Guidelines for principal component reliability testing for LED light sources and LED luminaires

IEC TS 62861:2017(E) This Technical Specification provides guidelines for establishing confidence in product reliability using principal component testing for LED light sources and LED luminaires for general lighting. It includes methods and criteria using initial qualification tests and accelerated stress tests of the principal components. The performance of any principal component will influence the performance of the final product.
Techniques to validate full lifetime claims and lumen maintenance projection are outside the scope of this Technical Specification. The following principal components are included in the testing if they are used as an integral part for the LED light source or LED luminaire:
- LED package and interconnects;
- optical materials;
- electronic subassemblies;
- cooling systems, both active (e.g. fans) and passive (e.g. thermal interface material);
- construction materials.
This Technical Specification is not recommended for use as a normative reference to the LED product performance standards.

General Information

Status
Published
Publication Date
02-Mar-2017
Current Stage
PPUB - Publication issued
Start Date
03-Mar-2017
Completion Date
03-Mar-2017
Ref Project

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IEC TS 62861
Edition 1.0 2017-03
TECHNICAL
SPECIFICATION
Guidelines for principal component reliability testing for LED light sources and
LED luminaires
IEC TS 62861:2017-03(en)
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IEC TS 62861
Edition 1.0 2017-03
TECHNICAL
SPECIFICATION
Guidelines for principal component reliability testing for LED light sources and
LED luminaires
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.140.99 ISBN 978-2-8322-4017-5

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TS 62861:2017 © IEC 2017
CONTENTS

FOREWORD ........................................................................................................................... 6

INTRODUCTION ..................................................................................................................... 8

1 Scope .............................................................................................................................. 9

2 Normative references ...................................................................................................... 9

3 Terms and definitions .................................................................................................... 10

4 Component test conditions ............................................................................................ 13

5 LED package and interconnects .................................................................................... 14

5.1 General ................................................................................................................. 14

5.2 Sampling requirements ......................................................................................... 14

5.3 Production requirements ....................................................................................... 14

5.4 Assembly of LED packages on test boards............................................................ 15

5.5 Moisture preconditioning ....................................................................................... 15

5.6 Thermal characteristics ......................................................................................... 15

5.7 Pre- and post-stress electrical and photometric requirements ............................... 15

5.8 Pre- and post-stress visual inspection ................................................................... 15

5.9 Solderability and resistance to soldering heat ....................................................... 15

5.9.1 Solderability................................................................................................... 15

5.9.2 Resistance to soldering heat (RSH-reflow) test .............................................. 15

5.10 Failure criteria ....................................................................................................... 16

5.11 Initial qualification tests for LED packages ............................................................ 16

5.11.1 General ......................................................................................................... 16

5.11.2 Temperature and operation stress ................................................................. 17

5.11.3 Thermo-mechanical stress ............................................................................. 18

5.11.4 Temperature and humidity stress ................................................................... 18

5.11.5 Electrical stress – ESD-HBM ......................................................................... 19

5.11.6 Environmental stress ..................................................................................... 19

5.12 Initial qualification test for LED package interconnects – VVF ............................... 20

5.13 Accelerated stress tests for LED package interconnects ....................................... 20

5.13.1 General ......................................................................................................... 20

5.13.2 Interconnect temperature cycling (TMCL) ...................................................... 21

6 Optical materials............................................................................................................ 21

6.1 General ................................................................................................................. 21

6.2 Optical material test samples ................................................................................ 22

6.3 Moisture preconditioning ....................................................................................... 22

6.4 Pre- and post-stress photometric measurements ................................................... 22

6.5 Adhesion test ........................................................................................................ 23

6.6 Pre- and post-stress visual inspection ................................................................... 23

6.7 Failure criteria ....................................................................................................... 23

6.8 Initial qualification tests ........................................................................................ 23

6.8.1 Relative humidity (RH) ................................................................................... 23

6.8.2 Boiling water (BW) ......................................................................................... 24

6.8.3 Oven water (OW) ........................................................................................... 24

6.8.4 High temperature exposure (HTE) ................................................................. 24

6.9 Accelerated stress tests ........................................................................................ 24

6.9.1 Prediction models .......................................................................................... 24

6.9.2 Temperature and humidity (TH) ..................................................................... 25

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IEC TS 62861:2017 © IEC 2017 – 3 –

6.9.3 Temperature and light exposure (TL) ............................................................. 25

6.10 Light-transmitting materials ................................................................................... 26

6.11 Light-reflecting materials ....................................................................................... 26

6.11.1 Dichroic-coated glass and aluminium-coated glass ........................................ 26

6.11.2 Aluminium-coated plastic ............................................................................... 26

6.11.3 White plastic/non-coated plastic .................................................................... 26

6.12 Optical converters ................................................................................................. 27

7 Electronic subassemblies .............................................................................................. 27

7.1 General ................................................................................................................. 27

7.2 Sampling requirements ......................................................................................... 27

7.3 Production requirements ....................................................................................... 27

7.4 Pre- and post-stress electrical requirements ......................................................... 28

7.5 Pre- and post-stress visual inspection ................................................................... 28

7.6 Failure criteria ....................................................................................................... 28

7.7 Initial qualification tests ........................................................................................ 28

7.7.1 Temperature and operation stress (PTC) ....................................................... 28

7.7.2 Humidity and operation stress (HOT) ............................................................. 29

7.8 Accelerated stress tests ........................................................................................ 29

7.8.1 Prediction models .......................................................................................... 29

7.8.2 Temperature, humidity and operation stress (sequential ALT) ........................ 29

8 Active and passive cooling systems ............................................................................... 30

8.1 General ................................................................................................................. 30

8.2 Cooling system test samples ................................................................................. 31

8.3 Moisture preconditioning ....................................................................................... 32

8.4 Thermal resistance test ......................................................................................... 32

8.5 Performance parameter test .................................................................................. 32

8.6 Pre- and post-stress cooling performance requirements ........................................ 32

8.7 Pre- and post-stress visual inspection ................................................................... 32

8.8 Failure criteria ....................................................................................................... 32

8.9 Initial qualification tests ........................................................................................ 33

8.9.1 General ......................................................................................................... 33

8.9.2 Dust............................................................................................................... 33

8.10 Accelerated stress tests ........................................................................................ 34

8.10.1 General ......................................................................................................... 34

8.10.2 Cyclic temperature test (CT) with humidity and with/without operational

stress ............................................................................................................ 34

8.10.3 Temperature life test (TLT) passive cooling system ....................................... 34

8.10.4 Temperature life test (TLT) active cooling system .......................................... 35

9 Construction materials ................................................................................................... 35

9.1 General ................................................................................................................. 35

9.2 Mechanical components and interconnects ........................................................... 36

9.3 Mechanical interfaces between different components ............................................ 36

9.4 Chemical interactions ............................................................................................ 37

10 Final product testing ...................................................................................................... 38

10.1 General ................................................................................................................. 38

10.2 Principal component reliability in the final product ................................................. 38

10.3 Minimum validated AST time ................................................................................. 39

10.4 Final product qualification for reliability ................................................................. 40

11 Product updates ............................................................................................................ 40

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– 4 – IEC TS 62861:2017 © IEC 2017

Annex A (informative) Application profiles ............................................................................ 42

Annex B (informative) Acceleration models .......................................................................... 43

B.1 General ................................................................................................................. 43

B.2 Arrhenius model .................................................................................................... 43

B.3 Eyring model ......................................................................................................... 44

B.4 Coffin-Manson model ............................................................................................ 44

B.5 Norris-Landzberg model ........................................................................................ 44

B.6 (Inverse) power law............................................................................................... 45

B.7 Peck model ........................................................................................................... 45

B.8 Generalized Eyring model ..................................................................................... 45

B.9 Sample size calculation ........................................................................................ 46

B.10 Basic guidelines .................................................................................................... 47

B.11 Example................................................................................................................ 47

Annex C (informative) System reliability ............................................................................... 49

C.1 General ................................................................................................................. 49

C.2 Basic principles ..................................................................................................... 49

C.3 Testing on the system level ................................................................................... 49

C.4 System reliability prediction .................................................................................. 50

C.4.1 General ......................................................................................................... 50

C.4.2 Block diagrams .............................................................................................. 50

C.4.3 Fault tree ....................................................................................................... 51

C.4.4 Markov chains ............................................................................................... 51

C.4.5 Bayesian networks ......................................................................................... 51

C.4.6 Chi-square ..................................................................................................... 52

Annex D (informative) Qualification flowcharts ..................................................................... 54

D.1 General ................................................................................................................. 54

D.2 Qualification flowcharts of principal components ................................................... 54

Annex E (informative) Physical analysis for principal components ........................................ 59

E.1 General ................................................................................................................. 59

E.2 DPA for LED packages and interconnects ............................................................. 59

E.3 DPA for optical materials ...................................................................................... 60

E.4 PA for electronics ................................................................................................. 60

E.5 PA for active and passive cooling systems ............................................................ 61

E.6 DPA for mechanical .............................................................................................. 61

Annex F (normative) Principal component test report ........................................................... 62

Bibliography .......................................................................................................................... 64

Figure D.1 – Qualification flowchart for LED package and interconnects ............................... 54

Figure D.2 – Qualification flowchart for optical materials ....................................................... 55

Figure D.3 – Qualification flowchart for electronic subassemblies ......................................... 56

Figure D.4 – Qualification flowchart for active and passive cooling systems .......................... 57

Figure D.5 – Qualification flowchart for construction materials .............................................. 58

Table 1 – Mapping the LED package interconnects qualification tests to the useable

acceleration model with typical range of the acceleration factor ............................................ 20

Table 2 – Duration (cycles) of temperature application .......................................................... 21

Table 3 – Mapping of the optical-material related accelerated stress tests ............................ 24

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IEC TS 62861:2017 © IEC 2017 – 5 –
Table 4 – Mapping the electronic subassembly qualification tests to the useable

acceleration model with typical range of the acceleration factor ............................................ 29

Table 5 – Example ALT profile for an electronic subassembly ............................................... 30

Table 6 – Examples of stressors, affected part of the cooling systems and its reliability

effect. ................................................................................................................................... 31

Table 7 – Mapping the cooling system qualification tests to the useable acceleration

model with typical range of the acceleration factor ................................................................ 34

Table 8 – List of undesired chemicals in LED products for general lighting. .......................... 38

Table 9 – Influence of the principal components on the final product. .................................... 39

Table 10 – Example list of validated AST times. .................................................................... 40

Table 11 – Minor and major change list per principal component. ......................................... 41

Table A.1 – Example of two application profiles .................................................................... 42

Table B.1 – Sample sizes versus confidence and reliability level assuming L = T × AF .......... 47

Table B.2 – Example of calculated acceleration factors ......................................................... 48

Table C.1 – Example test scheme and results for Chi-square................................................ 53

Table F.1 – Example overview reporting format .................................................................... 63

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– 6 – IEC TS 62861:2017 © IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
GUIDELINES FOR PRINCIPAL COMPONENT RELIABILITY
TESTING FOR LED LIGHT SOURCES AND LED LUMINAIRES
FOREWORD

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all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

The main task of IEC technical committees is to prepare International Standards. In

exceptional circumstances, a technical committee may propose the publication of a technical

specification when

• the required support cannot be obtained for the publication of an International Standard,

despite repeated efforts, or

• the subject is still under technical development or where, for any other reason, there is the

future but no immediate possibility of an agreement on an International Standard.

Technical specifications are subject to review within three years of publication to decide

whether they can be transformed into International Standards.

IEC TS 62861, which is a Technical Specification, has been prepared by subcommittee 34A:

Lamps, of IEC technical committee 34: Lamps and related equipment.
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IEC TS 62861:2017 © IEC 2017 – 7 –
The text of this Technical Specification is based on the following documents:
Enquiry draft Report on voting
34A/1884/DTS 34A/1966/RVDTS

Full information on the voting for the approval of this technical specification 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.

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
• transformed into an International standard,
• 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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– 8 – IEC TS 62861:2017 © IEC 2017
INTRODUCTION

LED products depend generally on how balanced its principal components are in terms of

their reliability. It is not only the LED components that determine product performance, but

also other parts of the LED product play an equally important role. For instance, electronic

subassemblies, optics, mechanics and the involved cooling method play such a role.

This Technical Specification envisions a methodology, which addresses separate

subcomponent reliability data, to provide a basis for statistical system reliability design.

Standardized reporting formats and flowcharts are presented.

Next, protocols based on accelerated methods are given to estimate system reliability of the

final product using subcomponent data.

Verification of LED product lifetime is based on a ‘test to pass’ principle, which means the

components of the product under test are evaluated to give equivalent reliability confidence to

that which would be achieved by real-time life testing of the complete LED product. The tests

described in this Technical Specification are divided into: initial qualification tests (IQT) giving

confidence of basic component robustness, but not linked to any specific lifetime projection,

and accelerated stress tests (AST) giving confidence of reliability to a specific lifetime (within

the specified constraints of the test).

Since the approach foreseen in this Technical Specification covers a generic methodology, it

can be seen as guidance related to relevant product performance standards, such as the LED

lamp performance standard IEC 62612, the LED module performance standard IEC 62717

and LED luminaire performance standard IEC 62722-2-1. This Technical Specification is not

recommended for use as a normative reference to the LED product performance standards.

This Technical Specification addresses the need for a document giving guidance that is

developed according to consensus procedures and in itself is normative in nature, while at the

same time recognizing that LED technology for lighting products is still in an emerging phase.

This Technical Specification approaches an International standard in terms of detail and

completeness.
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IEC TS 62861:2017 © IEC 2017 – 9 –
GUID
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