IEC TR 61189-3-914:2017

IEC TR 61189-3-914 ®
Edition 1.0 2017-03
TECHNICAL
REPORT
colour
inside
Test methods for electrical materials, printed boards and other interconnection
structures and assemblies –
Part 3-914: Test method for thermal conductivity of printed circuit boards for
high-brightness LEDs – Guidelines

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IEC TR 61189-3-914 ®
Edition 1.0 2017-03
TECHNICAL
REPORT
colour
inside
Test methods for electrical materials, printed boards and other interconnection

structures and assemblies –
Part 3-914: Test method for thermal conductivity of printed circuit boards for

high-brightness LEDs – Guidelines

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.180 ISBN 978-2-8322-4110-3

– 2 – IEC TR 61189-3-914:2017 © IEC 2017
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Test condition . 7
4.1 Standard condition . 7
4.2 Specified condition . 8
5 Pre-condition . 8
6 Heat dissipation characteristics . 8
6.1 General . 8
6.2 Measurement of thermal resistance on the plane . 9
6.3 Thermal resistance across the thickness . 12
6.4 Thermal resistance measurement procedures and precautions . 14
6.4.1 General . 14
6.4.2 Die attach . 14
6.4.3 Wire bonding . 14
6.4.4 Temperature measuring sensor (calibration) . 14
6.4.5 Measurement of thermal resistance on the plane . 14
6.4.6 Thermal resistance across the thickness using cold plate . 16
Annex A (informative) Classification and class of the PCB . 19
Annex B (informative) Measurement comparison between companies (plane) . 22

Figure 1 – Example of PCB with large thermal conductivity . 9
Figure 2 – Examples of PCBs with large heat transfer coefficients . 9
Figure 3 – Illustration of thermal resistance test (for information) . 10
Figure 4 – Layout of the specimen surface for the thermal resistance test . 11
Figure 5 –Test equipment for thermal resistance across the thickness . 12
Figure 6 – Example of attachment of the specimen . 15
Figure 7 – Example of measurement of the thermal resistance on the plane . 16
Figure 8 – Use of the silicone grease . 17
Figure 9 – Test equipment for thermal resistance across the thickness (running water
tank specification) . 17
Figure 10 – Test equipment for thermal resistance across the thickness (cold plate) . 17
Figure A.1 – Example of classification and their application by base materials, PCBs
and final products . 20
Figure A.2 – The relation between thermal conductive parameter (W/(mK)) and heat
transfer coefficient parameter (mapping by substrate) . 21

Table 1 – Load heat (W) corresponding to range of thermal resistance on the plane
(K/W) . 12
Table 2 – Load heat (W) corresponding to range of thermal resistance to the direction
of the thickness (K/W) . 13

Table A.1 – Application and classification . 19
Table A.2 – The relation between thermal conductive parameter (W/(mK)) and heat
transfer coefficient parameter (mapping by zone) . 21

– 4 – IEC TR 61189-3-914:2017 © IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
TEST METHODS FOR ELECTRICAL MATERIALS, PRINTED BOARDS
AND OTHER INTERCONNECTION STRUCTURES AND ASSEMBLIES –

Part 3-914: Test method for thermal conductivity of printed
circuit boards for high-brightness LEDs – Guidelines

FOREWORD
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The main task of IEC technical committees is to prepare International Standards. However, a
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example "state of the art".
IEC TR 61189-3-914, which is a technical report, has been prepared by IEC technical
committee 91: Electronics assembly technology.

The text of this technical report is based on the following documents:
Enquiry draft Report on voting
91/1378/DTR 91/1403/RVC
Full information on the voting for the approval of this technical report 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 61189 series, published under the general title Test methods for
electrical materials, printed boards and other interconnection structures and assemblies, 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.
A bilingual version of this publication may be issued at a later date.

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– 6 – IEC TR 61189-3-914:2017 © IEC 2017
INTRODUCTION
Development of this technical report has been discussed at TC 91 Plenary meeting in
Dongguan, China, October 30, 2015 as per 91/1343A/RM dated on January 22, 2016.
This document was developed as a supplementary document to the IEC 61189-3-913.
Therefore, this document has been developed as technical report.
This document is given for information only.

TEST METHODS FOR ELECTRICAL MATERIALS, PRINTED BOARDS
AND OTHER INTERCONNECTION STRUCTURES AND ASSEMBLIES –

Part 3-914: Test method for thermal conductivity of printed
circuit boards for high-brightness LEDs – Guidelines

1 Scope
This document specifies the detailed procedures and precautions for IEC 61189-3-913.
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 60194, Printed board design, manufacture and assembly – Terms and definitions
IEC 60068-1:2013, Environmental testing – Part 1: General and guidance
IEC 61189-3-913, Test methods for electrical materials, printed boards and other
interconnection structures and assemblies – Part 3-913: Test method for thermal conductivity
of electronic circuit boards for high-brightness LEDs
EIA/JEDEC STD 51-2, Integrated circuits thermal test method – Environmental conditions –
Natural convection (still air)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60194 apply, unless
otherwise specified.
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 Test condition
4.1 Standard condition
Unless otherwise specified, tests should all be operated under the following standardized
conditions in accordance with the IEC 60068-1:2013, Clause 4:
• temperature: 15 °C to 35 °C;
• relative humidity: 25 % to 75 %;
• atmospheric pressure: 86 kPa to 106 kPa.

– 8 – IEC TR 61189-3-914:2017 © IEC 2017
If there is any doubt concerning the testing results under standardized condition, or upon a
request to check the atmospheric condition, the re-examination should be operated under
atmosphere in accordance with IEC 60068-1:2013.
If the standardized atmosphere is difficult to provide, testing under non-standardized
atmosphere is acceptable as long as the atmospheric condition does not affect the testing
results.
4.2 Specified condition
The specified condition should be in accordance with the condition specified in IEC 60068-
1:2013, Clause 4:
• temperature: 20 °C ± 2 °C;
• relative humidity: 60 % to 70 %;
• atmospheric pressure: 86 kPa to 106 kPa.
5 Pre-condition
Pre-conditioning should be in accordance with a) or b) below:
a) leave the specimen for 24 h in the standard condition;
b) leave the specimen for 60 min in a thermostat chamber at 85 °C ± 2 °C and then leave the
specimen for 24 h ± 4 h in the standard atmospheric condition.
NOTE This test element group (hereafter, referred to as TEG) chip includes a heater with a temperature
measuring sensor. In this document, the TEG chip indicates a chip with a temperature measuring sensor.
6 Heat dissipation characteristics
6.1 General
For the test method for thermal conductivity of a printed circuit board (hereafter referred to as
PCB) for high-brightness LEDs, the following factors are considered.
• The test method is applied to evaluate the relativity of both heat transfer and thermal
conductivity of PCBs consist of heterogeneous materials as shown in Figure A.2 in Annex
A which describes the heat transfer coefficient parameter as X-axis and thermal
conductivity parameter as Y-axis.
• The IEC 61189-3-913 employs a TEG chip as the heat source to replicate the heat
generated by LED chips.
• Heat dissipation characteristics of PCBs depend not only on the thermal conductivity of
the material properties, but also on the structure.
• In addition, convection and radiation from the specimen surface should be considered as
factors to affect the testing results.
• Considering the anisotropic nature of the heat dissipation of PCBs, different test methods
are employed for the plane (horizontal) and across the thickness (vertical) direction. The
combination of these tests should replicate a realistic environment.
• A TEG chip is employed with following considerations:
– measuring a small heat source such as an LED with thermocouples;
– ac
...