essais décrits dans la présente norme pour d'autres composants, par exemple les pièces mécaniques utilisées dans les équipements électriques ou électroniques, il convient de s'assurer que le matériau constitutif et les mécanismes de développement des trichites sont comparables.

Okoljsko preskušanje – 2-82. del: Preskusi - Preskus Tx: Preskusna metoda za nitke pri elektronskih in električnih komponentah (IEC 60068-2-82:2007)

General Information

Status
Withdrawn
Publication Date
21-Jun-2007
Drafting Committee
Parallel Committee
Current Stage
6060 - Document made available
Start Date
22-Jun-2007
Completion Date
22-Jun-2007

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SLOVENSKI STANDARD
SIST EN 60068-2-82:2007
01-oktober-2007
2NROMVNRSUHVNXãDQMH±GHO3UHVNXVL3UHVNXV7[3UHVNXVQDPHWRGD]D
QLWNHSULHOHNWURQVNLKLQHOHNWULþQLKNRPSRQHQWDK ,(&

Environmental testing -- Part 2-82: Tests - Test Tx: Whisker test methods for electronic

and electric components

Umgebungseinflüsse – Teil 2-82: Prüfungen – Prüfung Tx: Whisker-Prüfverfahren für

elektronische und elektrische Bauelemente

Essais d'environnement - Partie 2-82 : Essais - Essai Tx : Méthodes d'essai des trichites

("moustaches/whiskers") pour les composants électriques et électroniques
Ta slovenski standard je istoveten z: EN 60068-2-82:2007
ICS:
19.040 Preskušanje v zvezi z Environmental testing
okoljem
31.190 Sestavljeni elektronski Electronic component
elementi assemblies
SIST EN 60068-2-82:2007 en,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
EUROPEAN STANDARD
EN 60068-2-82
NORME EUROPÉENNE
June 2007
EUROPÄISCHE NORM
ICS 19.040; 31.190
English version
Environmental testing -
Part 2-82: Tests -
Test Tx: Whisker test methods for electronic
and electric components
(IEC 60068-2-82:2007)
Essais d'environnement - Umgebungseinflüsse -
Partie 2-82: Essais - Teil 2-82: Prüfungen -
Essai Tx: Méthodes d'essai Prüfung Tx: Whisker-Prüfverfahren
des trichites ("moustaches/whiskers") für elektronische
pour les composants électriques und elektrische Bauelemente
et électroniques (IEC 60068-2-82:2007)
(CEI 60068-2-82:2007)

This European Standard was approved by CENELEC on 2007-06-01. 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 Central Secretariat 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 Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the

Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,

Sweden, Switzerland and the United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2007 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 60068-2-82:2007 E
---------------------- Page: 2 ----------------------
EN 60068-2-82:2007 - 2 -
Foreword

The text of document 91/651/FDIS, future edition 1 of IEC 60068-2-82, prepared by IEC TC 91,

Electronics assembly technology, was submitted to the IEC-CENELEC parallel vote and was approved by

CENELEC as EN 60068-2-82 on 2007-06-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2008-03-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2010-06-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice

The text of the International Standard IEC 60068-2-82:2007 was approved by CENELEC as a European

Standard without any modification.

In the official version, for Bibliography, the following note has to be added for the standard indicated:

IEC 60068-3-4 NOTE Harmonized as EN 60068-3-4:2001 (not modified).
__________
---------------------- Page: 3 ----------------------
- 3 - EN 60068-2-82:2007
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application 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 When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD

applies.
Publication Year Title EN/HD Year
IEC 60068-1 1988 Environmental testing - EN 60068-1 1994
Part 1: General and guidance
2) 3)
IEC 60068-2-14 - Environmental testing - EN 60068-2-14 1999
Part 2: Tests - Test N: Change of temperature
IEC 60068-2-20 1979 Environmental testing - HD 323.2.20 S3 1988
Part 2: Tests - Test T: Soldering
IEC 60068-2-58 2004 Environmental testing - EN 60068-2-58 2004
Part 2-58: Tests - Test Td: Test methods for + corr. December 2004
solderability, resistance to dissolution of
metallization and to soldering heat of surface
mounting devices (SMD)
2) 3)
IEC 60068-2-78 - Environmental testing - EN 60068-2-78 2001
Part 2-78: Tests - Test Cab: Damp heat,
steady state
IEC 61192-3 2002 Workmanship requirements for soldered EN 61192-3 2003
electronic assemblies -
Part 3: Through-hole mount assemblies
IEC 61760-1 2006 Surface mounting technology - EN 61760-1 2006
Part 1: Standard method for the specification
of surface mounting components (SMDs)
EN 60068-1 includes corrigendum October 1988 + A1:1992 to IEC 60068-1.
Undated reference.
Valid edition at date of issue.
HD 323.2.20 S3 includes A2:1987 to IEC 60068-2-20.
---------------------- Page: 4 ----------------------
INTERNATIONAL IEC
STANDARD 60068-2-82
First edition
2007-05
Environmental testing –
Part 2-82:
Tests – Test Tx: Whisker test methods for
electronic and electric components
PRICE CODE
Commission Electrotechnique Internationale V
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue
---------------------- Page: 5 ----------------------
– 2 – 60068-2-82 © IEC:2007(E)
CONTENTS

FOREWORD...........................................................................................................................4

1 Scope...............................................................................................................................6

2 Normative references .......................................................................................................6

3 Terms and definitions .......................................................................................................6

4 Test equipment.................................................................................................................7

4.1 Desiccator ...............................................................................................................7

4.2 Humidity chamber ...................................................................................................7

4.3 Thermal cycling chamber.........................................................................................7

4.4 Optical microscope..................................................................................................7

4.5 Scanning electron microscope microscopy ..............................................................7

4.6 Fixing jig .................................................................................................................8

5 Preparation for test...........................................................................................................8

5.1 General ...................................................................................................................8

5.2 Selection of test methods ........................................................................................8

5.3 Storage conditions prior to testing ...........................................................................8

5.4 Handling of the specimen ........................................................................................8

5.5 Preconditioning by heat treatment ...........................................................................8

5.6 Specimen preparation by leads forming...................................................................9

6 Test condition.................................................................................................................10

6.1 Ambient test ..........................................................................................................10

6.2 Damp heat test......................................................................................................10

6.3 Temperature cycling test .......................................................................................10

7 Test schedule.................................................................................................................11

7.1 Procedure for test method selection ......................................................................11

7.2 Initial measurement ...............................................................................................12

7.3 Test.......................................................................................................................12

7.4 Recovery...............................................................................................................12

7.5 Intermediate or final assessment ...........................................................................12

8 Information to be given in the relevant specification .......................................................12

9 Minimum requirements for a test report ..........................................................................13

Annex A (normative) Measurement of the whisker length .....................................................14

Annex B (informative) Examples of whiskers........................................................................15

Annex C (informative) Guidance on the sample lots and test schedules ...............................17

Annex D (informative) Guidance on acceptance criteria .......................................................19

Annex E (informative) Background on whisker growth..........................................................21

Annex F (informative) Background on ambient test ..............................................................22

Annex G (informative) Background on damp heat test..........................................................24

Annex H (informative) Background on temperature cycling test............................................27

Bibliography..........................................................................................................................32

---------------------- Page: 6 ----------------------
60068-2-82 © IEC:2007(E) – 3 –

Figure A.1 – Definition of the whisker length .........................................................................14

Figure B.1 – Nodule..............................................................................................................15

Figure B.2 – Column whisker ................................................................................................15

Figure B.3 – Filament whisker...............................................................................................15

Figure B.4 – Kinked whisker .................................................................................................16

Figure B.5 – Spiral whisker ...................................................................................................16

Figure D.1 – Smallest distance of components and circuit boards .........................................19

Figure F.1 – Whisker growth of tin plating in ambient test condition ......................................23

Figure G.1 – Growth of the oxide layer in damp heat conditions............................................25

Figure G.2a – Growth of whiskers in damp heat conditions ...................................................25

Figure G.2b – Growth of whiskers in damp heat conditions ...................................................26

Figure G.2 – Growth of whiskers...........................................................................................26

Figure H.1 – Distribution of whisker length grown on FeNi (Alloy42) base material................28

Figure H.2 – Whisker grown on FeNi (Alloy42) base material................................................29

Figure H.3 – Relationship of Δϑ and number of cycles for whisker growth on FeNi

(Alloy 42) base material ........................................................................................................29

Figure H.4 – Whisker growth on Cu based leadframes (QFP) in temperature cycling

tests .....................................................................................................................................31

Table 1 – Methods of preconditioning: Soldering simulation ....................................................

Table 2 – Methods of preconditioning: Soldering.....................................................................9

Table 3 – Severities of the ambient test ................................................................................10

Table 4 – Severities of the temperature cycling test: temperature .........................................10

Table 5 – Severities of the temperature cycling test: cycles ..................................................11

Table 6 – Suitability of test methods for different plating situations .......................................11

Table H.1 – Example for a relationship between realistic application conditions and

test conditions ......................................................................................................................30

---------------------- Page: 7 ----------------------
– 4 – 60068-2-82 © IEC:2007(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ENVIRONMENTAL TESTING –
Part 2–82: Tests – Test Tx: Whisker test methods
for electronic and electric components
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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with an IEC Publication.

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.
The text of this standard is based on the following documents:
FDIS Report on voting
91/651/FDIS 91/685/RVD

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

---------------------- Page: 8 ----------------------
60068-2-82 © IEC:2007(E) – 5 –

A list of all parts in the IEC 60068 series, under the general title Environmental testing, can be

found on the IEC website.

The committee has decided that the contents of this publication will remain unchanged until

the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in

the data related to the specific publication. At this date, the publication will be

• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.
---------------------- Page: 9 ----------------------
– 6 – 60068-2-82 © IEC:2007(E)
ENVIRONMENTAL TESTING –
Part 2–82: Tests – Test Tx: Whisker test methods
for electronic and electric components
1 Scope

This part of IEC 60068 specifies whisker tests for electric or electronic components

representing the finished stage, with tin or tin-alloy finish. However, the standard does not

specify tests for whiskers that may grow as a result of external mechanical stress.

This test method is employed by a relevant specification (international component or

application specification) with transfer of the test severities to be applied and with defined

acceptance criteria.

Where tests described in this standard are considered for other components, e.g. mechanical

parts as used in electrical or electronic equipment, it should be ensured that the material

system and whisker growth mechanisms are comparable.
2 Normative references

The following referenced documents are indispensable for the application 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 60068-1:1988, Environmental testing – Part 1: General and guidance

IEC 60068-2-14, Environmental testing – Part 2-14: Tests – Test N: Change of temperature

IEC 60068-2-20:1979, Environmental testing – Part 2-20: Tests – Test T: Soldering

IEC 60068-2-58:2004, 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 60068-2-78, Environmental testing – Part 2-78: Test Cab: Damp heat, steady state

IEC 61192-3:2002, Workmanship requirements for soldered electronic assemblies – Part 3:

Through-hole mount assemblies
IEC 61760-1:2006, Surface mounting technology – Part 1: Standard method for the
specification of surface mounting components (SMDs)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60068-1, as well as

the following, apply.
3.1
whisker
metallic protrusion which spontaneously grows during storage or use
---------------------- Page: 10 ----------------------
60068-2-82 © IEC:2007(E) – 7 –

NOTE 1 Whiskers typically do not require any electrical field for their growth and may not be mixed with products

of electrochemical migration. Typical signs of whiskers include:
– striations in growth direction;
– typically no branching;
– typically constant diameters.
Exceptions are known, but rare and may require detailed investigation.
For the purposes of this standard, 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 For the purposes of this standard, whiskers have the following characteristics:

– 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 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-migration of an ionic species or produced during solidification.

3.2
material system
termination consists of the following elements:
a) base material;
b) underlayer, if any, located under the final plating;
c) final tin or tin alloy plating.

NOTE There may be additional layers between the base material and the underlayer. The penultimate layer is the

used bulk material or the deposited layer underneath the final tin or tin alloy plating of the component.

4 Test equipment
The test equipment shall comprise the following elements:
4.1 Desiccator

The desiccator shall be capable of providing the conditions of temperature and humidity

specified in 6.1.
4.2 Humidity chamber

The humidity chamber shall meet all the requirements of IEC 60068-2-78 and be capable of

providing the conditions specified in 6.2.
4.3 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 6.3.
4.4 Optical microscope

An optical stereo-microscope with a magnification of at least 50 times and an appropriate

illumination, capable of detecting whiskers with a length of 10 μm.

If used for measurement, the microscope shall be equipped with a scale or electronic

detection system capable for length measurement with an accuracy of at least ±5 µm.

4.5 Scanning electron microscope

A scanning electron microscope (SEM) capable of investigating the surface of the specimen,

preferably equipped with a handling system capable to tilt and rotate the specimen.

---------------------- Page: 11 ----------------------
– 8 – 60068-2-82 © IEC:2007(E)
4.6 Fixing jig

The fixture jig shall be capable of setting samples in any of the test chambers specified in 4.1,

4.2 and 4.3 without affecting compliance with the specified requirements.

The jig should also be attachable to the optical microscope or be appropriately small in size

so that it can be inserted in the SEM sample chamber.
5 Preparation for test
5.1 General
The samples shall represent finished products as supplied to the market.
NOTE Guidance on suitable sample sizes is provided in Annex C.
5.2 Selection of test methods

Choose the appropriate test method according to the type of final plating, underlayer and

base material of the specimen according to Table 6.
5.3 Storage conditions prior to testing

The specimen shall be kept for at least 2 h in the standard atmospheric conditions defined in

IEC 60068-1, 5.3.1 prior to any preconditioning or test.
5.4 Handling of the specimen

It is recommended to hold the specimen with a fixture jig as specified in 4.6 to prevent them

from being contaminated unexpectedly. The fixture jig shall not contact the metallic surfaces

of the specimen to be tested. The sample shall be handled carefully to prevent the grown

whiskers from falling away unexpectedly. Broken whiskers shall be recorded, see 7.4.

Where there is a possibility of grown whiskers to drop down, an appropriate fixture jig design

shall be considered in advance of the test. Conductive sputter coating typically used to aid

SEM inspection, such as C, Pt, or Au, shall not be deposited on the specimen.
5.5 Preconditioning by heat treatment
5.5.1 Soldering simulation prior to ambient and damp heat test (see 6.1 and 6.2)
a) Components intended for soldering

Before soldering simulation, the specimen of material descriptions case 1.1, case 3 or case 4

shall have been stored under room temperature for more than 30 days after the last

manufacturing process, e.g. as indicated by the date code of the product.

Unless otherwise specified by the relevant specification, the components shall be submitted to

a soldering simulation according to Table 1 without the use of solder and without contact to

any metal surface.
---------------------- Page: 12 ----------------------
60068-2-82 © IEC:2007(E) – 9 –
Table 1 – Methods of preconditioning – Soldering simulation
Soldering simulation
Component type
First half of the sample Second half of the sample
SMD Reflow heat treatment None
according to Table 3 (Group 3) of
8.1.2.1, IEC 60068-2-58
Other Bath with inert liquid None
according to test Ta, method 1 of
IEC 60068-2-20
Dipping depth: max. 4 mm.
e.g. Perfluoropolyether PFPE.
After preconditioning the test shall be started within 168 h.
Conditions of thermal preconditioning shall be recorded.
b) Components not intended for soldering
No thermal preconditioning shall be applied.
5.5.2 Soldering simulation prior to temperature cycling test (see 6.3)
a) Components intended for soldering

Before soldering, the specimen of material descriptions case 1.1, case 3 or case 4 shall have

been stored under room temperature for more than 30 days after the last manufacturing

process, e.g. as indicated by the date code of the product.

Unless otherwise specified by the relevant specification, the components may be assembled

onto printed circuit boards. The circuit board material shall be epoxide woven glass with a

thickness of (1,6 ± 0,2) mm. The assembly process shall be according to Table 2.
Table 2 – Methods of preconditioning – Soldering
Component type Soldering
SMD Hot air convection reflow soldering with SnAgCu solder , low activity flux,
according to Table 3 (Group 3) of 8.1.2.1, IEC 60068-2-58

Other Wave soldering by use of a soldering profile according to 6.1 of IEC 61760-

1, using SnAgCu solder

Apply 50 % of the solder paste volume recommended for typical production. This requirement shall ensure that

after soldering a part of the terminal surface is not covered by solder and remains for inspection.

After this preconditioning the test shall be started within 168 h.
The soldering conditions shall be recorded.
b) Components not intended for soldering

Unless otherwise described by the relevant specification, the components are tested in

unassembled stage.
5.6 Specimen preparation by leads forming

In cases where components are subjected to mechanical stress after delivery, e.g. the

forming of leads, a representative pre-conditioning is required. Unless otherwise specified by

the relevant specification, each specimen shall be bent 90° to the consistent inner bending

radius specified as the minimum radius in Table 1, of IEC 61192-3.
---------------------- Page: 13 ----------------------
– 10 – 60068-2-82 © IEC:2007(E)
6 Test conditions
6.1 Ambient test

Unless otherwise specified by the relevant specification, apply the conditions according to

Table 3 and in accordance with the severity selected from Table 6:
Table 3 – Severities of the ambient test
Temperature Relative humidity
Severity
°C %
A 30 ± 2 60 ± 3
B 25 ± 10 50 ± 25
Test duration: 4 000 h.
6.2 Damp heat test

Unless otherwise specified by the relevant specification, use the humidity chamber specified

in IEC 60068-2-78 and apply the conditions stated below:
− temperature: (55 ± 3) °C
− relative humidity: (85 ± 5) %
− test duration: 2 000 h.

Apply heating, cooling, moistening, and dehumidifying in the test in a way that dew does not

condensate on the specimens.
6.3 Temperature cycling test

Unless otherwise specified by the relevant specification, apply the procedures specified in

IEC 60068-2-14, test Na with the conditions stated below:

For the lower temperature and upper temperature, one severity according to Table 4 shall be

used.
Table 4 – Severities of the temperature cycling test – Temperature
Severity Lower temperature Upper temperature
(First character) °C °C
K -40 ± 5 85 ± 2
L -55 ± 5 85 ± 2
M -40 ± 5 125 ± 2
N -55 ± 5 125 ± 2
NOTE Neither the sequence of listed severities nor the range between lower and
upper temperature impose a specific degree of
...

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