IEC 61051-1:2018

Varistors for use in electronic equipment - Part 1: Generic specification

IEC 61051-1:2018 is a generic specification and is applicable to varistors with symmetrical voltage-current characteristics for use in electronic equipment. It establishes standard terms, inspection procedures and methods of test for use in sectional and detail specifications for quality assessment or any other purpose. This edition includes the following significant technical changes with respect to the previous edition:
a) 10 new terms and definitions – leaded varistors, surface mount varistors(SMV), electrostatic discharge (ESD), ESD clamping voltage, equivalent rectangular pulse duration, maximum peak current derating characteristic, rated average dissipation power, rated energy, abnormal overvoltage withstanding duration and temperature derating curve – have been added (see 3.6, 3.7, 3.14, 3.15, 3.19, 3.20, 3.23, 3.24, 3.25 and 3.29);
b) General requirements for electrical tests and 7 new test items – clamping voltage, ESD clamping voltage, maximum peak current, rated average dissipation power, rated energy, electrostatic discharge (ESD), robustness of terminations of surface mount varistors – have been added (see 6.5, 6.11, 6.12, 6.13, 6.14, 6.15, 6.16 and 6.17.8);
c) In 6.6, 6.7, 6.8, 6.9.3, 6.23.2, 6.23.4 and 6.26, following test items have been revised:
- Varistor voltage, leakage current and capacitance: more detailed requirements and information have been added;
- Voltage proof – foil method: the space between the edge of the foil and each termination has been changed from 1 mm ~ 1,5 mm to 3 mm ~ 3.5 mm for testing varistors not having axial terminations and the minimum space between the foil and the termination has been changed from 1 mm to 3 mm for testing varistors having axial terminations;
- Climatic sequence – dry heat: the method has been changed from Ba to Bb;
- Climatic sequence – cold: the method has been changed from Aa to Ab;
- Endurance at upper category temperature: the method of “applying test voltages in cycles of 1,5 h on and 0,5 h off” has been changed to the method of applying test voltages continuously throughout the test lasting for 1 000 h;
d) The test items of pulse current, voltage under pulse condition and bump have been deleted from the section of test and measurement procedures;
e) Annex A and the contents referring to the test fixture specified in Annex A have been deleted;
f) All contents related to silicon carbide varistors have been deleted;
g) A new normative annex entitled “Test pulses used in this specification” (Annex B) has been added;
h) A new informative annex entitled "Recommended measurement/test methods for characteristics and parameters for application reference" (Annex C) has been added, in which guidelines of measuring/testing characteristics and parameters for application reference including voltage vs. current characteristic, maximum peak current derating characteristic, thermal resistance and abnormal overvoltage withstanding duration have been given.

Varistances utilisées dans les équipements électroniques - Partie 1: Spécification générique

L'IEC 61051-1:2018 est une spécification générique applicable aux varistances à caractéristiques tension-courant symétriques, utilisées dans les équipements électroniques. Elle établit les termes normalisés, les procédures de contrôle et les procédures d'essai utilisés dans les spécifications intermédiaires et particulières à des fins d'assurance de la qualité ou à toute autre fin. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) 10 nouveaux termes et définitions (varistances à fils, varistances montées en surface (VMS), décharge électrostatique (DES), tension d'écrêtage de DES, durée d'impulsion rectangulaire équivalente, caractéristique de réduction du courant maximal de crête, puissance de dissipation moyenne assignée, énergie assignée, durée de résistance à une surtension anormale et courbe de réduction de la température) ont été ajoutés (voir 3.6, 3.7, 3.14, 3.15, 3.19, 3.20, 3.23, 3.24, 3.25 et 3.29);
b) des exigences générales pour les essais électriques et 7 nouveaux essais (tension d'écrêtage, tension d'écrêtage de DES, courant maximal de crête, puissance de dissipation moyenne assignée, énergie assignée, décharge électrostatique (DES), robustesse des sorties des varistances montées en surface) ont été ajoutés (voir 6.5, 6.11, 6.12, 6.13, 6.14, 6.15, 6.16 et 6.17.8);
c) en 6.6, 6.7, 6.8, 6.9.3, 6.23.2, 6.23.4 et 6.26, les essais suivants ont été révisés:
- Tension de la varistance, courant de fuite et capacité: des exigences et des informations plus détaillées ont été ajoutées;
- Tenue en tension – méthode de la feuille métallique: l'espace entre le bord de la feuille et chaque sortie a été modifié de 1 mm ~ 1,5 mm à 3 mm ~ 3,5 mm pour soumettre à l'essai les varistances qui ne possèdent aucune sortie axiale et l'espace minimal entre le bord de la feuille et la sortie a été modifié de 1 mm à 3 mm pour soumettre à l'essai les varistances qui possèdent des sorties axiales;
- Séquence climatique – chaleur sèche: la méthode a été modifiée (Ba en Bb);
- Séquence climatique – froid: la méthode a été modifiée (Aa en Ab);
- Endurance à la température maximale de catégorie: la méthode consistant à "appliquer des tensions d'essai par cycles de 1,5 h d'application et de 0,5 h de repos" a été modifiée au profit de la méthode consistant à appliquer des tensions d'essai en continu tout au long de l'essai qui dure 1 000 h;
d) les essais de courant d'impulsion, de tension en condition d'impulsion et de secousses ont été supprimés de l'article concernant les procédures d'essai et de mesure;
e) l'Annexe A et les contenus qui font référence aux appareils de montage d'essai spécifiés à l'Annexe A ont été supprimés;
f) tous les contenus concernant les varistances au carbure de silicium ont été supprimés;
g) une nouvelle annexe normative intitulée "Impulsions d'essai utilisées dans la présente spécification" (Annexe B) a été ajoutée;
h) une nouvelle annexe informative intitulée "Méthodes de mesure/d'essai recommandées pour les caractéristiques et paramètres pour référence d'application" (Annexe C) a été ajoutée; elle donne des lignes directrices pour les caractéristiques et paramètres de mesure/d'essai et pour référence d'application (notamment la caractéristique tension-courant, la caractéristique de réduction du courant maximal de crête, la résistance thermique et la durée de résistance à une surtension anormale).

General Information

• Status: Published
• Publication Date: 28-Oct-2018
• ICS: 31.020 - Electronic components in general
• ICS: 31.040.99 - Other resistors
• ICS: 31.240 - Mechanical structures for electronic equipment
• Technical Committee: TC 40 - Capacitors and resistors for electronic equipment
• Drafting Committee: MT 61051-1 - TC 40/MT 61051-1
• Current Stage: PPUB - Publication issued
• Start Date: 29-Oct-2018
• Completion Date: 05-Oct-2018

Relations

• Revises: IEC 61051-1:2007 - Varistors for use in electronic equipment - Part 1: Generic specification
• Effective Date: 05-Sep-2023

Overview

IEC 61051-1:2018 is the third edition generic specification for varistors with symmetrical voltage‑current characteristics used in electronic equipment. The standard defines terms, inspection procedures and test methods for use in sectional and detail specifications - supporting quality assessment, product qualification and application‑oriented measurement. This edition updates definitions and test requirements to cover leaded and surface mount varistors (SMV), electrostatic discharge (ESD) behaviour, energy/dissipation ratings and revised test procedures.

Key technical topics and requirements

• Scope: Generic specification for varistors for electronic equipment; applies to symmetrical V–I varistors.
• New and revised definitions: 10 new terms added (e.g., leaded varistors, SMV, ESD clamping voltage, rated energy, temperature derating curve).
• Electrical test coverage: Expanded general requirements and seven new test items including:
  • Clamping voltage and ESD clamping voltage
  • Maximum peak current and maximum peak current derating characteristic
  • Rated average dissipation power and rated energy
  • Electrostatic discharge (ESD) testing for SMV
  • Robustness of terminations for surface mount varistors
• Revised measurements: More detailed requirements for varistor voltage, leakage current and capacitance.
• Test method updates: Changes to voltage‑proof (foil spacing), climatic sequence procedures, and endurance testing (continuous voltage application for 1 000 h).
• Deleted content: Pulse current/voltage under pulse/bump tests, Annex A test fixture, and all silicon carbide varistor content removed.
• New annexes: Normative Annex B (test pulses used) and informative Annex C (recommended measurement/test methods and application reference: V–I curves, derating, thermal resistance, abnormal overvoltage duration).

Practical applications

• Ensures consistent surge protection and transient suppression performance by standardizing test methods and rated parameters.
• Helps designers choose varistors for ESD protection, transient suppression in consumer electronics, telecommunications, industrial control and other electronic systems.
• Enables manufacturers and test laboratories to qualify products, verify clamping behaviour, energy handling and long‑term reliability under climatic and electrical stress.

Who uses IEC 61051-1:2018

• Component manufacturers (qualification and product specifications)
• Test laboratories and QA teams (type and lot testing, conformity)
• Electronic design engineers (selecting varistors by V–I, energy and ESD specs)
• Procurement and regulatory compliance professionals producing or sourcing varistor devices

Related standards

Refer to sectional/detail specifications and other parts of the IEC 61051 series and applicable EMC/ESD standards for system‑level requirements and complementary test methods.

Standards Content (Sample)

IEC 61051-1 ®
Edition 3.0 2018-10
REDLINE VERSION
INTERNATIONAL
STANDARD
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Varistors for use in electronic equipment –
Part 1: Generic specification
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IEC 61051-1 ®
Edition 3.0 2018-10
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Varistors for use in electronic equipment –

Part 1: Generic specification
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.040.99 ISBN 978-2-8322-6211-5

– 2 – IEC 61051-1:2018 RLV © IEC 2018
CONTENTS
FOREWORD . 7
1 Scope . 10
2 Normative references . 10
3 Terms and definitions . 12
4 Technical data . 19
4.1 Units, symbols and terminology . 19
4.2 Preferred values and characteristics . 19
4.3 Marking . 19
4.3.1 General . 19
4.3.2 Coding . 19
5 Quality assessment procedures . 20
5.1 General . 20
5.1.1 Overview . 20
5.1.2 Applicability of qualification approval . 20
5.1.3 Applicability of capability approval . 20
5.1.4 Applicability of technology approval . 21
5.2 Primary stage of manufacture . 21
5.3 Subcontracting . 21
5.4 Structurally similar components . 21
5.5 Qualification approval procedures . 22
5.5.1 Eligibility for qualification approval . 22
5.5.2 Application for qualification approval . 22
5.5.3 Test procedure for qualification approval . 22
5.5.4 Granting of qualification approval . 22
5.5.5 Maintenance of qualification approval . 22
5.5.6 Quality conformance inspection . 22
5.6 Capability approval procedures . 23
5.6.1 General . 23
5.6.2 Eligibility for capability approval . 23
5.6.3 Application for capability approval . 23
5.6.4 Description of capability . 24
5.6.5 Demonstration and verification of capability . 24
5.6.6 Programme for capability approval . 25
5.6.7 Capability approval test report . 25
5.6.8 Abstract of description of capability . 25
5.6.9 Modifications likely to affect the capability approval . 25
5.6.10 Initial capability approval . 26
5.6.11 Granting of capability approval . 27
5.6.12 Maintenance of capability approval . 27
5.6.13 Extension of capability approval . 27
5.6.14 Quality conformance inspection . 27
5.7 Rework and repair. 28
5.7.1 Rework . 28
5.7.2 Repair . 28
5.8 Release for delivery . 28
5.8.1 General . 28

5.8.2 Certified records of released lots . 28
5.8.3 Delayed delivery . 28
5.8.4 Release for delivery before the completion of Group B tests . 29
5.9 Alternative test methods . 29
5.10 Unchecked parameters . 29
5.11 Characteristics and parameters for application reference . 29
5.12 Technology approval procedures . 29
5.12.1 General . 29
5.12.2 Eligibility for technology approval . 29
5.12.3 Application of technology approval . 30
5.12.4 Description of technology . 30
5.12.5 Demonstration and verification of the technology . 30
5.12.6 Granting of technology approval . 30
5.12.7 Maintenance of technology approval . 30
5.12.8 Quality conformance inspection . 30
5.12.9 Failure rate level determination. 30
5.12.10 Outgoing quality level . 30
6 Test and measurement procedures . 30
6.1 General . 30
6.2 Standard atmospheric conditions . 31
6.2.1 Standard atmospheric conditions for testing . 31
6.2.2 Recovery conditions . 31
6.2.3 Referee conditions . 31
6.2.4 Reference conditions . 31
6.3 Drying and recovery . 32
6.3.1 General . 32
6.3.2 Procedure I . 32
6.3.3 Procedure II . 32
6.4 Visual examination and check of dimensions . 32
6.4.1 Visual examination . 32
6.4.2 Marking . 32
6.4.3 Dimensions (gauging) . 32
6.4.4 Dimensions (detail) . 32
Nominal varistor voltage or leakage current (not applicable to pulse
measurements) .
Test procedure .
Measurement and requirements .
Pulse current .
Standard pulse currents .
Tolerances .
Measurement of the pulse current .
4.7 Voltage under pulse condition .
4.8 Capacitance .
6.5 General requirements for electrical tests . 34
6.6 Varistor voltage . 35
6.7 Leakage current . 36
6.8 Capacitance . 36
6.9 Voltage proof (for insulated varistors only) . 36
6.9.1 General . 36

– 4 – IEC 61051-1:2018 RLV © IEC 2018
6.9.2 V-block method . 36
6.9.3 Metal ball method . 37
6.9.4 Foil method . 37
6.10 Insulation resistance (for insulated varistors only) . 37
6.10.1 Test procedure . 37
6.10.2 Measurement and requirements . 37
6.11 Clamping voltage . 38
6.12 ESD clamping voltage (for surface mount electrostatic protective varistors
only) . 38
6.13 Maximum peak current . 38
6.13.1 Initial measurement . 38
6.13.2 Test procedure . 38
6.13.3 Final inspection, measurement and requirements . 39
6.14 Rated average dissipation power . 39
6.14.1 General . 39
6.14.2 Initial measurement . 39
6.14.3 Test procedure . 39
6.14.4 Final inspection, measurement and requirements . 40
6.15 Rated energy . 40
6.15.1 General . 40
6.15.2 Initial measurement . 40
6.15.3 Test procedure . 40
6.15.4 Final inspection, measurement and requirements . 41
6.16 Electrostatic discharge (ESD) (for surface mount electrostatic protective
varistors only) . 41
6.16.1 Initial measurement . 41
6.16.2 Test procedure . 41
6.16.3 Final inspection, measurement and requirements . 41
6.17 Robustness of terminations . 41
6.17.1 General . 41
6.17.2 Test Ua – Tensile . 42
6.17.3 Test Ub – Bending (half of the number of terminations) . 42
6.17.4 Test Uc – Torsion (the other half of the number of terminations) . 42
6.17.5 Test Ud – Torque (for terminations with threaded studs or screws and for
integral mounting devices) . 42
6.17.6 Visual examination . 43
6.17.7 Final measurement . 43
6.17.8 Robustness of terminations of surface mount varistors . 43
6.18 Resistance to soldering heat . 44
6.18.1 Preconditioning . 44
6.18.2 Test procedure . 44
6.18.3 Recovery . 44
6.18.4 Final inspection, measurement and requirements . 45
6.19 Solderability . 45
6.19.1 General . 45
6.19.2 Test procedure . 45
6.19.3 Final inspection, measurements and requirements. 45
6.20 Rapid change of temperature . 46
6.20.1 Initial measurement . 46
6.20.2 Test procedure . 46

6.20.3 Final inspection, measurement and requirements . 46
Bump .
Initial measurement .
Test procedure .
Final inspection, measurement and requirements .
6.21 Shock . 47
6.21.1 Initial measurement . 47
6.21.2 Test procedure . 47
6.21.3 Final inspection, measurement and requirements . 47
6.22 Vibration . 47
6.22.1 Initial measurement . 47
6.22.2 Test procedure . 47
6.22.3 Final inspection, measurement and requirements . 47
6.23 Climatic sequence. 48
6.23.1 General . 48
6.23.2 Initial measurement . 48
6.23.3 Dry heat . 48
6.23.4 Damp heat, cyclic, Test Db, first cycle . 48
6.23.5 Cold. 48
6.23.6 Low air pressure . 48
6.23.7 Damp heat, cyclic, Test Db, remaining cycles . 48
6.23.8 Final inspection, measurement and requirements . 49
6.24 Damp heat, steady state . 49
6.24.1 Initial measurement . 49
6.24.2 Test procedure . 49
6.24.3 Final inspection, measurement and requirements . 49
6.25 Fire hazard . 50
6.26 Endurance at upper category temperature . 50
6.26.1 Test system . 51
6.26.2 Initial measurement . 51
6.26.3 Mounting of the samples . 51
6.26.4 Test procedure, measurement and requirements . 51
6.27 Solvent resistance of marking . 52
6.27.1 Test procedure . 52
6.27.2 Requirements . 52
6.28 Component solvent resistance . 52
6.28.1 Initial measurements . 52
6.28.2 Test procedure . 52
6.28.3 Measurement and requirements . 52
6.29 Mounting (for surface mount varistors only) . 53
Annex (normative) Mounting for measurements of varistors .
Annex (normative) Interpretation of sampling plans and procedures as described in
IEC 60410 for use within the IEC quality assessment system for electronic components .
Annex A (normative informative) Rules for the preparation of detail specifications for
capacitors and resistors for electronic equipment . 55
Annex B (normative) Test pulses used in this specification . 58
B.1 Types of test pulses . 58
B.1.1 General . 58
B.1.2 Pulse type 1 . 58

– 6 – IEC 61051-1:2018 RLV © IEC 2018
B.1.3 Pulse type 2 (rectangular pulse) . 58
B.1.4 Pulse type 3 (ESD discharge pulse) . 58
B.2 Pulse parameters . 59
B.2.1 Value of the pulse current/voltage. 59
B.2.2 Virtual front time T . 59
B.2.3 Virtual origin O . 60
B.2.4 Virtual time to half-value T . 60
B.2.5 Virtual duration of peak of a rectangular pulse current T . 60
D
B.2.6 Virtual total duration T of a pulse current . 60
T
B.3 Tolerances for the pulses . 61
Annex C (informative) Recommended measurement/test methods for characteristics
and parameters for application reference . 62
C.1 Voltage vs. current characteristic . 62
C.2 Maximum peak current derating characteristic . 63
C.2.1 Rationale related to this test . 63
C.2.2 Failure criteria . 63
C.2.3 Pulse life test . 63
C.2.4 Graphing of the maximum peak current derating curves . 65
C.3 Thermal resistance (for leaded varistors only) . 65
C.3.1 Test system . 65
C.3.2 Mounting of the sample . 66
C.3.3 Test procedure . 66
C.4 Abnormal overvoltage withstanding duration . 66
C.4.1 Test system . 66
C.4.2 Test procedure . 67
C.4.3 Requirements . 67

Figure 1 – General scheme for capability approval . 23
Figure 2 – Mounting method for measurement of surface mount varistors . 53
Figure B.1 – Shape of pulse current type 1 . 58
Figure B.2 – Shape of pulse voltage type 1 . 59
Figure B.3 – Shape of pulse type 2 . 59
Figure B.4 – Shape of pulse type 3 . 60
Figure C.1 – Maximum peak current derating characteristic . 65

Table 1 – Standard atmospheric conditions . 31
Table 2 – Force for wire terminations . 42
Table 3 – Torque . 43
Table 4 – Number of cycles . 48
Table B.1 – Accepted differences between specified and recorded pulse values . 61
Table B.2 – Tolerances for pulse type 3 . 61

INTERNATIONAL ELECTROTECHNICAL COMMISSION
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VARISTORS FOR USE IN ELECTRONIC EQUIPMENT –

Part 1: Generic specification
FOREWORD
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– 8 – IEC 61051-1:2018 RLV © IEC 2018
International Standard IEC 61051-1 has been prepared by IEC technical committee 40:
Capacitors and resistors for electronic equipment.
This third edition cancels and replaces the second edition published in 2007. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) 10 new terms and definitions – leaded varistors, surface mount varistors(SMV), electrostatic
discharge (ESD), ESD clamping voltage, equivalent rectangular pulse duration, maximum
peak current derating characteristic, rated average dissipation power, rated energy,
abnormal overvoltage withstanding duration and temperature derating curve – have been
added (see 3.6, 3.7, 3.14, 3.15, 3.19, 3.20, 3.23, 3.24, 3.25 and 3.29);
b) General requirements for electrical tests and 7 new test items – clamping voltage, ESD
clamping voltage, maximum peak current, rated average dissipation power, rated energy,
electrostatic discharge (ESD), robustness of terminations of surface mount varistors – have
been added (see 6.5, 6.11, 6.12, 6.13, 6.14, 6.15, 6.16 and 6.17.8);
c) In 6.6, 6.7, 6.8, 6.9.3, 6.23.2, 6.23.4 and 6.26, following test items have been revised:
• Varistor voltage, leakage current and capacitance: more detailed requirements and
information have been added;
• Voltage proof – foil method: the space between the edge of the foil and each termination
has been changed from 1 mm ~ 1,5 mm to 3 mm ~ 3.5 mm for testing varistors not having
axial terminations and the minimum space between the foil and the termination has been
changed from 1 mm to 3 mm for testing varistors having axial terminations;
• Climatic sequence – dry heat: the method has been changed from Ba to Bb;
• Climatic sequence – cold: the method has been changed from Aa to Ab;
• Endurance at upper category temperature: the method of "applying test voltages in
cycles of 1,5 h on and 0,5 h off" has been changed to the method of applying test voltages
continuously throughout the test lasting for 1 000 h;
d) The test items of pulse current, voltage under pulse condition and bump have been deleted
from the section of test and measurement procedures;
e) Annex A and the contents referring to the test fixture specified in Annex A have been
deleted;
f) All contents related to silicon carbide varistors have been deleted;
g) A new normative annex entitled "Test pulses used in this specification" (Annex B) has been
added;
h) A new informative annex entitled "Recommended measurement/test methods for
characteristics and parameters for application reference" (Annex C) has been added, in
which guidelines of measuring/testing characteristics and parameters for application
reference including voltage vs. current characteristic, maximum peak current derating
characteristic, thermal resistance and abnormal overvoltage withstanding duration have
been given.
The text of this International Standard is based on the following documents:
FDIS Report on voting
40/2621/FDIS 40/2625/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.
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that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this publication using a colour printer.

– 10 – IEC 61051-1:2018 RLV © IEC 2018
VARISTORS FOR USE IN ELECTRONIC EQUIPMENT –

Part 1: Generic specification
1 Scope
This part of IEC 61051 is applicable to varistors with symmetrical voltage-current characteristics
for use in electronic equipment.
1.2 Object
The object of this standard is to establish standard terms, inspection procedures and methods of
test for use in sectional and detail specifications for Qualification Approval and for Quality
Assessment Systems for electronic components.
This part of IEC 61051 is a generic specification and is applicable to varistors with symmetrical
voltage-current characteristics for use in electronic equipment.
It establishes standard terms, inspection procedures and methods of test for use in sectional
and detail specifications for quality assessment or any other purpose.
NOTE Detail specifications can be specifications within the IEC system, another specification system linked to IEC,
or specified by the manufacturer or user. The drafting of a complete detail specification by IEC technical committee 40,
if required, follows the rules described in Annex A.
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 60027 (all parts), Letter symbols to be used in electrical technology
IEC 60050 (all parts), International Electrotechnical Vocabulary (IEV)
IEC 60060-2:1994, High-voltage test techniques – Part 2: Measuring systems
IEC 60062:2004, Marking codes for resistors and capacitors
IEC 60068-1:1988 2013, Environmental testing – Part 1: General and guidance
Amendment 1 (1992)
IEC 60068-2-1:2007, Environmental testing – Part 2-1: Tests – Test A: Cold
IEC 60068-2-2:1974 2007, Environmental testing – Part 2-2: Tests – Tests B: Dry heat
Amendment 1 (1993)
Amendment 2 (1994)
IEC 60068-2-6:1995 2007, Environmental testing – Part 2-6: Tests – Test Fc and guidance:
Vibration (Sinusoidal)
IEC 60068-2-13:1983, Environmental testing – Part 2-13: Tests – Test M: Low air pressure

IEC 60068-2-14:1984 2009, Environmental testing – Part 2-14: Tests – Test N: Change of
temperature
Amendment 1 (1986)
IEC 60068-2-20:1979 2008, Environmental testing – Part 2-20: Tests – Test T: Soldering
Test methods for solderability and resistance to soldering heat of devices with leads
Amendment 2 (1987)
IEC 60068-2-21:2006, Environmental testing – Part 2-21: Tests – Test U: Robustness of
terminations and integral mounting devices
IEC 60068-2-21:2006/COR1:2012
IEC 60068-2-27:1987 2008, Environmental testing – Part 2-27: Tests – Test Ea and guidance:
Shock
IEC 60068-2-29:1987, Environmental testing – Part 2: Tests – Test Eb and guidance: Bump
IEC 60068-2-30:2005, Environmental testing – Part 2-30: Tests – Test Db and guidance: Damp
heat, cyclic (12 h + 12-hour cycle)
IEC 60068-2-45:1980, Environmental testing – Part 2-45: Tests – Test XA and guidance –
Immersion in cleaning solvents
IEC 60068-2-45:1980/AMD1:1993
IEC 60068-2-54:2005, Environmental testing – Part 2-54: Tests – Test Ta: Solderability testing
of electronic components by the wetting balance method
IEC 60068-2-58:2004 2015, 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 60068-2-69:1995 2017, Environmental testing – Part 2-69: Tests – Test Te/Tc:
Solderability testing of electronic components for surface mount technology and printed boards
by the wetting balance (force measurement) method
IEC 60068-2-78:2001 2012, Environmental testing – Part 2-78: Tests – Test Cab: Damp heat,
steady state
IEC 60294:1969, Measurement of the dimensions of a cylindrical component having two axial
terminations
IEC 60410:1973, Sampling plans and procedures for inspection by attributes
IEC 60617:2007, Graphical symbols for diagrams
(available at http://std.iec.ch/iec60617)
IEC 60695-11-5:2004 2016, Fire hazard testing – Part 11-5: Test flames – Needle-flame test
method – Apparatus, confirmatory test arrangement and guidance
IEC 60717:1981 2012, Method for the determination of the space required by capacitors and
resistors with unidirectional terminations
IEC 61000-4-2:2008, Electromagnetic Compatibility (EMC) – Part 4-2: Testing and
measurement techniques – Electrostatic discharge immunity test

– 12 – IEC 61051-1:2018 RLV © IEC 2018
IEC 61193-2, Quality assessment systems – Part 2: Selection and use of sampling plans for
inspection of electronic components and packages
IEC 61249-2-7:2002, Materials for printed boards and other interconnecting structures –
Part 2-7: Reinforced base materials clad and unclad – Epoxide woven E-glass laminated sheet
of defined flammability (vertical burning test), copper-clad
IEC QC 001002-3, see http://www.iecq.org
ISO 1000:1992, SI units and recommendations for the use of their multiples and of certain other
units
Amendment 1 (1998)
ISO 80000-1:2009, Quantities and units – Part 1: General
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
type
group of components having simila
...

IEC 61051-1 ®
Edition 3.0 2018-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Varistors for use in electronic equipment –
Part 1: Generic specification
Varistances utilisées dans les équipements électroniques –
Partie 1: Spécification générique

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IEC 61051-1 ®
Edition 3.0 2018-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Varistors for use in electronic equipment –

Part 1: Generic specification
Varistances utilisées dans les équipements électroniques –

Partie 1: Spécification générique

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.040.99 ISBN 978-2-8322-6089-0

– 2 – IEC 61051-1:2018 © IEC 2018
CONTENTS
FOREWORD . 7
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 10
4 Technical data . 15
4.1 Units, symbols and terminology . 15
4.2 Preferred values and characteristics . 15
4.3 Marking . 15
4.3.1 General . 15
4.3.2 Coding . 16
5 Quality assessment procedures . 16
5.1 General . 16
5.1.1 Overview . 16
5.1.2 Applicability of qualification approval . 16
5.1.3 Applicability of capability approval . 16
5.1.4 Applicability of technology approval . 17
5.2 Primary stage of manufacture . 17
5.3 Subcontracting . 17
5.4 Structurally similar components . 17
5.5 Qualification approval procedures . 18
5.5.1 Eligibility for qualification approval. 18
5.5.2 Application for qualification approval . 18
5.5.3 Test procedure for qualification approval . 18
5.5.4 Granting of qualification approval . 18
5.5.5 Maintenance of qualification approval . 18
5.5.6 Quality conformance inspection . 18
5.6 Capability approval procedures . 19
5.6.1 General . 19
5.6.2 Eligibility for capability approval . 19
5.6.3 Application for capability approval . 19
5.6.4 Description of capability . 19
5.6.5 Demonstration and verification of capability . 20
5.6.6 Programme for capability approval . 21
5.6.7 Capability approval test report . 21
5.6.8 Abstract of description of capability . 21
5.6.9 Modifications likely to affect the capability approval . 21
5.6.10 Initial capability approval . 21
5.6.11 Granting of capability approval . 22
5.6.12 Maintenance of capability approval . 23
5.6.13 Extension of capability approval . 23
5.6.14 Quality conformance inspection . 23
5.7 Rework and repair . 23
5.7.1 Rework . 23
5.7.2 Repair . 24
5.8 Release for delivery . 24
5.8.1 General . 24

5.8.2 Certified records of released lots . 24
5.8.3 Delayed delivery . 24
5.8.4 Release for delivery before the completion of Group B tests . 24
5.9 Alternative test methods . 24
5.10 Unchecked parameters . 25
5.11 Characteristics and parameters for application reference . 25
5.12 Technology approval procedures . 25
5.12.1 General . 25
5.12.2 Eligibility for technology approval . 25
5.12.3 Application of technology approval . 25
5.12.4 Description of technology . 25
5.12.5 Demonstration and verification of the technology . 25
5.12.6 Granting of technology approval . 26
5.12.7 Maintenance of technology approval . 26
5.12.8 Quality conformance inspection . 26
5.12.9 Failure rate level determination . 26
5.12.10 Outgoing quality level . 26
6 Test and measurement procedures . 26
6.1 General . 26
6.2 Standard atmospheric conditions . 26
6.2.1 Standard atmospheric conditions for testing. 26
6.2.2 Recovery conditions . 27
6.2.3 Referee conditions . 27
6.2.4 Reference conditions . 27
6.3 Drying and recovery . 27
6.3.1 General . 27
6.3.2 Procedure I . 27
6.3.3 Procedure II . 27
6.4 Visual examination and check of dimensions . 28
6.4.1 Visual examination . 28
6.4.2 Marking . 28
6.4.3 Dimensions (gauging) . 28
6.4.4 Dimensions (detail) . 28
6.5 General requirements for electrical tests . 28
6.6 Varistor voltage . 29
6.7 Leakage current . 29
6.8 Capacitance . 30
6.9 Voltage proof (for insulated varistors only). 30
6.9.1 General . 30
6.9.2 V-block method . 30
6.9.3 Metal ball method . 30
6.9.4 Foil method . 30
6.10 Insulation resistance (for insulated varistors only) . 31
6.10.1 Test procedure . 31
6.10.2 Measurement and requirements . 31
6.11 Clamping voltage . 31
6.12 ESD clamping voltage (for surface mount electrostatic protective varistors
only) . 32
6.13 Maximum peak current . 32

– 4 – IEC 61051-1:2018 © IEC 2018
6.13.1 Initial measurement . 32
6.13.2 Test procedure . 32
6.13.3 Final inspection, measurement and requirements . 32
6.14 Rated average dissipation power . 32
6.14.1 General . 32
6.14.2 Initial measurement . 33
6.14.3 Test procedure . 33
6.14.4 Final inspection, measurement and requirements . 33
6.15 Rated energy . 33
6.15.1 General . 33
6.15.2 Initial measurement . 33
6.15.3 Test procedure . 34
6.15.4 Final inspection, measurement and requirements . 34
6.16 Electrostatic discharge (ESD) (for surface mount electrostatic protective
varistors only) . 35
6.16.1 Initial measurement . 35
6.16.2 Test procedure . 35
6.16.3 Final inspection, measurement and requirements . 35
6.17 Robustness of terminations . 35
6.17.1 General . 35
6.17.2 Test Ua – Tensile . 35
6.17.3 Test Ub – Bending (half of the number of terminations) . 35
6.17.4 Test Uc – Torsion (the other half of the number of terminations) . 35
6.17.5 Test Ud – Torque (for terminations with threaded studs or screws and for
integral mounting devices) . 36
6.17.6 Visual examination . 36
6.17.7 Final measurement . 36
6.17.8 Robustness of terminations of surface mount varistors . 36
6.18 Resistance to soldering heat . 37
6.18.1 Preconditioning . 37
6.18.2 Test procedure . 37
6.18.3 Recovery . 38
6.18.4 Final inspection, measurement and requirements . 38
6.19 Solderability . 38
6.19.1 General . 38
6.19.2 Test procedure . 38
6.19.3 Final inspection, measurements and requirements . 39
6.20 Rapid change of temperature . 39
6.20.1 Initial measurement . 39
6.20.2 Test procedure . 39
6.20.3 Final inspection, measurement and requirements . 39
6.21 Shock . 39
6.21.1 Initial measurement . 39
6.21.2 Test procedure . 39
6.21.3 Final inspection, measurement and requirements . 39
6.22 Vibration . 40
6.22.1 Initial measurement . 40
6.22.2 Test procedure . 40
6.22.3 Final inspection, measurement and requirements . 40

6.23 Climatic sequence . 40
6.23.1 General . 40
6.23.2 Initial measurement . 40
6.23.3 Dry heat . 40
6.23.4 Damp heat, cyclic, Test Db, first cycle . 40
6.23.5 Cold . 40
6.23.6 Low air pressure . 40
6.23.7 Damp heat, cyclic, Test Db, remaining cycles . 41
6.23.8 Final inspection, measurement and requirements . 41
6.24 Damp heat, steady state . 41
6.24.1 Initial measurement . 41
6.24.2 Test procedure . 41
6.24.3 Final inspection, measurement and requirements . 41
6.25 Fire hazard . 42
6.26 Endurance at upper category temperature . 42
6.26.1 Test system . 42
6.26.2 Initial measurement . 42
6.26.3 Mounting of the samples . 42
6.26.4 Test procedure, measurement and requirements . 43
6.27 Solvent resistance of marking . 43
6.27.1 Test procedure . 43
6.27.2 Requirements . 43
6.28 Component solvent resistance . 43
6.28.1 Initial measurements . 43
6.28.2 Test procedure . 43
6.28.3 Measurement and requirements . 44
6.29 Mounting (for surface mount varistors only) . 44
Annex A (informative) Rules for the preparation of detail specifications for capacitors
and resistors for electronic equipment . 46
Annex B (normative) Test pulses used in this specification . 47
B.1 Types of test pulses . 47
B.1.1 General . 47
B.1.2 Pulse type 1 . 47
B.1.3 Pulse type 2 (rectangular pulse) . 47
B.1.4 Pulse type 3 (ESD discharge pulse) . 47
B.2 Pulse parameters . 48
B.2.1 Value of the pulse current/voltage . 48
B.2.2 Virtual front time T . 48
B.2.3 Virtual origin O . 49
B.2.4 Virtual time to half-value T . 49
B.2.5 Virtual duration of peak of a rectangular pulse current T . 49
D
B.2.6 Virtual total duration T of a pulse current . 49
T
B.3 Tolerances for the pulses . 50
Annex C (informative) Recommended measurement/test methods for characteristics
and parameters for application reference . 51
C.1 Voltage vs. current characteristic . 51
C.2 Maximum peak current derating characteristic . 52
C.2.1 Rationale related to this test . 52
C.2.2 Failure criteria . 52

– 6 – IEC 61051-1:2018 © IEC 2018
C.2.3 Pulse life test . 52
C.2.4 Graphing of the maximum peak current derating curves . 54
C.3 Thermal resistance (for leaded varistors only) . 54
C.3.1 Test system . 54
C.3.2 Mounting of the sample . 55
C.3.3 Test procedure . 55
C.4 Abnormal overvoltage withstanding duration . 55
C.4.1 Test system . 55
C.4.2 Test procedure . 56
C.4.3 Requirements . 56

Figure 1 – General scheme for capability approval. 19
Figure 2 – Mounting method for measurement of surface mount varistors . 44
Figure B.1 – Shape of pulse current type 1 . 47
Figure B.2 – Shape of pulse voltage type 1. 48
Figure B.3 – Shape of pulse type 2 . 48
Figure B.4 – Shape of pulse type 3 . 49
Figure C.1 – Maximum peak current derating characteristic . 54

Table 1 – Standard atmospheric conditions . 27
Table 2 – Force for wire terminations . 36
Table 3 – Torque . 36
Table 4 – Number of cycles . 41
Table B.1 – Accepted differences between specified and recorded pulse values . 50
Table B.2 – Tolerances for pulse type 3 . 50

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
VARISTORS FOR USE IN ELECTRONIC EQUIPMENT –

Part 1: Generic specification
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 61051-1 has been prepared by IEC technical committee 40:
Capacitors and resistors for electronic equipment.
This third edition cancels and replaces the second edition published in 2007. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) 10 new terms and definitions – leaded varistors, surface mount varistors(SMV), electrostatic
discharge (ESD), ESD clamping voltage, equivalent rectangular pulse duration, maximum
peak current derating characteristic, rated average dissipation power, rated energy,
abnormal overvoltage withstanding duration and temperature derating curve – have been
added (see 3.6, 3.7, 3.14, 3.15, 3.19, 3.20, 3.23, 3.24, 3.25 and 3.29);
b) General requirements for electrical tests and 7 new test items – clamping voltage, ESD
clamping voltage, maximum peak current, rated average dissipation power, rated energy,
electrostatic discharge (ESD), robustness of terminations of surface mount varistors – have
been added (see 6.5, 6.11, 6.12, 6.13, 6.14, 6.15, 6.16 and 6.17.8);
c) In 6.6, 6.7, 6.8, 6.9.3, 6.23.2, 6.23.4 and 6.26, following test items have been revised:

– 8 – IEC 61051-1:2018 © IEC 2018
• Varistor voltage, leakage current and capacitance: more detailed requirements and
information have been added;
• Voltage proof – foil method: the space between the edge of the foil and each termination
has been changed from 1 mm ~ 1,5 mm to 3 mm ~ 3.5 mm for testing varistors not having
axial terminations and the minimum space between the foil and the termination has been
changed from 1 mm to 3 mm for testing varistors having axial terminations;
• Climatic sequence – dry heat: the method has been changed from Ba to Bb;
• Climatic sequence – cold: the method has been changed from Aa to Ab;
• Endurance at upper category temperature: the method of "applying test voltages in
cycles of 1,5 h on and 0,5 h off" has been changed to the method of applying test voltages
continuously throughout the test lasting for 1 000 h;
d) The test items of pulse current, voltage under pulse condition and bump have been deleted
from the section of test and measurement procedures;
e) Annex A and the contents referring to the test fixture specified in Annex A have been
deleted;
f) All contents related to silicon carbide varistors have been deleted;
g) A new normative annex entitled "Test pulses used in this specification" (Annex B) has been
added;
h) A new informative annex entitled "Recommended measurement/test methods for
characteristics and parameters for application reference" (Annex C) has been added, in
which guidelines of measuring/testing characteristics and parameters for application
reference including voltage vs. current characteristic, maximum peak current derating
characteristic, thermal resistance and abnormal overvoltage withstanding duration have
been given.
The text of this International Standard is based on the following documents:
FDIS Report on voting
40/2621/FDIS 40/2625/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.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 61051 series, published under the general title Varistors for use in
electronic equipment, can be found on the IEC website.
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.
VARISTORS FOR USE IN ELECTRONIC EQUIPMENT –

Part 1: Generic specification
1 Scope
This part of IEC 61051 is a generic specification and is applicable to varistors with symmetrical
voltage-current characteristics for use in electronic equipment.
It establishes standard terms, inspection procedures and methods of test for use in sectional
and detail specifications for quality assessment or any other purpose.
NOTE Detail specifications can be specifications within the IEC system, another specification system linked to IEC,
or specified by the manufacturer or user. The drafting of a complete detail specification by IEC technical committee 40,
if required, follows the rules described in Annex A.
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 60027 (all parts), Letter symbols to be used in electrical technology
IEC 60050 (all parts), International Electrotechnical Vocabulary (IEV)
IEC 60062, Marking codes for resistors and capacitors
IEC 60068-1:2013, Environmental testing – Part 1: General and guidance
IEC 60068-2-1:2007, Environmental testing – Part 2-1: Tests – Test A: Cold
IEC 60068-2-2:2007, Environmental testing – Part 2-2: Tests – Tests B: Dry heat
IEC 60068-2-6:2007, Environmental testing – Part 2-6: Tests – Test Fc: Vibration (Sinusoidal)
IEC 60068-2-13:1983, Environmental testing – Part 2-13: Tests – Test M: Low air pressure
IEC 60068-2-14:2009, Environmental testing – Part 2-14: Tests – Test N: Change of
temperature
IEC 60068-2-20:2008, Environmental testing – Part 2-20: Tests – Test T: Test methods for
solderability and resistance to soldering heat of devices with leads
IEC 60068-2-21:2006, Environmental testing – Part 2-21: Tests – Test U: Robustness of
terminations and integral mounting devices
IEC 60068-2-21:2006/COR1:2012
IEC 60068-2-27:2008, Environmental testing – Part 2-27: Tests – Test Ea and guidance: Shock

– 10 – IEC 61051-1:2018 © IEC 2018
IEC 60068-2-30:2005, Environmental testing – Part 2-30: Tests – Test Db: Damp heat, cyclic
(12 h + 12-hour cycle)
IEC 60068-2-45:1980, Environmental testing – Part 2-45: Tests – Test XA – Immersion in
cleaning solvents
IEC 60068-2-45:1980/AMD1:1993
IEC 60068-2-58:2015, 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 60068-2-69:2017, Environmental testing – Part 2-69: Tests – Test Te/Tc: Solderability
testing of electronic components and printed boards by the wetting balance (force
measurement) method
IEC 60068-2-78:2012, Environmental testing – Part 2-78: Tests – Test Cab: Damp heat, steady
state
IEC 60294, Measurement of the dimensions of a cylindrical component having two axial
terminations
IEC 60617, Graphical symbols for diagrams
(available at http://std.iec.ch/iec60617)
IEC 60695-11-5:2016, Fire hazard testing – Part 11-5: Test flames – Needle-flame test method
– Apparatus, confirmatory test arrangement and guidance
IEC 60717:2012, Method for the determination of the space required by capacitors and
resistors with unidirectional terminations
IEC 61000-4-2:2008, Electromagnetic Compatibility (EMC) – Part 4-2: Testing and
measurement techniques – Electrostatic discharge immunity test
IEC 61193-2, Quality assessment systems – Part 2: Selection and use of sampling plans for
inspection of electronic components and packages
IEC 61249-2-7:2002, Materials for printed boards and other interconnecting structures –
Part 2-7: Reinforced base materials clad and unclad – Epoxide woven E-glass laminated sheet
of defined flammability (vertical burning test), copper-clad
ISO 80000-1:2009, Quantities and units – Part 1: General
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
type
group of components having similar design features and the similarity of whose manufacturing
techniques enables them to be grouped together either for qualification approval or for quality
conformance inspection
Note 1 to entry: They are generally covered by a single detail specification.
Note 2 to entry: Components described in several detail specifications may, in some cases, be considered as
belonging to the same type and can therefore be grouped together for approval and quality conformance inspection.
[SOURCE: IEC 60115-1: 2008, 2.2.25, modified – The remark on "single detail specification"
has been deleted from the definition and Note 1 to entry and Note 2 to entry have been added.]
3.2
style
subdivision of a type, generally based on dimensional factors that can include several variants,
generally of a mechanical order
[SOURCE: IEC 60115-1:2008, 2.2.20]
3.3
varistor
voltage dependent resistor
VDR
component, whose conductance, at a given temperature range, increases rapidly with
...