IEC 60539-2:2019
(Main)Directly heated negative temperature coefficient thermistors - Part 2: Sectional specification - Surface mount negative temperature coefficient thermistors
Directly heated negative temperature coefficient thermistors - Part 2: Sectional specification - Surface mount negative temperature coefficient thermistors
IEC 60539-2:2019 is applicable to surface mount directly heated negative temperature coefficient thermistors, typically made from transition metal oxide materials with semiconducting properties. These thermistors have metallized connecting pads or soldering strips and are intended to be mounted directly on to substrates for hybrid circuits or on to printed boards.
This edition includes the following significant technical changes with respect to the previous edition:
a) revision for the structure in accordance with ISO/IEC Directives, Part 2:2016 (seventh edition) to the extent practicable, and for harmonizing with IEC 60539-1:2016;
b) the upper category temperatures of 175 °C, 200 °C, 250 °C, 315 °C, 400 °C in Table 1 have been added;
c) the dimensions of 0402M in Annex A have been added.
Thermistances à coefficient de température négatif à chauffage direct - Partie 2: Spécification intermédiaire - Thermistances à coefficient de température négatif pour montage en surface
L'IEC 60539-2:2019 s'applique aux thermistances à coefficient de température négatif à chauffage direct pour montage en surface, typiquement constituées de matériaux faits d'oxyde de métal de transition dotés de propriétés semi-conductrices. Ces thermistances sont équipées de contacts de connexion métallisés ou de bandes de brasure et sont destinées à être montées directement sur des substrats pour circuits hybrides ou sur des cartes imprimées.
La présente édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) révision de la structure conformément aux directives ISO/IEC, Partie 2:2016 (septième édition), dans la mesure du possible, et pour l'harmonisation avec l'IEC 60539-1:2016;
b) les températures maximales de catégorie 175 °C, 200 °C, 250 °C, 315 °C, 400 °C ont été ajoutées dans le Tableau 1;
c) les dimensions de 0402M à l'Annexe A ont été ajoutées.
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IEC 60539-2 ®
Edition 2.0 2019-07
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Directly heated negative temperature coefficient thermistors –
Part 2: Sectional specification – Surface mount negative temperature coefficient
thermistors
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IEC 60539-2 ®
Edition 2.0 2019-07
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Directly heated negative temperature coefficient thermistors –
Part 2: Sectional specification – Surface mount negative temperature coefficient
thermistors
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.040.30 ISBN 978-2-8322-7199-5
– 2 – IEC 60539-2:2019 RLV IEC 2019
CONTENTS
FOREWORD . 5
1 General .
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 Information to be given in a detail specification . 8
4.1 General . 8
4.2 Outline drawing and dimensions . 8
4.3 Mounting . 8
4.4 Ratings and characteristics . 8
4.4.1 Particular characteristics . 8
4.4.2 Marking . 8
Terminology .
5 Preferred ratings and characteristics . 9
5.1 Tolerances on rated zero-power resistance . 9
5.2 Climatic categories . 9
6 Quality assessment procedures . 9
Primary stage of manufacture .
Structurally similar components .
Qualification approval procedures .
The manufacturer shall comply with 3.4 of IEC 60539-1. .
Quality conformance inspection .
Qualification approval on the basis of the fixed sample size procedure .
Quality conformance inspection .
Formation of inspection lots .
Test schedule .
Delayed delivery .
Assessment level .
7 Test and measurement procedures . 13
7.1 Mounting . 13
7.2 Drying and recovery . 13
7.2.1 Drying . 13
7.2.2 Recovery . 13
7.3 Visual examination and check of dimensions . 13
7.3.1 Visual examination . 13
7.3.2 Requirements . 14
7.3.3 Marking . 15
7.3.4 Dimensions . 16
7.4 Electrical tests . 16
7.4.1 Zero-power resistance . 16
7.4.2 B-value or resistance ratio . 16
7.4.3 Resistance/temperature characteristic . 16
7.5 Thermal tests . 17
7.5.1 Dissipation factor (δ) . 17
7.5.2 Thermal time constant by cooling after self-heating (τ ) . 17
c
7.6 Resistance to soldering heat . 17
7.6.1 General . 17
7.6.2 Initial measurement . 17
7.6.3 Test conditions . 17
7.6.4 Recovery . 18
7.6.5 Final inspection, measurements and requirements. 18
7.7 Solderability . 18
7.7.1 General . 18
7.7.2 Test conditions . 18
7.7.3 Recovery . 19
7.7.4 Final inspection, measurements and requirements. 19
7.8 Rapid change of temperature . 19
7.9 Thermal shock . 19
Climatic sequence.
Initial measurements .
Dry heat .
Damp heat (cyclic), first cycle .
Cold.
Damp heat (cyclic), remaining cycles .
Final measurements .
7.10 Damp heat, steady state . 21
7.11 Endurance . 21
7.11.1 Endurance at T and P . 21
3 max
7.11.2 Endurance at upper category temperature . 22
7.12 Shear (adhesion) test . 22
7.13 Substrate bending test . 22
7.14 Component solvent resistance . 22
7.15 Solvent resistance of marking . 22
Annex A (normative) Guide for the specification and coding of dimensions of surface
mount negative temperature coefficient thermistors . 23
Annex B (normative) Quality assessment procedure . 25
B.1 Primary stage of manufacture . 25
B.2 Structurally similar components . 25
B.3 Qualification approval procedures . 25
B.4 Quality conformance inspection . 25
B.4.1 General . 25
B.4.2 Qualification approval on the basis of the fixed sample size procedure . 25
B.5 Quality conformance inspection . 27
B.5.1 Formation of inspection lots . 27
B.5.2 Test schedule . 28
B.5.3 Delayed delivery . 28
B.5.4 Assessment level . 28
Figure 1 – Fault: fissure or defect . 14
Figure 2 – Fault: crack . 14
Figure 3 – Separation or delamination . 14
Figure 4 – Exposed electrodes . 15
Figure 5 – Principal faces . 15
– 4 – IEC 60539-2:2019 RLV IEC 2019
Figure 6 – Principal terminations – Gull wing . 16
Figure 7 – Principal terminations – Round termination . 16
Figure A.1 – Dimensioning of surface mount thermistors . 23
Table 1 – Upper and lower category temperatures and duration of the damp heat test . 9
Table A.1 – Dimensions . 24
Table 2 B.1 – Fixed sample size test schedule for qualification approval of surface
mount negative temperature coefficient thermistors Assessment level EZ . 27
Table 3 B.2 – Lot-by-lot inspection . 29
Table 4 B.3 – Periodic test . 29
Table 5 – Number of cycles .
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DIRECTLY HEATED NEGATIVE TEMPERATURE
COEFFICIENT THERMISTORS –
Part 2: Sectional specification –
Surface mount negative temperature coefficient thermistors
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
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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.
This redline version of the official IEC Standard allows the user to identify the changes
made to the previous edition. A vertical bar appears in the margin wherever a change
has been made. Additions are in green text, deletions are in strikethrough red text.
– 6 – IEC 60539-2:2019 RLV IEC 2019
International Standard IEC 60539-2 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 2003 and Amendment
1:2010. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) revision for the structure in accordance with ISO/IEC Directives, Part 2:2016 (seventh
edition) to the extent practicable, and for harmonizing with IEC 60539-1:2016;
b) the upper category temperatures of 175 °C, 200 °C, 250 °C, 315 °C, 400 °C in Table 1
have been added;
c) the dimensions of 0402M in Annex A have been added.
The text of this International Standard is based on the following documents:
FDIS Report on voting
40/2672/FDIS 40/2680/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 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 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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
DIRECTLY HEATED NEGATIVE TEMPERATURE
COEFFICIENT THERMISTORS –
Part 2: Sectional specification –
Surface mount negative temperature coefficient thermistors
1 General
1 Scope
This part of IEC 60539 is applicable to surface mount directly heated negative temperature
coefficient thermistors, typically made from transition metal oxide materials with
semiconducting properties. These thermistors have metallized connecting pads or soldering
strips and are intended to be mounted directly on to substrates for hybrid circuits or on to
printed boards.
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 60068-2-2:19742007, Environmental testing – Part 2-2: Tests – Tests B: Dry heat
Amendment 1 (1993)
Amendment 2 (1994)
IEC 60068-2-14:19842009, Environmental testing – Part 2-14: Tests – Test N: Change of
temperature Amendment 1 (1986)
IEC 60068-2-30:1980, Environmental testing – Part 2: Tests – Test Db and guidance: Damp
heat, cyclic (12 + 12-hour cycle)
Amendment 1 (1985)
IEC 60068-2-58:19992015, 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 60068-2-58:2015/AMD1:2017
IEC 60068-2-78, Environmental testing – Part 2-78: Tests – Test Cab: Damp heat, steady
state
IEC 60410:1973, Sampling plans and procedures for inspection by attributes
IEC 60539-1:20022016, Directly heated negative temperature coefficient thermistors – Part 1:
Generic specification
IEC 61193-2:2007, Quality assessment systems – Part 2: Selection and use of sampling plans
for inspection of electronic components and packages
– 8 – IEC 60539-2:2019 RLV IEC 2019
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60539-1 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
4 Information to be given in a detail specification
4.1 General
Detail specifications shall be derived from the relevant blank detail specification.
Detail specifications shall not specify requirements inferior to those of the generic, sectional
or blank detail specification. When more severe requirements are included, they shall be
listed in 1.9 of the detail specification and indicated in the test schedules, for example, by an
asterisk.
NOTE The information given in 4.2 may for convenience, be presented in tabular form.
The information in 4.2 to 4.4 shall be given in each detail specification and the values quoted
shall preferably be selected from those given in the appropriate clause of this sectional
specification.
4.2 Outline drawing and dimensions
There shall be an illustration of the thermistor as an aid to easy recognition and for
comparison with others. Dimensions and their associated tolerances, which affect inter-
changeability and mounting, shall be given in the detail specification. All dimensions shall
preferably be stated in millimetres; however, when the original dimensions are given in inches,
the converted metric dimensions in millimetres shall be added.
Normally, the numerical values shall be given for the length, width and height of the body.
When necessary, for example when a number of items are covered by a detail specification,
the dimensions and their associated tolerances shall be placed in a table below the drawing.
When the configuration is other than described above, the detail specification shall state such
dimensional information as will adequately describe the thermistor.
4.3 Mounting
The detail specification shall give guidance on methods of mounting for normal use. Mounting
for test and measurement purposes (when required) shall be in accordance with 4.27 of
IEC 60539-1:2016, 5.4.
4.4 Ratings and characteristics
4.4.1 Particular characteristics
Additional characteristics may be listed when they are considered necessary to specify the
component adequately for design and application purposes.
4.4.2 Marking
See 2.4 of IEC 60539-1:2016, 4.3.
1.4 Terminology
See 2.2 of IEC 60539-1.
5 Preferred ratings and characteristics
5.1 Tolerances on rated zero-power resistance
Preferred values of tolerances on zero-power resistance are:
±0,5 %, ±1 %, ±2 %, ±3 %, ±5 %, ±10 %.
5.2 Climatic categories
The upper and lower category temperatures and the duration of the damp-heat steady-state
test shall be selected from Table 1.
Table 1 – Upper and lower category temperatures and duration of the damp heat test
Lower category temperature
−55, −40, −25, −10, −5, +5
ºC
Upper category temperature
70, 85, 100, 105, 125, 150, 155, 175, 200, 250, 315, 400
ºC
Damp heat, steady state
21, 42, 56
days
The detail specification shall prescribe the appropriate category.
6 Quality assessment procedures
3.1 Primary stage of manufacture
The primary stage of manufacture is defined as the initial mixing process of ingredients.
3.2 Structurally similar components
Surface mount thermistors may be grouped as structurally similar for the purpose of forming
inspection lots provided that the requirements of 3.1 of IEC 60539-1 are met, with the
following addition.
For the shear test and the substrate bending test, devices may be grouped if they have been
made on the same production line, have the same dimensions, internal structure and external
finish.
3.3 Qualification approval procedures
3.3.1 The manufacturer shall comply with 3.4 of IEC 60539-1.
3.4 Quality conformance inspection
Blank detail specifications associated with this specification shall prescribe the test schedule
for quality conformance inspection.
This schedule shall also specify the grouping, sampling and periodicity for the lot-by-lot and
periodic inspection.
– 10 – IEC 60539-2:2019 RLV IEC 2019
Inspection levels and sampling plans shall be selected from those given in IEC 60410.
If required, more then one test schedule may be specified.
3.4.1 Qualification approval on the basis of the fixed sample size procedure
a) Sampling
The sample shall be representative of the range of thermistors for which approval is sought.
This may or may not be the complete range covered by the detail specification.
The sample shall consist of specimens having the lowest, highest and middle-rated zero-
power resistance of each case size.
Per value, three spare specimens are permitted and may be used as replacements for
specimens which are defective because of incidents not attributable to the manufacturer.
b) Tests
The complete series of tests specified in Table 2 are required for the approval of thermistors
covered by one detail specification. The tests of each group shall be carried out in the order
given.
The whole sample shall be subjected to the tests of Group "0" and then divided for the other
groups.
Specimens found defective during the tests of Group "0" shall not be used for the other
groups.
"One defective" is counted when a thermistor has not satisfied the whole or a part of the tests
of a group.
Approval is granted when the number of non-conformances does not exceed the specified
number of permissible defects for each group or subgroup.
The conditions of test and performance requirements for the fixed sample size schedule shall
be identical to those described in the detail specification for quality conformance inspection.
Table 2 – Fixed sample size test schedule for qualification approval of surface mount
negative temperature coefficient thermistors
Assessment level EZ
a) b)
Group Test Subclause Conditions of test and n c
No. of this requirements
publication
0 Visual examination 4.3.1 See 4.3.1 to 4.3.2 90 0
Marking 4.3.3
Dimensions (gauging) 4.3.4 For requirements, see Table A.1
Zero-power resistance 4.4.1
1 Dimensions (detail) 4.3.4 For requirements, see Table A.1 10 0
B-value or resistance ratio 4.4.2 Choice to be made in the detail
specification
Resistance/temperature 4.4.3 Measuring temperatures to be
characteristic defined in the detail specification
Resistance to soldering heat – 4.6 See 4.6
dissolution of metallization
2 Solderability 4.7 See 4.7.1 to 4.7.3 10 0
Solvent resistance of marking 4.16
3 Resistance to soldering heat – 4.6 See 4.6.1 to 4.6.4 10 0
dewetting
4 Mounting 4.1 60 0
Visual examination 4.3.1
Zero-power resistance 4.4.1
4.1 Dissipation factor 4.5.1 10 0
Thermal time constant by cooling 4.5.2
after self-heating (τ )
c
4.2 Shear test 4.13 10 0
Rapid change of temperature 4.8
Climatic sequence 4.10
4.3 Damp heat, steady state 4.11 10 0
4.4 Endurance at θ and P 4.12.1 10 0
3 max
4.5 Endurance at upper category 4.12.2 10 0
temperature
5 Substrate bending test 4.14 10 0
a)
Number of specimens to be tested.
b)
Permissible numbers of non-conforming items.
3.5 Quality conformance inspection
3.5.1 Formation of inspection lots
a) Groups A and B inspection
These tests shall be carried out on a lot-by-lot basis.
A manufacturer may aggregate the current production into inspection lots subject to the
following safeguards:
a) the inspection lot shall consist of structurally similar thermistors (see 3.2);
– 12 – IEC 60539-2:2019 RLV IEC 2019
b) for Group A the sample tested shall consist of each of the values and each of the
dimensions contained in the inspection lot
– in relation to their number;
– with a minimum of five of any one value;
c) if there are less than five of any one value in the sample, the basis for the drawing of
samples shall be agreed upon between the manufacturer and the National Supervising
Inspectorate;
d) Group C inspection.
These tests shall be carried out on a periodic basis.
Samples shall be representative of the current production of the specified periods and shall
be divided into small, medium and large sizes. In order to cover the range of approvals in any
period, one rated zero-power resistance value shall be tested per group of sizes. In
subsequent periods, other sizes and rated zero-power values in production shall be tested
with the aim of covering the whole range.
3.5.2 Test schedule
The schedule for the lot-by-lot and periodic tests for quality conformance inspection is given
in Clause 2, Table 4 of the blank detail specification.
3.5.3 Delayed delivery
When, according to the procedures of 3.7 of IEC 60539-1, re-inspection has to be made,
solderability and zero-power resistance shall be checked as specified in Group A and Group B
inspection.
3.5.4 Assessment level
The assessment level(s) given in the blank detail specification shall preferably be selected
from Tables 3 and 4.
Table 3 – Lot-by-lot inspection
d) EZ
Inspection subgroup
a) a) a)
IL n c
b)
A0 100 %
c)
A1
S – 4 0
c)
A2
II 0
c)
B1
S – 3 0
c)
B2
S – 2 0
a)
IL = inspection level;
n = sample size;
c = permissible number of non-conforming items.
b)
100 % testing shall be followed by re-inspection by sampling in order to
monitor outgoing quality level by non-conforming items per million (ppm).
The sampling level shall be established by the manufacturer. For the
calculation of ppm values, any parametric failure shall be counted as a
non-conforming item. In case one or more non-conforming items occur in
a sample, this lot shall be rejected.
c)
Number to be tested: sample size as directly allotted to the code letter for
IL in Table IIA of IEC 60410 (single sampling plan for normal inspection).
d)
The content of the inspection subgroup is described in Clause 2 of the
relevant blank detail specification.
Table 4 – Periodic test
b) EZ
Inspection subgroup
a) a) a)
p n c
C1 3 12 0
C2 3 12 0
C3.1 6 27 0
C3.2 6 15 0
C3.3 3 15 0
b)
C3.4 6 15 0
C4 6 9 0
a)
p = periodicity in months;
n = sample size;
c = permissible number of non-conforming items.
b)
The content of the inspection subgroup is described in Clause 2 of the
relevant blank detail specification.
See Annex B.
7 Test and measurement procedures
7.1 Mounting
See 4.27 of IEC 60539-1:2016, 5.4.
7.2 Drying and recovery
7.2.1 Drying
Where drying is called for in this specification, the thermistor shall be conditioned as follows.
For 96 h ± 4 h in an oven at a temperature of 100 °C ± 5 °C, the thermistor shall then be
allowed to cool in a desiccator using a suitable desiccant, such as activated alumina or
silicagel, and shall be kept therein from the time of removal from the oven to the beginning of
the specified tests.
7.2.2 Recovery
Unless otherwise specified, recovery shall take place under the standard atmospheric
conditions for testing (see 4.2 of IEC 60539-1:2016, 5.3.2).
7.3 Visual examination and check of dimensions
7.3.1 Visual examination
Visual examination shall be carried out with suitable equipment with approximately 10×
magnification and lighting appropriate to the specimen under test and the quality level
required.
NOTE The operator should have facilities available for incident or transmitted illumination as
well as an appropriate measuring facility.
– 14 – IEC 60539-2:2019 RLV IEC 2019
7.3.2 Requirements
7.3.2.1 General
Quantitative values for the requirements below may be given in the detail or in the
manufacturer’s specification.
The thermistor shall conform to the following requirements.
7.3.2.2 Requirements for ceramic
Requirements for the ceramic are as follows:
1) Bulk type
a) It shall be free of fissures of coating glass longer than 25 % of dimension L (see
Annex A, Figure A.1) and defects of glass coating on each face greater than 10 % of
the area of that face (see Figure 1).
NOTE Fissure on a corner and defect on one side.
Figure 1 – Fault: fissure or defect
b) It shall be free of cracks, except for small damage on the surface, which does not
impair the performance of the thermistor (see Figure 2).
NOTE Crack on one side or extending from one face to another over a corner.
Figure 2 – Fault: crack
2) Layered type
a) It shall not exhibit visible separation or delamination between the layers of the
thermistor (see Figure 3). Excluding the case when a few things which do not influence
a characteristic of the surface implementation form an NTC thermistor, the surface
shall not be cracked (see Figure 3).
Figure 3 – Separation or delamination
b) It shall not exhibit exposed electrodes between the two terminations (see Figure 4).
It shall not exhibit any visible detachment of the metallized terminations nor any
exposed electrodes (see Figure 4).
Figure 4 – Exposed electrodes
7.3.2.3 Requirements for the metallization
Requirements for the metallization are as follows:
The principal faces are those noted A, B, C, D and E (see Figure 5).
In the case of thermistors of square section, faces D and E are also considered principal.
a) Termination on bottom is the principal face noted C.
b) Terminations on 3 sides are the principal faces noted A, B and C.
a) Terminations on 5 sides are the principal faces noted A, B, C, D and E.
Figure 5 – Principal faces
The maximum area of gaps in metallization on each principal face shall not be greater than
15 % of the area of that face; these gaps shall not be concentrated in the same area. The
gaps in metallization shall not affect the two principal edges of each extremity of the block (or
four edges for square thermistors). Dissolution of the end-face plating (leaching) shall not
exceed 25 % of the length of the edge concerned.
7.3.3 Marking
If there is marking on the body, it shall be legible as determined by visual examination.
a) Gull wing terminations are noted F in Figure 6.
– 16 – IEC 60539-2:2019 RLV IEC 2019
Figure 6 – Principal terminations – Gull wing
b) Round terminations are noted G in Figure 7.
Figure 7 – Principal terminations – Round termination
The names of the structures of termination are in accordance with IEC 62137-3:2011.
7.3.4 Dimensions
The dimensions indicated in the detail specification shall be checked and shall comply with
the values prescribed in Annex A.
7.4 Electrical tests
7.4.1 Zero-power resistance
See 4.5 of IEC 60539-1:2016, 5.6, with the following details.
The zero-power resistance shall be measured at the temperature given in the detail
specification and shall be within the limits specified in the detail specification, taking into
account the tolerance.
7.4.2 B-value or resistance ratio
See 4.6 of IEC 60539-1:2016, 5.7, with the following details:
– calculate the B-value or the resistance ratio using zero-power resistance values measured
at 25 °C and 85 °C, unless otherwise specified in the detail specification;
– the B-value or the resistance ratio shall be within the tolerance specified in the detail
specification.
7.4.3 Resistance/temperature characteristic
See 4.9 of IEC 60539-1:2016, 5.10, with the following details:
– the measuring temperature shall be selected from those given in IEC 60539-1:2016,
Table 1;
– the resistance/temperature characteristic shall be within the limits specified in the detail
specification.
7.5 Thermal tests
7.5.1 Dissipation factor (δ)
See 4.10 of IEC 60539-1:2016, 5.11, with the following details:
– thermistors shall be mounted in accordance with 7.1;
– the zero-power resistance shall be measured at the temperature T , which is equivalent to
b
85 °C ± 0,1 °C unless otherwise prescribed in the detail specification;
– the dissipation factor shall be within the limits specified in the detail specification.
7.5.2 Thermal time constant by cooling after self-heating (τ )
c
See 4.12 of IEC 60539-1:2016, 5.13, with the following details:
– the thermistors shall be mounted in accordance with 7.1;
– the thermal time constant by cooling after self-heating shall be within the limits prescribed
in the detail specification.
7.6 Resistance to soldering heat
7.6.1 General
See IEC 60068-2-58:2015 with the following details.
7.6.2 Initial measurement
The zero-power resistance shall be measured in accordance with 7.4.1.
7.6.3 Test conditions
7.6.3.1 Solder bath method
See IEC 60068-2-58, Clauses 5 and 6 with the following details, if not otherwise specified in
the detail specification:
– the specimen shall be preheated to a temperature of 110 °C to 140 °C and maintained for
30 s to 60 s;
– temperature: 260 °C ± 5 °C;
– duration of immersion: 10 s ± 1 s;
– depth of immersion: 10 mm;
– number of immersion: 1
See IEC 60068-2-58:2015, 7.5, unless otherwise specified in the detail specification.
4.6.2.2 Infrared and forced gas convection soldering system
See IEC 60068-2-58, Clauses 7 and 8 with the following details:
a) the solder paste shall be applied to the test substrate;
b) the thickness of the solder deposit shall be specified in the detail specification;
c) the terminations of the specimen shall be placed on solder paste;
d) the specimen and test substrate shall be preheated to a temperature of (150 ± 10) °C and
maintained for 60 s to 120 s in an infrared and forced gas convection soldering system;
– 18 – IEC 60539-2:2019 RLV IEC 2019
e) the temperature of the reflow system shall be quickly raised until the specimen has
reached (235 ± 5) °C and maintained at this temperature for (10 ± 1) s. Number of tests: 2;
f) the temperature profile shall be specified in the detail specification.
7.6.3.2 Reflow method
See IEC 60068-2-58:2015, 7.6, unless otherwise specified in the detail specification.
7.6.4 Recovery
The flux residues shall be removed with a suitable solvent.
7.6.5 Final inspection, measurements and requirements
After recovery, the surface mount thermistors shall be visually examined and measured and
shall meet the following requirements.
Visual examination shall be specified in the detail specification with the following details:
– under normal lighting and approximately 10× magnification, there shall be no signs of
damage such as cracks;
– dissolution of the end-face plating (leaching) shall not exceed 25 % of the length of the
edge concerned.
The zero-power resistance shall be measured in accordance with 7.4.1 and the change shall
not exceed ±5 %.
7.7 Solderability
7.7.1 General
See IEC 60068-2-58 with the following details:
7.7.2 Test conditions
7.7.2.1 Solder bath method
See IEC 60068-2-58, Clauses 5 and 6 with the following details, if not otherwise specified in
the detail specification:
– the specimen shall be preheated to a temperature of 80 °C to 140 °C and maintained for
30 s to 60 s;
– temperature: 235 °C ± 5 °C;
– duration of immersion: 2 s ± 0,2 s;
– depth of immersion: 10 mm;
– number of immersion: 1
See IEC 60068-2-58:2015 and IEC 60068-2-58:2015/AMD1:2017, 6.5, unless otherwise
specified in the detail specification.
4.7.1.2 Infrared and forced gas convection soldering system
See IEC 60068-2-58, Clauses 7 and 8 with the following details:
a) the solder paste shall be applied to the test substrate;
b) the thickness of the solder deposit shall be specified in the detail specification;
c) the terminations of the specimen shall be placed on solder paste;
d) unless otherwise specified in the detail specification, the specimen and test substrate shall
be preheated to a temperature of (150 ± 10) °C and maintained for 60 s to 120 s in
infrared and forced gas convection soldering system;
e) the temperature of reflow system shall be quickly raised until the specimen has reached
(215 ± 3) °C and maintained at this temperature for (10 ± 1) s;
f) the temperature profile shall be specified in the detail specification.
7.7.2.2 Reflow method
See IEC 60068-2-58:2015, 6.6, unless otherwise specified in the detail specification.
7.7.3 Recovery
The flux residues shall be removed with a suitable solvent.
7.7.4 Final inspection, measurements and requireme
...
IEC 60539-2 ®
Edition 2.0 2019-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Directly heated negative temperature coefficient thermistors –
Part 2: Sectional specification – Surface mount negative temperature coefficient
thermistors
Thermistances à coefficient de température négatif à chauffage direct –
Partie 2: Spécification intermédiaire – Thermistances à coefficient de
température négatif pour montage en surface
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IEC 60539-2 ®
Edition 2.0 2019-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Directly heated negative temperature coefficient thermistors –
Part 2: Sectional specification – Surface mount negative temperature coefficient
thermistors
Thermistances à coefficient de température négatif à chauffage direct –
Partie 2: Spécification intermédiaire – Thermistances à coefficient de
température négatif pour montage en surface
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.040.30 ISBN 978-2-8322-7098-1
– 2 – IEC 60539-2:2019 IEC 2019
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Information to be given in a detail specification . 7
4.1 General . 7
4.2 Outline drawing and dimensions . 7
4.3 Mounting . 7
4.4 Ratings and characteristics . 7
4.4.1 Particular characteristics . 7
4.4.2 Marking . 7
5 Preferred ratings and characteristics . 7
5.1 Tolerances on rated zero-power resistance . 7
5.2 Climatic categories . 8
6 Quality assessment procedures . 8
7 Test and measurement procedures . 8
7.1 Mounting . 8
7.2 Drying and recovery . 8
7.2.1 Drying . 8
7.2.2 Recovery . 8
7.3 Visual examination and check of dimensions . 8
7.3.1 Visual examination . 8
7.3.2 Requirements . 9
7.3.3 Marking . 10
7.3.4 Dimensions . 11
7.4 Electrical tests . 11
7.4.1 Zero-power resistance . 11
7.4.2 B-value or resistance ratio . 11
7.4.3 Resistance/temperature characteristic . 11
7.5 Thermal tests . 12
7.5.1 Dissipation factor (δ) . 12
7.5.2 Thermal time constant by cooling after self-heating (τ ) . 12
c
7.6 Resistance to soldering heat . 12
7.6.1 General . 12
7.6.2 Initial measurement . 12
7.6.3 Test conditions . 12
7.6.4 Recovery . 12
7.6.5 Final inspection, measurements and requirements. 12
7.7 Solderability . 13
7.7.1 General . 13
7.7.2 Test conditions . 13
7.7.3 Recovery . 13
7.7.4 Final inspection, measurements and requirements. 13
7.8 Rapid change of temperature . 13
7.9 Thermal shock . 13
7.10 Damp heat, steady state . 14
7.11 Endurance . 14
7.11.1 Endurance at T and P . 14
3 max
7.11.2 Endurance at upper category temperature . 15
7.12 Shear (adhesion) test . 15
7.13 Substrate bending test . 15
7.14 Component solvent resistance . 15
7.15 Solvent resistance of marking . 15
Annex A (normative) Guide for the specification and coding of dimensions of surface
mount negative temperature coefficient thermistors . 16
Annex B (normative) Quality assessment procedure . 17
B.1 Primary stage of manufacture . 17
B.2 Structurally similar components . 17
B.3 Qualification approval procedures . 17
B.4 Quality conformance inspection . 17
B.4.1 General . 17
B.4.2 Qualification approval on the basis of the fixed sample size procedure . 17
B.5 Quality conformance inspection . 19
B.5.1 Formation of inspection lots . 19
B.5.2 Test schedule . 20
B.5.3 Delayed delivery . 20
B.5.4 Assessment level . 20
Figure 1 – Fault: fissure or defect . 9
Figure 2 – Fault: crack . 9
Figure 3 – Separation or delamination . 9
Figure 4 – Exposed electrodes . 10
Figure 5 – Principal faces . 10
Figure 6 – Principal terminations – Gull wing . 11
Figure 7 – Principal terminations – Round termination . 11
Figure A.1 – Dimensioning of surface mount thermistors . 16
Table 1 – Upper and lower category temperatures and duration of the damp heat test . 8
Table A.1 – Dimensions . 16
Table B.1 – Fixed sample size test schedule for qualification approval of surface mount
negative temperature coefficient thermistors Assessment level EZ . 19
Table B.2 – Lot-by-lot inspection . 20
Table B.3 – Periodic test . 21
– 4 – IEC 60539-2:2019 IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DIRECTLY HEATED NEGATIVE TEMPERATURE
COEFFICIENT THERMISTORS –
Part 2: Sectional specification –
Surface mount negative temperature coefficient thermistors
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 60539-2 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 2003 and Amendment
1:2010. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) revision for the structure in accordance with ISO/IEC Directives, Part 2:2016 (seventh
edition) to the extent practicable, and for harmonizing with IEC 60539-1:2016;
b) the upper category temperatures of 175 °C, 200 °C, 250 °C, 315 °C, 400 °C in Table 1
have been added;
c) the dimensions of 0402M in Annex A have been added.
The text of this International Standard is based on the following documents:
FDIS Report on voting
40/2672/FDIS 40/2680/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 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 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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – IEC 60539-2:2019 IEC 2019
DIRECTLY HEATED NEGATIVE TEMPERATURE
COEFFICIENT THERMISTORS –
Part 2: Sectional specification –
Surface mount negative temperature coefficient thermistors
1 Scope
This part of IEC 60539 is applicable to surface mount directly heated negative temperature
coefficient thermistors, typically made from transition metal oxide materials with
semiconducting properties. These thermistors have metallized connecting pads or soldering
strips and are intended to be mounted directly on to substrates for hybrid circuits or on to
printed boards.
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 60068-2-2:2007, Environmental testing – Part 2-2: Tests – Tests B: Dry heat
IEC 60068-2-14:2009, Environmental testing – Part 2-14: Tests – Test N: Change of
temperature
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 60068-2-58:2015/AMD1:2017
IEC 60068-2-78, Environmental testing – Part 2-78: Tests – Test Cab: Damp heat, steady
state
IEC 60539-1:2016, Directly heated negative temperature coefficient thermistors – Part 1:
Generic specification
IEC 61193-2:2007, Quality assessment systems – Part 2: Selection and use of sampling plans
for inspection of electronic components and packages
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60539-1 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
4 Information to be given in a detail specification
4.1 General
Detail specifications shall be derived from the relevant blank detail specification.
Detail specifications shall not specify requirements inferior to those of the generic, sectional
or blank detail specification. When more severe requirements are included, they shall be
listed in 1.9 of the detail specification and indicated in the test schedules, for example, by an
asterisk.
The information given in 4.2 may for convenience, be presented in tabular form.
The information in 4.2 to 4.4 shall be given in each detail specification and the values quoted
shall preferably be selected from those given in the appropriate clause of this sectional
specification.
4.2 Outline drawing and dimensions
There shall be an illustration of the thermistor as an aid to easy recognition and for
comparison with others. Dimensions and their associated tolerances, which affect inter-
changeability and mounting, shall be given in the detail specification. All dimensions shall
preferably be stated in millimetres; however, when the original dimensions are given in inches,
the converted metric dimensions in millimetres shall be added.
Normally, the numerical values shall be given for the length, width and height of the body.
When necessary, for example when a number of items are covered by a detail specification,
the dimensions and their associated tolerances shall be placed in a table below the drawing.
When the configuration is other than described above, the detail specification shall state such
dimensional information as will adequately describe the thermistor.
4.3 Mounting
The detail specification shall give guidance on methods of mounting for normal use. Mounting
for test and measurement purposes (when required) shall be in accordance with
IEC 60539-1:2016, 5.4.
4.4 Ratings and characteristics
4.4.1 Particular characteristics
Additional characteristics may be listed when they are considered necessary to specify the
component adequately for design and application purposes.
4.4.2 Marking
See IEC 60539-1:2016, 4.3.
5 Preferred ratings and characteristics
5.1 Tolerances on rated zero-power resistance
Preferred values of tolerances on zero-power resistance are:
±0,5 %, ±1 %, ±2 %, ±3 %, ±5 %, ±10 %.
– 8 – IEC 60539-2:2019 IEC 2019
5.2 Climatic categories
The upper and lower category temperatures and the duration of the damp-heat steady-state
test shall be selected from Table 1.
Table 1 – Upper and lower category temperatures and duration of the damp heat test
Lower category temperature
−55, −40, −25, −10, −5, +5
ºC
Upper category temperature
70, 85, 100, 105, 125, 150, 155, 175, 200, 250, 315, 400
ºC
Damp heat, steady state
21, 42, 56
days
The detail specification shall prescribe the appropriate category.
6 Quality assessment procedures
See Annex B.
7 Test and measurement procedures
7.1 Mounting
See IEC 60539-1:2016, 5.4.
7.2 Drying and recovery
7.2.1 Drying
Where drying is called for in this specification, the thermistor shall be conditioned as follows.
For 96 h ± 4 h in an oven at a temperature of 100 °C ± 5 °C, the thermistor shall then be
allowed to cool in a desiccator using a suitable desiccant, such as activated alumina or
silicagel, and shall be kept therein from the time of removal from the oven to the beginning of
the specified tests.
7.2.2 Recovery
Unless otherwise specified, recovery shall take place under the standard atmospheric
conditions for testing (see IEC 60539-1:2016, 5.3.2).
7.3 Visual examination and check of dimensions
7.3.1 Visual examination
Visual examination shall be carried out with suitable equipment with approximately 10×
magnification and lighting appropriate to the specimen under test and the quality level
required.
The operator should have facilities available for incident or transmitted illumination as well as
an appropriate measuring facility.
7.3.2 Requirements
7.3.2.1 General
Quantitative values for the requirements below may be given in the detail or in the
manufacturer’s specification.
The thermistor shall conform to the following requirements.
7.3.2.2 Requirements for ceramic
Requirements for the ceramic are as follows:
1) Bulk type
a) It shall be free of fissures of coating glass longer than 25 % of dimension L (see
Annex A, Figure A.1) and defects of glass coating on each face greater than 10 % of
the area of that face (see Figure 1).
NOTE Fissure on a corner and defect on one side.
Figure 1 – Fault: fissure or defect
b) It shall be free of cracks, except for small damage on the surface, which does not
impair the performance of the thermistor (see Figure 2).
NOTE Crack on one side or extending from one face to another over a corner.
Figure 2 – Fault: crack
2) Layered type
a) It shall not exhibit visible separation or delamination between the layers of the
thermistor (see Figure 3). Excluding the case when a few things which do not influence
a characteristic of the surface implementation form an NTC thermistor, the surface
shall not be cracked (see Figure 3).
Figure 3 – Separation or delamination
b) It shall not exhibit exposed electrodes between the two terminations (see Figure 4).
It shall not exhibit any visible detachment of the metallized terminations nor any
exposed electrodes (see Figure 4).
– 10 – IEC 60539-2:2019 IEC 2019
Figure 4 – Exposed electrodes
7.3.2.3 Requirements for the metallization
Requirements for the metallization are as follows:
The principal faces are those noted A, B, C, D and E (see Figure 5).
a) Termination on bottom is the principal face noted C.
b) Terminations on 3 sides are the principal faces noted A, B and C.
c) Terminations on 5 sides are the principal faces noted A, B, C, D and E.
Figure 5 – Principal faces
The maximum area of gaps in metallization on each principal face shall not be greater than
15 % of the area of that face; these gaps shall not be concentrated in the same area. The
gaps in metallization shall not affect the two principal edges of each extremity of the block (or
four edges for square thermistors). Dissolution of the end-face plating (leaching) shall not
exceed 25 % of the length of the edge concerned.
7.3.3 Marking
If there is marking on the body, it shall be legible as determined by visual examination.
a) Gull wing terminations are noted F in Figure 6.
Figure 6 – Principal terminations – Gull wing
b) Round terminations are noted G in Figure 7.
Figure 7 – Principal terminations – Round termination
The names of the structures of termination are in accordance with IEC 62137-3:2011.
7.3.4 Dimensions
The dimensions indicated in the detail specification shall be checked and shall comply with
the values prescribed in Annex A.
7.4 Electrical tests
7.4.1 Zero-power resistance
See IEC 60539-1:2016, 5.6, with the following details.
The zero-power resistance shall be measured at the temperature given in the detail
specification and shall be within the limits specified in the detail specification, taking into
account the tolerance.
7.4.2 B-value or resistance ratio
See IEC 60539-1:2016, 5.7, with the following details:
– calculate the B-value or the resistance ratio using zero-power resistance values measured
at 25 °C and 85 °C, unless otherwise specified in the detail specification;
– the B-value or the resistance ratio shall be within the tolerance specified in the detail
specification.
7.4.3 Resistance/temperature characteristic
See IEC 60539-1:2016, 5.10, with the following details:
– the measuring temperature shall be selected from those given in IEC 60539-1:2016,
Table 1;
– 12 – IEC 60539-2:2019 IEC 2019
– the resistance/temperature characteristic shall be within the limits specified in the detail
specification.
7.5 Thermal tests
7.5.1 Dissipation factor (δ)
See IEC 60539-1:2016, 5.11, with the following details:
– thermistors shall be mounted in accordance with 7.1;
– the zero-power resistance shall be measured at the temperature T , which is equivalent to
b
85 °C ± 0,1 °C unless otherwise prescribed in the detail specification;
– the dissipation factor shall be within the limits specified in the detail specification.
7.5.2 Thermal time constant by cooling after self-heating (τ )
c
See IEC 60539-1:2016, 5.13, with the following details:
– the thermistors shall be mounted in accordance with 7.1;
– the thermal time constant by cooling after self-heating shall be within the limits prescribed
in the detail specification.
7.6 Resistance to soldering heat
7.6.1 General
See IEC 60068-2-58:2015 with the following details.
7.6.2 Initial measurement
The zero-power resistance shall be measured in accordance with 7.4.1.
7.6.3 Test conditions
7.6.3.1 Solder bath method
See IEC 60068-2-58:2015, 7.5, unless otherwise specified in the detail specification.
7.6.3.2 Reflow method
See IEC 60068-2-58:2015, 7.6, unless otherwise specified in the detail specification.
7.6.4 Recovery
The flux residues shall be removed with a suitable solvent.
7.6.5 Final inspection, measurements and requirements
After recovery, the surface mount thermistors shall be visually examined and measured and
shall meet the following requirements.
Visual examination shall be specified in the detail specification with the following details:
– under normal lighting and approximately 10× magnification, there shall be no signs of
damage such as cracks;
– dissolution of the end-face plating (leaching) shall not exceed 25 % of the length of the
edge concerned.
The zero-power resistance shall be measured in accordance with 7.4.1 and the change shall
not exceed ±5 %.
7.7 Solderability
7.7.1 General
See IEC 60068-2-58 with the following details:
7.7.2 Test conditions
7.7.2.1 Solder bath method
See IEC 60068-2-58:2015 and IEC 60068-2-58:2015/AMD1:2017, 6.5, unless otherwise
specified in the detail specification.
7.7.2.2 Reflow method
See IEC 60068-2-58:2015, 6.6, unless otherwise specified in the detail specification.
7.7.3 Recovery
The flux residues shall be removed with a suitable solvent.
7.7.4 Final inspection, measurements and requirements
See the detail specification with the following details:
– the surface mount thermistors shall be visually examined under normal lighting and
approximately 10× magnification and there shall be no signs of damage;
– both the end face and the contact areas shall be covered with a smooth and bright solder
coating with no more than a small amount of scattered imperfections such as pinholes or
un-wetted or de-wetted areas. These imperfections shall not be concentrated in one area.
7.8 Rapid change of temperature
See IEC 60539-1:2016, 5.17.
The thermistors shall be mounted in accordance with 7.1.
The zero-power resistance shall be measured in accordance with 7.4.1.
The test shall be carried out in accordance with IEC 60068-2-14, Test Na with the following
conditions:
1) the lower temperature T shall be the lower category temperature;
A
2) the higher temperature T shall be the upper category temperature;
B
3) the number of cycles shall be 5;
4) the medium of the test chamber is air.
The thermistors shall be visually examined and the zero-power resistance shall be measured.
Under normal lighting and approximately 10× magnification, there shall be no signs of damage
such as cracks.
The zero-power resistance change shall not exceed ±5 %.
7.9 Thermal shock
See IEC 60539-1:2016, 5.21, with the following details:
– 14 – IEC 60539-2:2019 IEC 2019
– the thermistors shall be mounted in accordance with 7.1;
– the zero-power resistance shall be measured in accordance with 7.4.1.
The test shall be carried out according to IEC 60068-2-14, Test Nc with the following details:
1) the lower temperature T shall be the lower category temperature;
A
2) the higher temperature T shall be the upper category temperature;
B
3) the exposure time t1 shall be 30 min;
4) the number of cycles shall be 5;
5) the medium of the test bath shall be oil.
The thermistors shall be visually examined and the zero-power resistance shall be measured.
Under normal lighting and approximately 10× magnification, there shall be no signs of damage
such as cracks.
The zero-power resistance change shall not exceed ±5 %.
7.10 Damp heat, steady state
See IEC 60539-1:2016, 5.24.
The thermistors shall be mounted in accordance with 7.1.
The zero-power resistance shall be measured in accordance with 7.4.1.
The thermistors shall be subjected to Test Cab of IEC 60068-2-78 using the severity
corresponding to the climatic category of the thermistor as given in the detail specification.
At the end of the test, the thermistors shall be removed from the chamber and shall then be
subjected to recovery in accordance with 7.3.2.
The thermistors shall be visually examined, and the zero-power resistance shall be measured.
Under normal lighting and approximately 10× magnification, there shall be no signs of damage
such as cracks. The zero-power resistance change shall not exceed ±5 %.
7.11 Endurance
7.11.1 Endurance at T and P
3 max
See IEC 60539-1:2016, 5.25.4, with the following details:
– the thermistors shall be mounted in accordance with 7.1;
– the zero-power resistance shall be measured in accordance with 7.4.1;
– the thermistors shall be placed in a test chamber and subjected to the temperature
T ± 2 °C for 42 days (1 000 h) and at dissipation P ;
3 max
– after 168 h and 500 h, the thermistors shall be removed from the chamber and allowed to
recover under standard atmospheric conditions of testing for not less than 1 h and not
more than 2 h;
– the zero-power resistance shall be measured, and its change shall not exceed ±5 %;
– after intermediate measurements, the thermistors shall be returned to the test conditions.
The interval between the removal from, and the return to, the test conditions for any
thermistor shall not exceed 12 h;
– after 1 000 h ± 48 h, the thermistors shall be removed and allowed to recover under
standard atmospheric conditions for a period of 1 h to 2 h;
– the thermistors shall be visually examined, and the zero-power resistance shall be
measured. Under normal lighting and approximately 10× magnification, there shall be no
signs of damage such as cracks. The zero-power resistance change shall not exceed ±5 %.
7.11.2 Endurance at upper category temperature
See IEC 60539-1:2016, 5.25, with the following details:
– the thermistors shall be mounted in accordance with 7.1;
– the zero-power resistance shall be measured in accordance with 7.4.1;
– the thermistors shall be placed in a test chamber and subjected to the upper category
temperature ±2 °C and zero dissipation for 1 000 h. The chamber shall meet the
requirements of that specified for Test Ba of IEC 60068-2-2;
– after 168 h and 500 h, the thermistors shall be removed from the chamber and allowed to
recover under standard atmospheric conditions of testing for not less than 1 h and not
more than 2 h;
– the zero-power resistance shall be measured, and its change shall not exceed ±5 %;
– after intermediate measurements, the thermistors shall be returned to the test conditions.
The interval between the removal from, and the return to, the test conditions for any
thermistor shall not exceed 12 h;
– after 1 000 h ± 48 h, the thermistors shall be removed and allowed to recover under
standard atmospheric conditions for a period of 1 h to 2 h;
– the thermistors shall be visually examined, and the zero-power resistance shall be measured.
Under normal lighting and approximately 10× magnification, there shall be no signs of damage
such as cracks. The zero-power resistance change shall not exceed ±5 %.
7.12 Shear (adhesion) test
See IEC 60539-1:2016, 5.26.
7.13 Substrate bending test
See IEC 60539-1:2016, 5.27, with the following details:
– deflection D and the number of bends shall be specified in the detail specification;
– the zero-power resistance change shall not exceed ±5 %.
7.14 Component solvent resistance
See IEC 60539-1:2016, 5.28, with the following details:
– before and after the test, the zero-power resistance shall be measured.
– the thermistors shall be visually examined, and the zero-power resistance shall be
measured. Under normal lighting and approximately 10× magnification, there shall be no
signs of damage such as cracks. The zero-power resistance change shall not exceed ±5 %.
7.15 Solvent resistance of marking
See IEC 60539-1:2016, 5.29.
– 16 – IEC 60539-2:2019 IEC 2019
Annex A
(normative)
Guide for the specification and coding of dimensions
of surface mount negative temperature coefficient thermistors
The following principles should be considered in the dimensioning of surface mount negative
temperature coefficient thermistors.
Dimension W should not exceed dimension L .
Dimension H should not exceed dimension W.
If necessary, the thickness of tinning should be specified.
Figure A.1 – Dimensioning of surface mount thermistors
Table A.1 – Dimensions
Dimension in millimetres
Code Length Width L and L L
2 3 4
L W Minimum Minimum
0402 M 0,4 ± 0,05 0,2 ± 0,05 0,05 0,10
0603 M 0,1 0,15
0,6 ± 0,05 0,3 ± 0,05
1005 M 0,1 0,25
1,0 ± 0,15 0,5 ± 0,15
1608 M 1,6 ± 0,15 0,8 ± 0,15 0,2 0,35
2012 M 0,2 0,50
2,0 ± 0,2 1,25 ± 0,2
3216 M 0,3 1,4
3,2 ± 0,2 1,6 ± 0,2
3225 M 3,2 ± 0,2 2,5 ± 0,3 0,4 1,4
Other case sizes and dimensions may be specified in the detail specification.
Annex B
(normative)
Quality assessment procedure
B.1 Primary stage of manufacture
The primary stage of manufacture is defined as the initial mixing process of ingredients.
B.2 Structurally similar components
Surface mount thermistors may be grouped as structurally similar for the purpose of forming
inspection lots provided that the requirements of IEC 60539-1:2016, Q.1, are met, with the
following addition.
For the shear test and the substrate bending test, devices may be grouped if they have been
made on the same production line, have the same dimensions, internal structure and external
finish.
B.3 Qualification approval procedures
The manufacturer shall comply with IEC 60539-1:2016, Q.4.
B.4 Quality conformance inspection
B.4.1 General
Blank detail specifications associated with this specification shall prescribe the test schedule
for quality conformance inspection.
This schedule shall also specify the grouping, sampling and periodicity for the lot-by-lot and
periodic inspection.
Inspection levels and sampling plans shall be selected from those given in IEC 61193-2.
If required, more than one test schedule may be specified.
B.4.2 Qualification approval on the basis of the fixed sample size procedure
B.4.2.1 Sampling
The sample shall be representative of the range of thermistors for which approval is sought.
This may or may not be the complete range covered by the detail specification.
The sample shall consist of specimens having the lowest, highest and middle-rated zero-
power resistance of each case size.
Per value, three spare specimens are permitted and may be used as replacements for
specimens that are defective because of incidents not attributable to the manufacturer.
– 18 – IEC 60539-2:2019 IEC 2019
B.4.2.2 Tests
The complete series of tests specified in Table B.1 are required for the approval of
thermistors covered by one detail specification. The tests of each group shall be carried out in
the order given.
The whole sample shall be subjected to the tests of Group "0" and then divided for the other
groups.
Specimens found to be defective during the tests of Group "0" shall not be used for the other
groups.
One "defective" is counted when a thermistor has not satisfied the whole or a part of the tests
of a group.
Approval is granted when the number of non-conformances does not exceed the specified
number of permissible defects for each group or subgroup.
The conditions of test and performance requirements for the fixed sample size schedule shall
be identical to those des
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