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---------------------- Page: 1 ----------------------

EUROPEAN STANDARD
EN 60738-1

NORME EUROPÉENNE
June 2006
EUROPÄISCHE NORM

ICS 31.040.30


English version


Thermistors -
Directly heated positive temperature coefficient
Part 1: Generic specification
(IEC 60738-1:2006)


Thermistances à coefficient  Direkt geheizte temperaturabhängige
de température positif Widerstände mit positivem
à chauffage direct Temperaturkoeffizienten
Partie 1: Spécification générique Teil 1: Fachgrundspezifikation
(CEI 60738-1:2006) (IEC 60738-1:2006)




This European Standard was approved by CENELEC on 2006-05-01. 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, 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


© 2006 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60738-1:2006 E

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EN 60738-1:2006 - 2 -

Foreword
The text of document 40/1651/FDIS, future edition 3 of IEC 60738-1, prepared by IEC TC 40, Capacitors
and resistors for electronic equipment, was submitted to the IEC-CENELEC parallel vote and was
approved by CENELEC as EN 60738-1 on 2006-05-01.
This European Standard supersedes EN 60738-1:1999.
The changes with respect to EN 60738-1:1999 refer to the tables, figures and references.
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) 2007-02-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2009-05-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60738-1:2006 was approved by CENELEC as a European
Standard without any modification.
__________

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- 3 - EN 60738-1:2006

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 60027 Series Letter symbols to be used in electrical HD 60027 Series
technology


IEC 60050 Series International Electrotechnical Vocabulary - -
(IEV)


IEC 60062 (mod) 2004 Marking codes for resistors and capacitors EN 60062 2005


IEC 60068-1 1988 Environmental testing -
+ corr. October 1988 Part 1: General and guidance
+ A1 1992 EN 60068-1 1994


IEC 60068-2-1 1990 Environmental testing - EN 60068-2-1 1993
+ A1 1993 Part 2: Tests - Tests A: Cold + A1 1993
+ A2 1994 + A2 1994


IEC 60068-2-2 1974 Basic environmental testing procedures - EN 60068-2-2 1993

+ A1 1993 Part 2: Tests - Tests B: Dry heat + A1 1993


1) 2)
IEC 60068-2-6 - Environmental testing - EN 60068-2-6 1995
 Part 2: Tests - Test Fc: Vibration (sinusoidal)


1) 2)
IEC 60068-2-11 - Environmental testing - EN 60068-2-11 1999
 Part 2: Tests - Test Ka: Salt mist


1) 2)
IEC 60068-2-13 - Environmental testing - EN 60068-2-13 1999
Part 2: Tests - Test M: Low air pressure


IEC 60068-2-14 1984 Environmental testing -
+ A1 1986 Part 2: Tests - Test N: Change of temperature EN 60068-2-14 1999


IEC 60068-2-20 1979 Basic environmental testing procedures -
+ A2 1987 Part 2: Tests - Test T: Soldering HD 323.2.20 S3 1988


1) 2)
IEC 60068-2-21 - Environmental testing - EN 60068-2-21 1999
Part 2-21: Tests - Test U: Robustness of
terminations and integral mounting devices


1) 2)
IEC 60068-2-27 - Basic environmental testing procedures - EN 60068-2-27 1993
Part 2: Tests - Test Ea and guidance: Shock


1) 2)
IEC 60068-2-29 - Basic environmental testing procedures - EN 60068-2-29 1993
Part 2: Tests - Test Eb and guidance: Bump



1)
Undated reference.
2)
Valid edition at date of issue.

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EN 60738-1:2006 - 4 -
Publication Year Title EN/HD Year
IEC 60068-2-30 2005 Environmental testing - EN 60068-2-30 2005
Part 2-30: Tests - Test Db: Damp heat, cyclic
(12 h + 12 h cycle)


IEC 60068-2-45 1980 Basic environmental testing procedures - EN 60068-2-45 1992
Part 2: Tests - Test Xa and guidance:
Immersion in cleaning solvents


1) 2)
IEC 60068-2-58 - 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)


1) 2)
IEC 60068-2-78 - Environmental testing - EN 60068-2-78 2001
Part 2-78: Tests - Test Cab: Damp heat,
steady state


1)
IEC 60294 - Measurement of the dimensions of a - -
cylindrical component having two axial
terminations


1)
IEC 60410 - Sampling plans and procedures for inspection - -
by attributes


IEC 60617 data- Graphical symbols for diagrams - - -
base


1)
IEC 60717 - Method for the determination of the space - -
required by capacitors and resistors with
unidirectional terminations


1) 2)
IEC 61249-2-7 - Materials for printed boards and other EN 61249-2-7 2002
interconnecting structures - + corr. September 2005
Part 2-7: Reinforced base materials, clad and
unclad - Epoxide woven E-glass laminated
sheet of defined flammability (vertical burning
test), copper-clad


1) 2)
IEC 61760-1 - Surface mounting technology - EN 61760-1 2006
Part 1: Standard method for the specification
of surface mounting components (SMDs)


1)
IEC QC 001002-3 - IEC Quality Assessment System for - -
Electronic Components (IECQ) - Rules of
Procedure - Part 3: Approval procedures


1)
ISO 1000 - SI units and recommendations for the use of - -
their multiples and of certain other units

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INTERNATIONAL IEC


STANDARD 60738-1





QC 440000

Third edition
2006-04

Thermistors – Directly heated positive
temperature coefficient –
Part 1:
Generic specification


 IEC 2006  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
PRICE CODE
Commission Electrotechnique Internationale XA
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue

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– 2 – 60738-1  IEC:2006(E)
CONTENTS
FOREWORD.5

1 Scope.7
2 Normative references .7
3 Terms and definitions .8
4 Units and symbols .16
5 Preferred values.17
5.1 Climatic categories.17
5.2 Marking .17
5.3 Spacings .18
6 Quality assessment procedures.18
6.1 General .18
6.2 Primary stage of manufacture.19
6.3 Subcontracting .19
6.4 Structurally similar components.19
6.5 Qualification approval procedures .20
6.6 Rework and repair .27
6.7 Release for delivery .27
6.8 Certified test records of released lots .28
6.9 Delayed delivery.28
6.10 Alternative test methods .28
6.11 Manufacture outside the geographical limits of IECQ NSIs .28
6.12 Unchecked parameters.28
7 Test and measurement procedures.28
7.1 General .28
7.2 Standard conditions for testing .29
7.3 Drying and recovery .29
7.4 Visual examination and check of dimensions.30
7.5 Zero-power resistance.30
7.6 Temperature coefficient of resistance.31
7.7 Insulation resistance (for insulated types only) .31
7.8 Voltage proof (for insulated types only) .32
7.9 Resistance/temperature characteristic.32
7.10 Dissipation factor at U (δ) .33
max
7.11 Response time by ambient temperature change (t ) .34
a
7.12 Response time by power change (t ).34
p
7.13 Thermal time constant by ambient temperature change (τ ) .35
a
7.14 Thermal time constant by cooling (τ ).35
c
7.15 Robustness of terminations .37
7.16 Solderability .38
7.17 Resistance to soldering heat .39
7.18 Rapid change of temperature .40
7.19 Vibration.40
7.20 Bump .40
7.21 Shock.41

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60738-1  IEC:2006(E) – 3 –
7.22 Climatic sequence .41
7.23 Damp heat, steady state.42
7.24 Endurance.43
7.25 Tripping current and tripping time .46
7.26 Non-tripping current .47
7.27 Residual current .47
7.28 Surface temperature.47
7.29 Inrush current.48
7.30 Mounting (for surface mount thermistors only) .49
7.31 Shear (adhesion) test .50
7.32 Substrate bending test .50

Annex A (normative) Interpretation of sampling plans and procedures as described in
IEC 60410 for use within the IEC quality assessment system for electronic
components (IECQ) .51
Annex B (informative) Mounting for electrical measurements (except surface mount
types) .52
Annex C (informative) Mounting for temperature measurements .55

Figure 1 – Typical resistance-temperature characteristic and definitions for PTC
thermistors (at zero power) .10
Figure 2 – Typical R-TNF characteristic for PTC thermistors in sensor applications .11
Figure 3 – Typical current/voltage characteristic for PTC thermistors .11
Figure 4 – I against t at U .14
in dc
Figure 5 – I against t at U .15
in rms
Figure 6 – Dissipation factor test circuit .33
Figure 7 – Temperature gradient.34
Figure 8 – Circuit for measurement of thermal time constant by cooling.36
Figure 9 – Circuit for endurance at maximum operating temperature and maximum
voltage.45
Figure 10 – Circuit for surface temperature measurement.48
Figure 11 – Measuring circuit.48
Figure B.1 – Example of a preferred mounting method for thermistors without wire
terminations.52
Figure B.2 – Example of a preferred mounting method for thermistors with wire
terminations.53
Figure B.3 – Example of a preferred mounting method for surface mount thermistors .54
Figure C.1 – Example of a preferred mounting method for temperature measurement
on cylindrical heating elements .55

Table 1 – Creepage distances and clearances .18
Table 2 – Fixed sample size test schedule for qualification approval of thermistors for
current limitation – Assessment level EZ.22
Table 3 – Fixed sample size test schedule for qualification approval of thermistors for
use as heating elements – Assessment level EZ.23
Table 4 – Fixed sample size test schedule for qualification approval of thermistors for
inrush current application – Assessment level EZ .24
Table 5 – Fixed sample size test schedule for qualification approval of thermistors for
use as temperature sensing elements, Assessment level EZ .25

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– 4 – 60738-1  IEC:2006(E)
Table 6 – Quality conformance inspection for lot-by-lot inspection .26
Table 7 – Quality conformance inspection for periodic testing .27
Table 8 – Tensile force .37
Table 9 – Number of cycles per climatic category .42

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60738-1  IEC:2006(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

THERMISTORS – DIRECTLY HEATED POSITIVE
TEMPERATURE COEFFICIENT –

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 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 60738-1 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 1998 and constitutes a
minor revision. The changes with respect to the previous edition refer to the tables, figures
and references.
The text of this standard is based on the following documents:
FDIS Report on voting
40/1651/FDIS 40/1730/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.

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– 6 – 60738-1  IEC:2006(E)
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The QC number that appears on the front cover of this publication is the specification number
in the IEC Quality Assessment System for Electronic Components (IECQ).
IEC 60738 consists of the following parts, under the general title Thermistors – Directly
heated positive step-function coefficient:
Part 1: Generic specification
Part 1-1: Blank detail specification – Current limiting application – Assessment level EZ
Part 1-2: Blank detail specification – Heating element application – Assessment level EZ
Part 1-3: Blank detail specification – Inrush current application – Assessment level EZ
Part 1-4: Blank detail specification – Sensing application – Assessment level EZ
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 standard may be issued at a later date.

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60738-1  IEC:2006(E) – 7 –
THERMISTORS – DIRECTLY HEATED POSITIVE
TEMPERATURE COEFFICIENT –

Part 1: Generic specification



1 Scope
This part of IEC 60738 describes terms and methods of test for positive step-function
temperature coefficient thermistors, insulated and non-insulated types typically made from
ferro-electric semi-conductor materials.
It establishes standard terms, inspection procedures and methods of test for use in detail
specifications for Qualification Approval and for Quality Assessment Systems for electronic
components.
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 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 60068-1:1988, Environmental testing – Part 1: General and guidance
Amendment 1 (1992)
IEC 60068-2-1:1990, Environmental testing – Part 2: Tests – Tests A: Cold
Amendment 1 (1993)
Amendment 2 (1994)
IEC 60068-2-2:1974, Environmental testing – Part 2: Tests – Tests B: Dry heat
Amendment 1 (1993)
IEC 60068-2-6, Environmental testing – Part 2: Tests – Test Fc: Vibration (sinusoidal)
IEC 60068-2-11, Environmental testing – Part 2: Tests – Test Ka: Salt mist
IEC 60068-2-13, Environmental testing – Part 2: Tests – Test M: Low air pressure
IEC 60068-2-14:1984, Environmental testing – Part 2: Tests – Test N: Change of temperature
Amendment 1 (1986)
IEC 60068-2-20:1979, Environmental testing – Part 2: Tests – Test T: Soldering
Amendment 2 (1987)
IEC 60068-2-21, Environmental testing – Part 2-21: Tests – Test U: Robustness of
terminations and integral mounting devices

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– 8 – 60738-1  IEC:2006(E)
IEC 60068-2-27, Environmental testing – Part 2: Tests – Test Ea and guidance: Shock
IEC 60068-2-29, Environmental testing – Part 2: Tests – Test Eb and guidance: Bump
IEC 60068-2-30:2005, Environmental testing – Part 2: Tests – Test Db: Damp heat, cyclic
(12 h + 12-hour cycle)
IEC 60068-2-45:1980, Environmental testing – Part 2: Tests – Test XA and guidance –
Immersion in cleaning solvents
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 60068-2-78, 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 60410, Sampling plans and procedures for inspection by attributes
1
IEC 60617 (all parts) [DB] : Graphical symbols for diagrams
IEC 60717, Method for determination of the space required by capacitors and resistors with
unidirectional terminations
IEC 61249-2-7, 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 61760-1, Surface mounting technology – Part 1: Standard method for the specification of
surface mounting components (SMDs)
IEC QC 001002-3, Rules of Procedure of the IEC Quality Assessment System for Electronic
Components (IECQ) – Part 3: Approval procedures
ISO 1000, SI units and recommendations for the use of their multiples and of certain other
units
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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
They are generally covered by a single detail specification
NOTE Components described in several detail specifications, may, in some cases, be considered as belonging to
the same type but they are generally covered by a single detail specification.
—————————
1
“DB” refers to the IEC on-line database.

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60738-1  IEC:2006(E) – 9 –
3.2
style
variation within a type having specific nominal dimensions and characteristics
3.3
thermistor
thermally sensitive semiconducting resistor which exhibits a significant change in electrical
resistance with a change in body temperature
3.4
positive temperature coefficient thermistor
thermistor, the resistance of which inc
...