IEC 60539-1:2016

IEC 60539-1 ®
Edition 3.0 2016-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Directly heated negative temperature coefficient thermistors –
Part 1: Generic specification
Thermistances à coefficient de température négatif à chauffage direct –
Partie 1: Spécification générique

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IEC 60539-1 ®
Edition 3.0 2016-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Directly heated negative temperature coefficient thermistors –

Part 1: Generic specification
Thermistances à coefficient de température négatif à chauffage direct –

Partie 1: Spécification générique

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.040.30 ISBN 978-2-8322-3307-8

– 2 – IEC 60539-1:2016  IEC 2016
CONTENTS
FOREWORD . 7
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 10
4 General items . 20
4.1 Units and symbols. 20
4.2 Preferred values and appropriate category . 20
4.2.1 General . 20
4.2.2 Appropriate category . 20
4.3 Marking . 20
4.3.1 General . 20
4.3.2 Marking for small size types such as surface mount thermistors . 21
4.3.3 Coding . 21
4.4 Quality assessment procedures . 21
5 Test and measurement procedures . 21
5.1 General . 21
5.2 Standard atmospheric conditions for testing . 21
5.3 Drying and recovery . 22
5.3.1 Drying . 22
5.3.2 Recovery . 22
5.4 Mounting (for surface mount thermistors only) . 22
5.4.1 General . 22
5.4.2 Substrate and pad . 22
5.4.3 Mounting on board . 22
5.5 Visual examination and check of dimensions . 23
5.5.1 Visual examination . 23
5.5.2 Dimensions . 24
5.6 Zero-power resistance . 24
5.6.1 General . 24
5.6.2 Measurement procedures . 24
5.6.3 Requirements . 24
5.7 B-value or resistance ratio . 25
5.7.1 General . 25
5.7.2 Requirements . 25
5.8 Insulation resistance (for insulated types only) . 25
5.8.1 General . 25
5.8.2 Test methods . 25
5.8.3 Applied voltage . 27
5.8.4 Requirements . 28
5.9 Voltage proof (for insulated types only) . 28
5.9.1 General . 28
5.9.2 Test voltage . 28
5.9.3 Requirements . 28
5.10 Resistance/temperature characteristic . 28
5.10.1 General . 28
5.10.2 Test methods . 28

5.10.3 Requirements . 28
5.11 Dissipation factor (δ) . 28
5.11.1 General . 28
5.11.2 Initial measurements . 29
5.11.3 Test methods . 29
5.11.4 Requirements . 30
5.12 Thermal time constant by ambient temperature change (τ ) . 30
a
5.12.1 The hot to cold thermal time constant for ambient temperature change . 30
5.12.2 The cold to hot thermal time constant for ambient temperature change . 31
5.12.3 Final measurements and requirements . 31
5.12.4 Requirements . 31
5.13 Thermal time constant by cooling after self-heating (τ ) . 31
c
5.13.1 General . 31
5.13.2 Initial measurements . 31
5.13.3 Preconditioning . 32
5.13.4 Test method . 32
5.13.5 Final measurements and requirements . 32
5.14 Robustness of terminations (not applicable to surface mount thermistors) . 33
5.14.1 General . 33
5.14.2 Initial measurements . 33
5.14.3 Test methods . 33
5.14.4 Test Ua – Tensile . 33
5.14.5 Test Ub – Bending (half the number of terminations) . 33
5.14.6 Test Uc – Torsion (remaining terminations). 33
5.14.7 Final measurements and requirements . 34
5.15 Resistance to soldering heat . 34
5.15.1 General . 34
5.15.2 Preconditioning . 34
5.15.3 Test procedure . 34
5.15.4 Recovery . 34
5.15.5 Final inspection, measurement and requirements . 34
5.16 Solderability . 35
5.16.1 General . 35
5.16.2 Test procedure . 35
5.16.3 Final inspection, measurements and requirements. 35
5.17 Rapid change of temperature . 35
5.17.1 General . 35
5.17.2 Initial measurements . 35
5.17.3 Test procedures . 35
5.17.4 Final inspection, measurements and requirements. 36
5.18 Vibration . 36
5.18.1 General . 36
5.18.2 Initial measurements . 36
5.18.3 Test procedures . 36
5.18.4 Final inspection, measurements and requirements. 36
5.19 Shock . 37
5.19.1 General . 37
5.19.2 Initial measurements . 37

– 4 – IEC 60539-1:2016  IEC 2016
5.19.3 Mounting . 37
5.19.4 Test procedures . 37
5.19.5 Final inspection, measurements and requirements. 37
5.20 Free fall . 37
5.20.1 General . 37
5.20.2 Initial measurements . 37
5.20.3 Test procedures . 37
5.20.4 Final inspection, measurements and requirements. 37
5.21 Thermal shock . 37
5.21.1 General . 37
5.21.2 Initial measurements . 38
5.21.3 Test procedures . 38
5.21.4 Final inspection, measurements and requirements. 38
5.22 Cold . 38
5.22.1 General . 38
5.22.2 Initial measurements . 38
5.22.3 Test procedures . 38
5.22.4 Final inspection, measurements and requirements. 39
5.23 Dry heat . 39
5.23.1 General . 39
5.23.2 Initial measurements . 39
5.23.3 Test procedures . 39
5.23.4 Final inspection, measurements and requirements. 39
5.24 Damp heat, steady state . 39
5.24.1 General . 39
5.24.2 Initial measurements . 40
5.24.3 Test procedures . 40
5.24.4 Recovery . 40
5.24.5 Final inspection, measurements and requirements. 40
5.25 Endurance . 40
5.25.1 General . 40
5.25.2 Endurance at room temperature with applied continuous maximum
current (I ) (for inrush current-limiting thermistors only) . 40
max25
5.25.3 Endurance at room temperature with applied cyclic maximum current
(I ) (for inrush current-limiting thermistors only) . 41
max25
5.25.4 Endurance at T and P . 42
3 max
5.25.5 Endurance at upper category temperature . 43
5.25.6 Maximum permissible capacitance (for inrush current-limiting
thermistors only) . 44
5.26 Shear (adhesion) test (for surface mount thermistors only) . 45
5.26.1 General . 45
5.26.2 Test conditions . 46
5.26.3 Requirements . 46
5.27 Substrate bending test (for surface mount thermistors only) . 46
5.27.1 General . 46
5.27.2 Initial measurements . 46
5.27.3 Test procedures . 46
5.27.4 Final inspection and requirements . 46
5.28 Component solvent resistance . 46
5.28.1 General . 46

5.28.2 Initial measurements . 47
5.28.3 Test conditions . 47
5.28.4 Requirements . 47
5.29 Solvent resistance of marking . 47
5.29.1 General . 47
5.29.2 Test conditions . 47
5.29.3 Requirements . 47
5.30 Salt mist . 47
5.30.1 General . 47
5.30.2 Test conditions . 47
5.31 Sealing . 47
5.32 Composite temperature/humidity cycle . 48
5.32.1 General . 48
5.32.2 Initial measurements . 48
5.32.3 Test conditions . 48
5.32.4 Final inspection, measurements and requirements. 48
Annex A (normative) Interpretation of sampling plans and procedures as described in
IEC 60410:1973 for use within quality assessment systems . 49
A.1 Clause and subclause numbers of IEC 60410:1973 . 49
Annex B (normative) Rules for the preparation of detail specifications for directly
heated thermistors for electronic equipment for use within quality assessment systems . 50
B.1 Drafting . 50
B.2 Reference standard . 50
B.3 Circulation . 50
Annex C (informative) Typical examples of mountings for measurements of directly
heated thermistors . 51
C.1 Mounting for surface mount thermistors . 51
Annex D (informative) Reference to IEC 60539-1:2008 . 53
Annex Q (normative) Quality assessment procedures . 54
Q.1 General . 54
Q.2 Primary stage of manufacture . 54
Q.3 Structurally similar components . 54
Q.4 Qualification approval procedures . 55
Q.4.1 General . 55
Q.4.2 Test procedure for qualification approval . 55
Q.4.3 Maintenance of qualification approval . 55
Q.5 Quality conformance inspection . 56
Q.6 Certified test records of released lots . 56
Q.7 Delayed delivery . 56
Q.8 Release for delivery under qualification approval before the completion of
group B tests . 56
Q.9 Alternative test methods . 56
Q.10 Unchecked parameters . 56
Bibliography . 57

Figure 1 – Typical resistance-temperature characteristic for NTC thermistors . 13
Figure 2 – Decreased power dissipation curve . 15
Figure 3 – Maximum current derating . 17

– 6 – IEC 60539-1:2016  IEC 2016
Figure 4 – Basic circuit for zero-power resistance measurement . 24
Figure 5 – Example of Method 1 for testing the insulation resistance . 25
Figure 6 – Example of Method 2 for testing the insulation resistance (1) . 26
Figure 7 – Example of Method 2 for testing the insulation resistance (2) . 26
Figure 8 – Example of Method 3 for testing the insulation resistance . 27
Figure 9 – Example of Method 4 for testing the insulation resistance . 27
Figure 10 – Example of test chamber . 29
Figure 11 – Dissipation factor measuring circuit . 30
Figure 12 – Thermal time constant measuring circuit . 32
Figure 13 – Endurance at room temperature with I evaluating circuit . 41
max25
Figure 14 – Maximum permissible capacitance test circuit (Method 1) . 44
Figure 15 – Maximum permissible capacitance test circuit (Method 2) . 45
Figure C.1 – Mounting for measurements of surface mount thermistors . 52

Table 1 – Lower and upper category temperatures and duration of the damp heat,
steady state test . 20
Table 2 – Tensile force . 33

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DIRECTLY HEATED NEGATIVE TEMPERATURE
COEFFICIENT THERMISTORS –
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
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6) All users should ensure that they have the latest edition of this publication.
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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 60539-1 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 2008. This edition
constitutes a technical revision. Tables, figures and references have been revised.
The text of this standard is based on the following documents:
FDIS Report on voting
40/2430/FDIS 40/2457/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.

– 8 – IEC 60539-1:2016  IEC 2016
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 60539 series, published under the general title Directly heated
negative temperature coefficient thermistors, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website 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.
The contents of the corrigendum of September 2017 have been included in this copy.

DIRECTLY HEATED NEGATIVE TEMPERATURE
COEFFICIENT THERMISTORS –
Part 1: Generic specification
1 Scope
This part of IEC 60539 is applicable to directly heated negative temperature coefficient
thermistors, typically made from transition metal oxide materials with semiconducting
properties.
It establishes standard terms, inspection procedures and methods of test for use in sectional
and detail specifications of electronic components for quality assessment or any other
purpose.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60062, Marking codes for resistors and capacitors
IEC 60068-1:2013, Environmental testing – Part 1: General and guidance
IEC 60068-2-1, Environmental testing – Part 2-1: Tests – Tests A: Cold
IEC 60068-2-2, Environmental testing – Part 2-2: Tests – Tests B: Dry heat
IEC 60068-2-6, Environmental testing – Part 2-6: Tests – Test Fc: Vibration (sinusoidal)
IEC 60068-2-11, Basic environmental testing procedures – Part 2-11: Tests – Test Ka: Salt
mist
IEC 60068-2-14, Environmental testing – Part 2-14: Tests – Test N: Change of temperature
IEC 60068-2-17, Basic environmental testing procedures – Part 2-17: Tests – Test Q: Sealing
IEC 60068-2-20, 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, Environmental testing – Part 2-21: Tests – Test U: Robustness of
terminations and integral mounting devices
IEC 60068-2-27, Environmental testing – Part 2-27: Tests – Test Ea and guidance: Shock
IEC 60068-2-31, Environmental testing – Part 2-31: Tests – Test Ec: Rough handling shocks,
primarily for equipment-type specimens
IEC 60068-2-38, Environmental testing – Part 2-38: Tests – Test Z/AD: Composite
temperature/humidity cyclic test

– 10 – IEC 60539-1:2016  IEC 2016
IEC 60068-2-45:1980, Basis Environmental testing procedures – Part 2-45: Tests – Test XA
and guidance: Immersion in cleaning solvents
IEC 60068-2-45:1980/AMD1:1993
IEC 60068-2-52, Environmental testing – Part 2-52: Tests – Test Kb: Salt mist, cyclic (sodium
chloride solution)
IEC 60068-2-54, Environmental testing – Part 2-54: Tests – Test Ta: Solderability testing of
electronic components by the wetting balance method
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 60068-2-69, Environmental testing – Part 2-69: Tests – Test Te: Solderability testing of
electronic components for surface mounting devices (SMD) by the wetting balance method
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 with axial terminations
IEC 61193-2, Quality assessment systems – Part 2: Selection and use of sampling plans for
inspection of electronic components and packages
IEC 60717, Method for the 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
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
type
group of products having similar design features manufactured by the same techniques and
falling within the manufacturer's usual range of ratings for these products
Note 1 to entry: Mounting accessories are ignored, provided they have no significant effect on the test results.
Note 2 to entry: Ratings cover the combination of
– electrical ratings,
– sizes, and
– climatic category.
Note 3 to entry: The limits of the range of ratings should be given in the detail specification.
3.2
style
variation within a type having specific nominal dimensions and characteristics

3.3
thermistor
thermally sensitive semiconducting resistor whose primary function is to exhibit an important
change in electrical resistance with a change in body temperature
3.4
negative temperature coefficient thermistor
NTC thermistor
thermistor in which the resistance decreases with increasing temperature
Note 1 to entry: In general, the term 'NTC thermistor' is used.
3.5
directly heated negative temperature coefficient thermistor
thermistor which obtains its resistance variation by the changes of physical conditions.
Note 1 to entry: Physical conditions include the current through the thermistor, ambient temperature, humidity,
wind velocity, gas, etc.
3.6
indirectly heated negative temperature coefficient thermistor
thermistor which obtains its resistance variation primarily by the change of temperature of the
thermistor, due to the change of a current through a separate heater which is in close contact
with, but electrically insulated from, the thermistor element
Note 1 to entry: The temperature of the thermistor can also be changed by the changes of physical conditions
such as current through the thermistor element itself, ambient temperature, humidity, wind velocity, gas, etc.
Note 2 to entry: This term is for information only.
3.7
positive temperature coefficient thermistor
PTC thermistor
thermistor in which the resistance increases with increasing temperature
Note 1 to entry: In general, the term 'PTC thermistor' is used.
Note 2 to entry: This term is for information only.
3.8
thermistor with wire terminations
thermistor provided with wire terminations
3.9
thermistor without wire terminations
thermistor provided only with two metallized faces, to be used as electrical contacts
Note 1 to entry: This term is for information only.
3.10
insulated thermistor
thermistor coated with materials such as resin, glass or ceramic, capable of meeting the
requirements of the insulation resistance and voltage proof tests when specified in the test
schedule
3.11
non-insulated thermistor
thermistor with or without coating materials for surfacing of elements but not intended to meet
the requirements of the insulation resistance and voltage proof tests when specified in the
test schedule
– 12 – IEC 60539-1:2016  IEC 2016
3.12
surface mount thermistor
thermistor whose small dimensions and nature or shape of terminations make it suitable for
use in hybrid circuits and on printed board
3.13
assembled thermistor
probe
thermistor encapsulated in different materials such as tubes, plastic and metal housing and/or
assembled with cables and/or connectors
Note 1 to entry: This term is for information only.
3.14
thermistor for sensing
thermistor which responds to temperature changes and therefore is used for temperature
sensing and control
3.15
inrush current limiting thermistor
thermistor which limits the inrush current just after switching on the power
3.16
residual resistance
value of the d.c. resistance of a thermistor when its
thermal stability is reached with the maximum current passing
Note 1 to entry: This term is for information only.
3.17
maximum permissible capacitance
maximum permissible capacitance value of a capacitor
which can be connected to a thermistor under loading
3.18
zero-power resistance
R
T
value of the d.c. resistance of a thermistor, when measured at a specified temperature, under
such conditions that the change in resistance due to the internal generation of heat is
negligible with respect to the total error of measurement
3.19
nominal zero-power resistance
nominal value of zero-power resistance at the standard reference temperature of 25 °C,
unless otherwise specified
3.20
resistance-temperature characteristic
relationship between the zero-power resistance and the body temperature of a thermistor
Note 1 to entry: Typical resistance-temperature characteristic for NTC thermistors is shown in Figure 1.

R
a
R
R
b
T T T T  (K)
a b
IEC
NOTE Slightly downward convexed curve when the temperat
...