SIST EN IEC 60539-1:2023/oprA1:2026

Amendment 1 - Directly heated negative temperature coefficient thermistors - Part 1: Generic specification

Direkt geheizte temperaturabhängige Widerstände mit negativem Temperaturkoeffizienten - Teil 1: Fachgrundspezifikation

Thermistances à coefficient de température négatif à chauffage direct - Partie 1: Spécification générique

Neposredno ogrevani termistorji z negativnim temperaturnim koeficientom - 1. del: Splošna specifikacija - Dopolnilo A1

General Information

• Status: Not Published
• Public Enquiry End Date: 28-May-2026
• ICS: 31.040.30 - Thermistors
• Technical Committee: I11 - Imaginarni 11
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 10-Mar-2026
• Due Date: 28-Jul-2026
• Ref Project: EN IEC 60539-1:2023/prA1:2026 - Amendment 1 - Directly heated negative temperature coefficient thermistors - Part 1: Generic specification

Relations

• Amends: SIST EN IEC 60539-1:2023 - Directly heated negative temperature coefficient thermistors - Part 1: Generic specification (IEC 60539-1:2022)
• Effective Date: 03-Jun-2025

Overview

SIST EN IEC 60539-1:2023/oprA1:2026 is an amendment to the foundational standard for directly heated negative temperature coefficient (NTC) thermistors, specifically Part 1: Generic specification. Developed by CLC and the IEC technical committee 40, this amendment introduces essential updates to test methods, measurement definitions, and recovery procedures, building on the requirements essential for the performance and reliability of NTC thermistors used in electronic equipment.

NTC thermistors are critical components in temperature sensing, control, and circuit protection applications. They exhibit a decrease in resistance with an increase in temperature, making them ideal for precise thermal response in various electronic systems. This standard supports manufacturers, designers, and quality assurance professionals in ensuring NTC thermistors meet consistent performance and safety criteria in a wide array of electronic assemblies.

Key Topics

The amendment addresses several key areas vital for the quality and consistency of directly heated NTC thermistors:

• Thermal Time Constant Definition:
  Refines the method for determining the thermal time constant of NTC thermistors during cooling after self-heating, specifying measurement parameters and test conditions.

• Mounting and Soldering Procedures:
  Updates soldering requirements, including specifications for silver-bearing eutectic Sn/Pb solder and flux usage, to promote consistent mounting and reliability.

• Measurement and Testing Updates:
  Clarifies procedures for initial, intermediate, and final measurements during various environmental tests (such as rapid temperature changes, thermal shock, cold, dry heat, and damp heat).

  • Emphasizes recovery under controlled atmospheric conditions for accurate testing.
  • Outlines the timing and methodology for removing and returning devices to test conditions.

• Inrush Current Limiting Evaluations:
  Details endurance, cyclic testing, and permissible capacitance procedures for thermistors designed for inrush current limiting, ensuring robust performance in demanding conditions.

• Insulation Requirements:
  Specifies insulation resistance checks for insulated thermistor types, reinforcing safety and device integrity.

Applications

This standard and its amendment apply directly to the following areas:

• Temperature Measurement:
  NTC thermistors are widely used for precise temperature monitoring in industrial controls, automotive electronics, heating/cooling systems, and consumer devices.

• Temperature Compensation:
  In circuits where temperature-induced resistance changes must be compensated for stability, including oscillators, amplifiers, and voltage regulators.

• Circuit Protection:
  Inrush current limiting thermistors protect sensitive components from surge currents when electronic devices are powered on.

• Quality Control and Production:
  Provides manufacturers and test labs with standardized methods that ensure consistent quality, durability, and compliance with international requirements.

Related Standards

Professionals working with SIST EN IEC 60539-1:2023/oprA1:2026 may also find the following standards relevant:

• EN IEC 60539-1:2023 – The main standard for directly heated NTC thermistors, Part 1: Generic specification.
• IEC 60738 series – Standards for thermistors, including other types (PTC, non-linear, etc.).
• ISO/IEC Directives, Part 1 and 2 – Fundamental rules for the preparation of international standards in electrotechnology.
• IEC TC 40 Standards – Covering other capacitors and resistors for electronic equipment.

By adhering to this amendment and the related base standard, stakeholders in the electronics industry can ensure that NTC thermistors meet both functional requirements and global compliance needs, supporting robust product design, testing, and certification workflows.

Keywords: NTC thermistor standard, SIST EN IEC 60539-1:2023/oprA1:2026, directly heated thermistor, temperature coefficient, electronic component standards, inrush current limiter, thermal testing, CLC, IEC standards.

Standards Content (Sample)

SLOVENSKI STANDARD
01-maj-2026
Neposredno ogrevani termistorji z negativnim temperaturnim koeficientom - 1. del:
Splošna specifikacija - Dopolnilo A1
Amendment 1 - Directly heated negative temperature coefficient thermistors - Part 1:
Generic specification
Direkt geheizte temperaturabhängige Widerstände mit negativem
Temperaturkoeffizienten - Teil 1: Fachgrundspezifikation
Thermistances à coefficient de température négatif à chauffage direct - Partie 1:
Spécification générique
Ta slovenski standard je istoveten z: EN IEC 60539-1:2023/prA1:2026
ICS:
31.040.30 Termistorji Thermistors
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

40/3280/CDV
COMMITTEE DRAFT FOR VOTE (CDV)

PROJECT NUMBER:
IEC 60539-1/AMD1 ED4
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2026-03-06 2026-05-29
SUPERSEDES DOCUMENTS:
40/3257/CD, 40/3276/CC
IEC TC 40 : CAPACITORS AND RESISTORS FOR ELECTRONIC EQUIPMENT
SECRETARIAT: SECRETARY:
Netherlands Mr Ronald Drenthen
OF INTEREST TO THE FOLLOWING COMMITTEES: HORIZONTAL FUNCTION(S):

ASPECTS CONCERNED:
SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING
Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of
CENELEC, is drawn to the fact that this Committee Draft for
Vote (CDV) is submitted for parallel voting.
The CENELEC members are invited to vote through the
CENELEC online voting system.
This document is still under study and subject to change. It should not be used for reference purposes.
Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of which t hey
are aware and to provide supporting documentation.
Recipients of this document are invited to submit, with their comments, notification of any relevant “In Some Countries” clau ses
to be included should this proposal proceed. Recipients are reminded that the CDV stage is the final stage for submitting ISC
clauses. (SEE AC/22/2007 OR NEW GUIDANCE DOC).

TITLE:
Amendment 1 - Directly heated negative temperature coefficient thermistors - Part 1: Generic specification

PROPOSED STABILITY DATE: 2030
NOTE FROM TC/SC OFFICERS:
electronic file, to make a copy and to print out the content for the sole purpose of preparing National Committee positions. You
may not copy or "mirror" the file or printed version of the document, or any part of it, for any other purpose without permission
in writing from IEC.
IEC CDV 60539-1 ED4.1 AMD1 © IEC 2026

1 INTERNATIONAL ELECTROTECHNICAL COMMISSION
2 ____________
4 DIRECTLY HEATED NEGATIVE TEMPERATURE
5 COEFFICIENT THERMISTORS – Part 1: Generic specification
7 AMENDMENT 1
9 FOREWORD
10 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national
11 electrotechnical committees (IEC National Committees). The object of IEC is to promote international co -operation on all
12 questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities , IEC
13 publishes International Standards, Technical Specifications, Technical Reports, Publicly Available Specifications (PAS) and G uides
14 (hereafter referred to as “IEC Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Com mittee
15 interested in the subject dealt with may participate in this preparatory work. International, governmental and non -governmental
16 organizations liaising with the IEC also participate in this preparation. IEC collaborates closely with the International Org anization
17 for Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
18 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international consensus of
19 opinion on the relevant subjects since each technical committee has representation from all interested IEC National Committee s.
20 3) IEC Publications have the form of recommendations for international use and are accepted by IEC National Committees in that
21 sense. While all reasonable efforts are made to ensure that the technical content of IEC Publications is accurate, IEC cannot be
22 held responsible for the way in which they are used or for any misinterpretation by any end user.
23 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications transparently to th e
24 maximum extent possible in their national and regional publications. Any divergence between any IEC Publication and the
25 corresponding national or regional publication shall be clearly indicated in the latter.
26 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity assessment ser vices
27 and, in some areas, access to IEC marks of conformity. IEC is not responsible for any services carried out by independent
28 certification bodies.
29 6) All users should ensure that they have the latest edition of this publication.
30 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and members of its
31 technical committees and IEC National Committees for any personal injury, property damage or other damage of any nature
32 whatsoever, whether direct or indirect, or for costs (including legal fees) and expenses arising out of the publication, use of, or
33 reliance upon, this IEC Publication or any other IEC Publications.
34 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is indispensable for
35 the correct application of this publication.
36 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
37 not be held responsible for identifying any or all such patent rights.
39 This amendment to IEC 60539-1 has been prepared by IEC technical committee 40: Capacitors and
40 resistors for electronic equipment.
41 The text of this Amendment is based on the following documents:
Draft Report on voting
XX/XX/FDIS XX/XX/RVD
43 Full information on the voting for its approval can be found in the report on voting indicated in the above
44 table.
45 The language used for the development of this International Standard is English.
IEC CDV 60539-1 ED4.1 AMD1 © IEC 2026

46 This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in accordance
47 with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available at
48 www.iec.ch/members_experts/refdocs. The main document types developed by IEC are described in
49 greater detail at www.iec.ch/publications.
50 The committee has decided that the contents of this document will remain unchanged until the stability
51 date indicated on the IEC website under webstore.iec.ch in the data related to the specific document. At
52 this date, the document will be
53 • reconfirmed,
54 • withdrawn,
55 • replaced by a revised edition, or
56 • amended.
IEC CDV 60539-1 ED4.1 AMD1 © IEC 2026

60 DIRECTLY HEATED NEGATIVE TEMPERATURE
61 COEFFICIENT THERMISTORS – Part 1: Generic specification
63 AMENDMENT 1
67 3.36 thermal time constant by cooling after self-heating
69 Change in the first paragraph sentence to be
71 time required for a thermistor to cool by 63,2 % of its temperature excess induced by self-heating, in a
72 defined medium when the current passing through an NTC thermistor in a specified medium is
73 suddenly changed from a non-zero load state to a zero load state.
75 5.4.3 Mounting on board /  5.4.3.2 Wave soldering method
77 Change the sentence in 5.4.3.2 a), first line, to be
79 The solder used shall be silver bearing (1.8 to 2.2 %) eutectic Sn/Pb solder together with non-activated
80 flux,…
82 6.8.2 Initial measurement
84 Replace the formula with this formula
86 T = T – (T – T ) × 0.632
i b b a
88 8.1 Rapid change of temperature
90 Change the sentence and item number to be
92 8.1.1 General
IEC CDV 60539-1 ED4.1 AMD1 © IEC 2026

93 The method of test shall be conducted as specified in 8.1.2 to 8.1.6.
94 ----------------------------------------------------------------------------------------------------
95 8.1.4 Intermediate measurement
96 If an intermediate measurement is to be carried out, the load shall be removed and the NTC
97 thermistors allowed to recover under standard atmospheric conditions of testing for not less than 1
98 h and not more than 2 h.
99 The appropriate parameter(s) given in the detail specification shall then be measured using
100 the method specified. The change compared with the value(s) measured in 8.1.2 shall not
101 exceed the limit specified in the relevant detail specification.
102 After intermediate measurements, the thermistors shall be returned to the conditions of
103 test. The interval between the removal from, and the return to the conditions of test for any
104 NTC thermistor shall not exceed 12 h.
105 8.1.5 Recovery
106 After completion of the test, the thermistors shall be removed and allowed to recover under
107 standard atmospheric conditions for a period of 1 h to 2 h.
109 8.1.6 Final inspection, measurements and requirements.
112 8.2 Thermal shock
...