Table Of Contenti
Délivré par l’Université Toulouse 3–Paul Sabatier
Présentée et soutenue par
Sovannarith LENG
le 20 Février 2017
Identifying and Evaluating Aging Signatures
in Light Emitting Diode Lighting Systems
École doctorale et discipline ou spécialité
ED GEET : Génie Electrique
Unité de recherche
Laboratoire PLAsma et Conversion d’Energie (LAPLACE)
Directeurs de Thèse
Dr. Laurent CANALE, CNRS, LAPLACE
Prof. Georges ZISSIS, Université Paul Sabatier, LAPLACE
Jury
Christian GLAIZE, Professeur, Lab. IES, Groupe GEM, Montpellier, Rapporteur
Yannick DESHAYES, Dr/HDR, IMS, Groupe ONDE, EDMINA, Talence, Rapporteur
Geneviève DUCHAMP, Professeur, IMS, Groupe FIABILITE, Bordeaux, Examinateur
Laurent MASSOL, Ingénieur, Directeur Société LED, Montauban, Invité
Laurent CANALE, Dr, Ingénieur de Recherche CNRS, LAPLACE, Directeur de Thèse
Georges ZISSIS, Professeur, Univ. Paul Sabatier, LAPLACE, Directeur de Thèse
ii S.LENG, Identif. & Eval. Aging Signatures in LED Lighting Systems
Université Toulouse 3–Paul Sabatier
Laboratoire LAPLACE
THÈSE
Pour obtenir le grade de
DOCTEUR DE L’UNIVERSITÉ
Spécialité
Identifying and Evaluating Aging
Signatures in Light Emitting Diode
Lighting Systems
Sovannarith LENG
Présentée et soutenue publiquement
Le 20 Février 2017
Directeurs
Dr. Laurent CANALE, Ingénieur de Recherche CNRS, LAPLACE
Prof. Georges ZISSIS, Université Paul Sabatier, LAPLACE
JURY
Christian GLAIZE, Professeur, Lab. IES, Groupe GEM, Montpellier, Rapporteur
Yannick DESHAYES, Dr/HDR, IMS, Groupe ONDE, EDMINA, Talence, Rapporteur
Geneviève DUCHAMP, Professeur, IMS, Groupe FIABILITE, Bordeaux, Examinateur
Laurent MASSOL, Ingénieur, Directeur Société LED, Montauban, Invité
Laurent CANALE, Dr, Ingénieur de Recherche CNRS, LAPLACE, Directeur de Thèse
Georges ZISSIS, Professeur, Univ. Paul Sabatier, LAPLACE, Directeur de Thèse
iv S.LENG, Identif. & Eval. Aging Signatures in LED Lighting Systems
v
ACKNOWLEDGEMENTS
This thesis was carried out within the PLAsma and Conversion d'Energie
(LAPLACE) laboratory in Toulouse. This exciting and rewarding research has
led to the contribution of several staff from the laboratory. I would therefore like
to express my gratitude to certain individuals who have devoted their efforts and
their availabilities to me during this thesis.
First of all, I would like to express my deep gratitude to my supervisor,
Georges ZISSIS, Professor at University Paul Sabatier in Toulouse, Head of
Light & Matter Research Group at LAPLACE and Director of SH2D Research
Federation, for his very important direction in my work and for his
encouragement, his advice and his very valuable technical and moral support for
the success of my work.
I would also like to express my sincere thanks to my co–supervisor,
Dr. Laurent CANALE, CNRS Research Engineer in Light & Matter Research
Group and AFE Midi–Pyrénées Region Chairman, for his encouragement, his
guidance, including his very useful advice which enabled me to acquire
knowledge and skills that are very useful for my research and my career.
I especially wish to thank my thesis committee: Professor Christian
GLAIZE, at "Institut d'Electronique et des Systèmes" in Montpellier, Professor
Geneviève DUCHAMP, and Dr Yannick DESHAYES, Associate Professor/HDR,
both from University of Bordeaux and "Laboratoire de l'Intégration du Matériau
au Système", for their valuable advices, thesis supervision, and their positive
comment and evaluation on my thesis.
I do not forget to express my gratitude to all staffs, lecturers, professors,
PhD students and colleagues of the Laplace with whom I shared very pleasant
moments and which allowed me to acquire various technical, social and cultural
vi S.LENG, Identif. & Eval. Aging Signatures in LED Lighting Systems
knowledges on countless occasions. I would like to specially thank to my best
friends, Alaa ALCHADDOUD and Feng TIAN.
I also do not forget to convey my thanks to my Cambodian friends who are
/ were in Toulouse and France, with whom I shared a lot of pleasant moments
and who remain anchored in my memories.
Very special and from bottom of heart thanks and gratitude to my beloved
family: my wife, my son and my parent for their love, constant moral
encouragement, and their invaluable sacrifice of everything for me. They always
support and hold me when I am down so I never lost my spirit. No word I can say
about their goodness. I am very proud to be their part of family. I also thank to
my brothers and sisters for caring and support. It is to all of them that I dedicate
this thesis.
The last but not least, I would like to express my deepest appreciation to
Erasmus Mundus Techno II project with the support of the Erasmus Mundus
Program of the European Union for my financial support, to officers and staffs of
the Techno II program for their kindness and help during my study.
vii
Contents
INTRODUCTION ...................................................................................................... 1
1. STATE OF THE ART OF THE GaN LEDS TECHNOLOGY .............................. 5
1.1. HISTORY OF LIGHTING SYSTEMS ............................................................................ 6
1.1.1. The Sun ......................................................................................... 6
1.1.2. Incandescent Filament Lamp ............................................................. 7
1.1.3. Mercury and Sodium Vapor Lamps ..................................................... 7
1.1.4. Fluorescent Lamp ............................................................................ 9
1.1.5. Light–Emitting Diodes (LEDs) .......................................................... 10
1.2. LED CHIP STRUCTURES ....................................................................................... 14
1.2.1. Conventional Lateral and Vertical Structure ....................................... 14
1.2.2. Flip Chip Structure ......................................................................... 15
1.2.3. Vertical Thin Film Structure ............................................................. 16
1.2.4. Thin Film Flip Chip Structure ........................................................... 17
1.3. PACKAGING OF LEDS .......................................................................................... 18
1.3.1. Low Power LED Package ................................................................. 19
1.3.2. High Power LED Package ................................................................ 19
1.3.3. Packaging Process ......................................................................... 21
1.3.3.1. Dual in–Line (DIP) Packaging ................................................................... 22
1.3.3.2. SMD LED Packaging .................................................................................. 22
1.3.3.2.1. SMD Leadform Packaging ....................................................................... 23
1.3.3.2.2. SMD Leadless Package ............................................................................ 24
1.3.3.3. LED Array Packaging ................................................................................. 26
1.4. MAIN DEGRADATION OF LEDS TECHNOLOGY....................................................... 29
1.4.1. Degradation and Failure Modes at Chip Level ..................................... 29
1.4.1.1. Generation and Movement of Defect and Dislocation ............................... 29
1.4.1.2. Die Cracking ................................................................................................ 32
1.4.1.3. Dopant Diffusion ......................................................................................... 34
1.4.1.4. Electromigration ......................................................................................... 34
1.4.2. Interconnection Failure Modes ......................................................... 35
1.4.2.1. Bond Wire /Wire Ball Bond Failure ........................................................... 35
1.4.2.2. Electrical Contact Metallurgical Interdiffusion......................................... 37
1.4.2.3. Electrostatic Discharge ............................................................................... 37
1.4.3. Degradation and Failure Modes at Package Level ................................ 40
1.4.3.1. Carbonization of the Encapsulant .............................................................. 40
1.4.3.2. Delamination ............................................................................................... 41
1.4.3.3. Lens /Encapsulant Failure ......................................................................... 43
1.4.3.4. Phosphor Thermal Quenching .................................................................... 44
viii S.LENG, Identif. & Eval. Aging Signatures in LED Lighting Systems
1.4.3.5. Solder Joint Fatigue ................................................................................... 46
1.5. CONCLUSION – CHAPTER 1 ................................................................................. 47
2. ELECTRICAL AND OPTICAL CHARACTERISTICS OF LEDS ..................... 51
2.1. METHODOLOGY FOR JUNCTION TEMPERATURE EVALUATION ............................... 52
2.1.1. Temperature Dependence of Forward Voltage (Vf) .............................. 53
2.2. OPTICAL PROPERTIES OF LED ................................................................... 60
2.2.1. Internal, Extraction, External, and Power Efficiencies .......................... 60
2.2.2. Emission Spectrum ........................................................................ 61
2.2.3. Light Escape Cone ......................................................................... 64
2.2.4. Radiation Pattern–Lambertian Emission Pattern .................................. 66
2.2.5. Epoxy Encapsulant ........................................................................ 67
2.2.6. Temperature Dependence of Emission Intensity ................................. 68
3. EXPERIMENTAL SETUP FOR LED AGING EVALUATION ......................... 69
3.1. A NEW PROTOTYPE OF LED AGING BENCH ............................................. 70
3.2. TEMPERATURE CONTROLLER (REX–D100) ........................................................ 76
3.2.1. Software Program for REX–D100 Temperature Controller ..................... 78
3.2.2. Communication Protocol ................................................................. 80
3.2.2.1. Polling Procedure ........................................................................................ 80
3.2.2.1. Selection Procedure .................................................................................... 81
3.3. SOURCE–METER UNIT (SMU–KEITHLEY 2602A) ............................................... 81
3.3.1. 2–Wires and 4–Wires Feature .......................................................... 82
3.3.2. Software Program Measurement for SMU–Keithley 2602A .................... 83
3.4. IMPEDANCE ANALYZER (SOLARTRON MODULAB) ................................................ 87
3.4.1. Instrument Group Modules ............................................................. 87
3.4.2. PC Communication Setup ............................................................... 88
3.4.3. Software Program Control of Solartron ModuLab ................................ 89
3.5. SPECTROMETER (SPECBOS 1201) ........................................................................ 91
3.5.1. Optical Measurement Hardware Setup .............................................. 92
3.5.2. Software Program Measurement of Specbos 1201 .............................. 93
3.6. LED’S DRIVER .................................................................................................... 94
4. EVALUATION OF FAILURE MECHANISMS FOR LEDS STUDIED ............ 97
4.1. EFFECT OF TEMPERATURE ON LED PERFORMANCE............................................ 98
4.2. SELF−HEATING TEST........................................................................................ 100
4.3. INITIAL STATE OF ELECTRICAL CHARACTERIZATIONS....................................... 101
4.4. ELECTRICAL FAILURE SIGNATURES ................................................................... 110
ix
4.4.1. Electrical Aging Characteristic of Cree’s Devices................................ 111
4.4.2. Electrical Aging Characteristic of Osram’s Devices ............................. 115
4.4.3. Electrical Aging Characteristic of Philips’s Devices ............................. 118
4.4.4. Electrical Aging Characteristic of Seoul’s Devices .............................. 122
4.5. OPTICAL FAILURE SIGNATURES ......................................................................... 126
4.5.1. Initial State of Photometric Characterization .................................... 127
4.5.2. Photometrical Characterizations of LEDs under accelerated
aging conditions ................................................................................... 136
4.6. CONCLUSION– CHAPTER 4 ................................................................................ 146
GENERAL CONCLUSION AND PERSPECTIVES ............................................. 149
REFERENCES............................................................................................................ 155
ANNEXES ...................................................................................................................I
APPENDIX A: COMMUNICATION IDENTIFIER LIST OF REX–D100 ................................. II
APPENDIX B: CONTROLLER SCANNED PARAMETER ...................................................... IV
APPENDIX C: PROGRAM CODE FOR REX–D100 ............................................................ V
APPENDIX D: PROGRAM CODE FOR SMU KEITHLEY 2602A ........................................ XI
APPENDIX F: DATASHEET OF LEDS ........................................................................ XXXI
x S.LENG, Identif. & Eval. Aging Signatures in LED Lighting Systems
......................................................................................................................................
Liste des tableaux
Table I.1: Discoveries and History of LEDs ......................................................... 13
Table I.2: Comparison of Key Characteristics and Parameter Values for
Commercial ............................................................................................................. 14
Table I.3: Factors influent LED packaging .......................................................... 21
Table II.1: Varshni parameters of common semiconductors. ............................... 57
Table III.1: Main characteristics of studied LEDs. ............................................... 71
Table IV.1: dispersion of I−V characteristic of 16 Samples each LED group
computed at V=2.9V. ............................................................................................ 104
Table IV.2: Error of variation of luminance and spectrum of 16 samples each
unstressed LED group @350mA. ......................................................................... 131
Table des illustrations
Figure I.1: Sun, the first light source. ..................................................................... 6
Figure I.2: Artificial Lighting. ................................................................................. 6
Figure I.3: Mercury Vapor Lamp. ............................................................................ 7
Figure I.4: Low–pressure sodium vapor lamp......................................................... 8
Figure I.5: High–pressure sodium vapor lamp. ...................................................... 9
Figure I.6: Fluorescent lamp. ................................................................................. 10
Figure I.7: Publication of JH Round in Electrical World. ..................................... 11
Figure I.8: A replication of H. J. Round's LED experiments. ............................... 11
Figure I.9: a) Lateral structure, b) vertical structure. .......................................... 15
Figure I.10: Flip chip structure. ............................................................................ 16
Figure I.11: LED ThinGaN structure by Osram. .................................................. 16
Figure I.12: TFFC by Philips Lumiled. ................................................................. 17
Figure I.13: SEM images of PSS and GaN grown on PSS . .................................. 17
Figure I.14: SEM of an N–face GaN surface roughening etched by a KOH–based
PEC method . .......................................................................................................... 18
Figure I.15: Al–oxide honeycomb nanostructure on thin–GaN LED . ................. 18
Figure I.16: a) LED with hemispherical encapsulant, b) LEDs with cylindrical
and rectangular encapsulant . ............................................................................... 19
