IEC 60738-1-1:1998

Thermistors - Directly heated positive step-function temperature coefficient - Part 1-1: Blank detail specification - Current limiting application - Assessment level EZ

General Information

• Status: Published
• Publication Date: 02-Dec-1998
• ICS: 31.040.30 - Thermistors
• Technical Committee: TC 40 - Capacitors and resistors for electronic equipment
• Current Stage: DELPUB - Deleted Publication
• Start Date: 13-Feb-2008
• Completion Date: 26-Oct-2025

Relations

• Revised: IEC 60738-1-1:2008 - Thermistors - Directly heated positive step-function temperature coefficient - Part 1-1: Blank detail specification - Current limiting application - Assessment level EZ
• Effective Date: 05-Sep-2023

Overview

IEC 60738-1-1:1998 is a blank detail specification published by the IEC for directly heated positive step-function temperature coefficient (PTC) thermistors intended for current-limiting applications at assessment level EZ. The document provides a template and mandatory structure for manufacturer detail specifications that supplement the generic requirements of IEC 60738-1. Its purpose is to ensure consistent presentation of product data, inspection procedures and test schedules so components can be compared and assessed for quality and interchangeability.

Key Topics

• Scope and purpose: A blank detail specification defines style, layout and minimum content required for specific thermistor detail specifications. Detail specifications that do not follow it should not be described as IEC compliant.
• Identification and outline: Requires identification of the issuing body, detail-specification number, short description of thermistor type, typical construction notes, outline drawings and assessment level (EZ).
• Electrical data and ratings: Specifies the electrical parameters and limits that must be provided, including zero-power resistance, maximum voltage, tripping current, maximum non-tripping current, residual and overload currents, switching temperature and dissipation factor.
• Materials, coating and terminations: States whether coatings are insulating, the materials and colors, whether terminations are suitable for soldering, and acceptable connection methods (welding, crimping, clamping).
• Inspection and test schedules: Defines lot-by-lot (Group A/B) and periodic (Group C) inspection requirements, sampling plans, and lists required tests such as visual inspection, solderability/soldering heat resistance, vibration, shock/bump, climatic sequences, rapid temperature change and thermal time constant measurements.

Applications

This blank detail specification is directly applicable to:

• Manufacturers preparing product detail specifications for current-limiting PTC thermistors.
• Component engineers and quality managers who need to verify compliance with IEC requirements for electrical protection devices.
• Purchasing and approvals teams requiring standardized information for registration in component approval registers (IECQ / QC references).

Practical benefits include improved product interchangeability, clearer ordering information (style, maximum continuous AC voltage, detail-specification reference), and well-defined test methods to assess reliability for end-use in power supplies, surge protectors and inrush limiting.

Related Standards

• IEC 60738-1:1998 - Generic specification for directly heated positive step-function PTC thermistors (referenced as the base document).
• IEC 60050 - International Electrotechnical Vocabulary (terminology).
• IEC 60027, IEC 60417, IEC 60617 - Letter and graphical symbol standards for marking and diagrams.
• IEC 60068 - Environmental testing standards (referred to for vibration, climatic and soldering tests).

Note: The blank detail specification references IEC Quality Assessment System identifiers (QC 440001) and is intended as a mandatory template; it does not itself list component-specific numerical values, which must be provided in the completed detail specification.

Standards Content (Sample)

INTERNATIONAL
IEC
STANDARD
60738-1-1
QC 440001
Second edition
1998-12
Thermistors –
Directly heated positive step-function
temperature coefficient –
Part 1-1:
Blank detail specification –
Current limiting application – Assessment level EZ
Thermistances à basculement à coefficient de température
positif à chauffage direct –
Partie 1-1:
Spécification particulière cadre –
Application pour limitation de courant –
Niveau d’assurance EZ
Reference number
Numbering
As from 1 January 1997 all IEC publications are issued with a

designation in the 60000 series.

Consolidated publications
Consolidated versions of some IEC publications including

amendments are available. For example, edition numbers 1.0, 1.1

and 1.2 refer, respectively, to the base publication, the base

publication incorporating amendment 1 and the base publication
incorporating amendments 1 and 2.
Validity of this publication
The technical content of IEC publications is kept under constant
review by the IEC, thus ensuring that the content reflects current
technology.
Information relating to the date of the reconfirmation of the
publication is available in the IEC catalogue.
Information on the subjects under consideration and work in
progress undertaken by the technical committee which has prepared
this publication, as well as the list of publications issued, is to be
found at the following IEC sources:
• IEC web site*
• Catalogue of IEC publications
Published yearly with regular updates
(On-line catalogue)*
• IEC Bulletin
Available both at the IEC web site* and as a printed periodical
Terminology, graphical and letter symbols
For general terminology, readers are referred to IEC 60050: International
Electrotechnical Vocabulary (IEV).
For graphical symbols, and letter symbols and signs approved by the IEC for
general use, readers are referred to publications IEC 60027: Letter symbols to be
used in electrical technology, IEC 60417: Graphical symbols for use on equipment.

Index, survey and compilation of the single sheets and IEC 60617: Graphical symbols
for diagrams.
* See web site address on title page.

INTERNATIONAL
IEC
STANDARD
60738-1-1
QC 440001
Second edition
1998-12
Thermistors –
Directly heated positive step-function
temperature coefficient –
Part 1-1:
Blank detail specification –
Current limiting application – Assessment level EZ
Thermistances à basculement à coefficient de température
positif à chauffage direct –
Partie 1-1:
Spécification particulière cadre –
Application pour limitation de courant –
Niveau d’assurance EZ
 IEC 1998  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 Geneva, Switzerland
Telefax: [phone] e-mail: [e-mail] IEC web site http://www.iec.ch
Commission Electrotechnique Internationale
PRICE CODE
L
International Electrotechnical Commission
For price, see current catalogue

– 2 – 60738-1-1 © IEC:1998(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
THERMISTORS –
DIRECTLY HEATED POSITIVE STEP-FUNCTION

TEMPERATURE COEFFICIENT –
Part 1-1: Blank detail specification –

Current limiting application – Assessment level EZ
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical reports or guides and they are accepted by the National Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60738-1-1 has been prepared by IEC technical committee 40:
Capacitors and resistors for electronic equipment.

This second edition cancels and replaces the first edition published in 1982.
The text of this standard is based on the following documents:
FDIS Report on voting
40/1081/FDIS 40/1097/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.
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).

60738-1-1 © IEC:1998(E) – 3 –
THERMISTORS –
DIRECTLY HEATED POSITIVE STEP-FUNCTION

TEMPERATURE COEFFICIENT –
Part 1-1: Blank detail specification –

Current limiting application – Assessment level EZ

INTRODUCTION
Blank detail specification
A blank detail specification is a supplementary document to the generic specification and
contains requirements for style and layout and minimum content of detail specifications. Detail
specifications not complying with these requirements shall not be considered as being in
accordance with IEC specifications nor shall they so be described.
In the preparation of detail specifications the content of 1.4 of the generic specification shall be
taken into account.
The numbers between brackets on the first page correspond to the following information which
shall be inserted in the position indicated.
Identification of the detail specification
[1] The "International Electrotechnical Commission" or the National Standards Organization
under whose authority the detail specification is drafted.
[2] The IEC or National Standards number of the detail specification, date of issue and any
further information required by the national system.
[3] The number and issue number of the IEC or national generic specification.
[4] The IEC number of the blank detail specification.
Identification of the thermistor
[5] A short description of the type of thermistor.
[6] Information on typical construction (if applicable).
NOTE – When the thermistor is not designed for use on printed boards, this should clearly be stated in the detail
specification in this position.

[7] Outline drawing with main dimensions which are of importance for interchangeability
and/or reference to the national or international documents for outlines. Alternatively, this
drawing may be given in an annex to the detail specification.
[8] Application or group of applications covered and/or assessment level.
[9] Reference data on the most important properties, to allow comparison between the various
thermistor types.
– 4 – 60738-1-1 © IEC:1998(E)
[1] IEC 60738-1-1-XXX [2]
QC 440001XXXXXX
ELECTRONIC COMPONENTS OF ASSESSED IEC 60738-1-1 [4]

QUALITY IN ACCORDANCE WITH: QC 440001

[3] DIRECTLY HEATED POSITIVE
STEP-FUNCTION TEMPERATURE
COEFFICIENT THERMISTORS [5]
Outline drawing: [see 1.2] FOR CURRENT LIMITING
[. angle projection] APPLICATION
MODIFIED FERRO-ELECTRIC [6]
[7] CERAMIC MATERIAL
[Other shapes are permitted within the dimensions given]
Assessment level: EZ [8]
Information on the availability of components
[9]
qualified to this detail specification is given in
the Register of Approvals.
1 General data
1.1 Method(s) of mounting (to be inserted)
(See 4.12.1 of IEC 60738-1.)
1.2 Dimensions
(All dimensions are in millimetres or inches and millimetres; it shall be stated which dimensions
are suitable for gauging.)
Dimensioned drawing(s) shall be given in the detail specification. If necessary, the dimensions
may be listed in tabular form with reference to styles or codes.
1.3 Coating
The detail specification shall state:
a) whether the coating is insulating or non-insulating;
b) the material;
c) the colour, if applicable.
60738-1-1 © IEC:1998(E) – 5 –
1.4 Terminations
The detail specification shall state whether the terminations are suitable for soldering. If they are

not, suitable methods of connection shall be stated for example: welding, clamping or crimping.

1.5 Flammability
The detail specification shall state whether the thermistor is actively or passively flammable if

applicable. The test method shall be given in the test schedule.

1.6 Resistance to solvents
The detail specification shall state whether the coating and the marking of the thermistor are
solvent resistant if applicable. The test methods shall be given in the test schedule.
1.7 Packaging
The detail specification shall give the following information (if required):
a) whether bulk packed or taped and if taped, drawing or references;
b) the dimensions of the immediate packaging and the number of thermistors packed;
c) the dimensions of the outer package and the number of immediate packages;
d) methods of disposal of the packaging material.
1.8 Electrical data/Ratings and characteristics
The detail specification shall give units and tolerances or limiting values for the following para-
meters. If necessary, electrical data may be listed in tabular form, with reference to styles and codes.
Upper/Lower category temperatures (UCT/LCT);
Operating temperature range at maximum voltage;
Maximum voltage (U );
max.
Zero-power resistance (R );
T
Isolation voltage (insulated thermistors only);
Insulation resistance (insulated thermistors only);
Tripping current (I );
t
Maximum non-tripping current (I );
max. nt
Residual current at U (I );
max. res
Maximum overload current (I
...