Solid State Lighting Reliability Part 2 (eBook)

Willem Dirk van Driel is the Solid State Lightning Reliability Program Manager for Philips Lighting Eindhoven, and is Assistant Professor of Micro/Nano Reliability at Delft University of Technology, in the Electronic Components, Technology and Materials Department. Xuejun Fan is Professor in the Department of Mechanical Engineering at Lamar University. G.Q. Zhang is Professor of Micro/Nanoelectronics, System Integration and Reliability (MSI&R) at  the Delft University of Technology.

Preface 5
Personal Acknowledgments 7
Contents 8
Chapter 1: Quality and Reliability in Solid-State Lighting: Qua Vadis? 11
1.1 What We Predicted: A New Era in Lighting 11
1.2 What Is the Current Status? 15
1.3 What´s Next: SSL Reliability, Qua Vadis? 18
1.4 Final Remarks 22
References 22
Chapter 2: Chip-Level Degradation of InGaN-Based Optoelectronic Devices 24
2.1 Defect Generation 24
2.1.1 Increase in Non-radiative Losses 25
2.1.2 Increase in Shunt Current 26
2.2 Diffusion Processes 27
2.3 Degradation of the Ohmic Contacts 32
2.4 Electromigration 34
2.5 Cracking Due to Mismatch 36
2.6 Electrostatic Discharge (ESD) 38
2.6.1 Role of Defects and Internal Capacitance 39
2.6.2 ESD Effects 41
2.6.3 Structure Improvements 43
2.7 Electrical Overstress (EOS) 46
2.8 Reverse-Bias Degradation 47
2.9 Conclusions 49
References 51
Chapter 3: LED Early Failures: Detection, Signature, and Related Mechanisms 58
3.1 Introduction 58
3.2 Early Failures in Reliability Studies 60
3.3 Early Failures from an LED Manufacturing Variability Point of View 62
3.3.1 Batch-to-Batch Variability 62
3.3.1.1 Batch, Lot, Wafer, and Die Definitions 62
3.3.1.2 Lot-to-Lot, Wafer-to-Wafer, and Within-Wafer Variabilities 63
3.3.1.3 Tool-to-Tool Variability 63
3.3.2 Soft Fails 65
3.3.2.1 Wafer Substrate 65
3.3.2.2 Chemical Mechanical Polishing (CMP) 65
3.3.2.3 Lithography Misalignment 66
3.3.2.4 Chemicals Used in Lithography Developers, CMP or Etchants 66
3.3.2.5 Standard Metrology Limitations 67
3.3.2.6 Crystal Growth 67
3.3.3 Hard Fails 68
3.3.3.1 Process Improvement: Release to Manufacturing 68
3.3.3.2 Process Recipe Error 69
3.3.4 Early Failure from an LED Assembly Side: Detection Methods 70
3.3.5 Electrical Characterizations and Model 71
3.3.6 Experiment 73
3.4 Early Failure: Signature and Related Defects 75
3.4.1 Electrical Signatures 75
3.4.2 Identification of Early Failure-Related Defects 76
3.4.3 Relation Between Initial Defects and Lower Lifetime 80
3.5 Conclusion 81
References 83
Chapter 4: Advances in Reliability Testing and Standards Development for LED Packages and Systems 85
4.1 State of the Art of the Reliability Test Standards 86
4.2 Advanced Lumen Maintenance Lifetime Estimation Methods 91
4.3 A Temperature-Driven Accelerated Test Method 94
4.3.1 Boundary Curve Definition 94
4.3.2 Two-Stage Process 96
4.3.3 Parameters Determination 97
4.3.4 Determination of the Accelerated Time 98
4.3.5 Verification 100
4.4 A SPD-Based Degradation Prediction Method 105
4.4.1 Spectral Power Distribution Models 107
4.4.2 Degradation Prediction 113
4.5 Conclusions 117
References 119
Chapter 5: Reliability and Lifetime Assessment of Optical Materials in LED-Based Products 123
5.1 LED and the LED Landscape 124
5.2 White Light LEDs 127
5.3 Failure Mechanisms in LEDs 127
5.4 Aging of Optical Materials and Origins of Color Shift 128
5.4.1 Contaminations 129
5.4.2 Interface Delamination 129
5.4.3 Discoloration 130
5.5 Yellowing of Encapsulant/Lens 132
5.6 Terms and Definitions of Color Shifting 135
5.7 Reliability Performance of LEDs 139
5.8 Highly Accelerated Stress Test (HAST) Setup 140
5.9 Reliability Models 141
5.9.1 Effect of Light Intensity on the Acceleration of Aging Test 143
5.9.2 Effect of Light Intensity on the Time to Failure of Remote Phosphor 144
5.10 Concluding Remarks 144
References 145
Chapter 6: The Influence of Phosphor and Binder Chemistry on the Aging Characteristics of Remote Phosphor Products 148
6.1 Introduction 148
6.2 Methods 149
6.2.1 Wet High-Temperature Operational Lifetime (WHTOL) Test 150
6.2.2 Testing the RPD Samples 151
6.3 Results 151
6.3.1 Cool White Remote Phosphor Samples 152
6.3.2 Warm White Remote Phosphor Samples 155
6.3.3 FTIR Studies of Binder Properties 158
6.4 Discussion 160
6.5 Conclusions 162
References 163
Chapter 7: Thermal Characterization of Die-Attach Material Interface of High-Power Light-Emitting Diodes 165
7.1 Introduction 165
7.2 Transient Behavior of LED Junction Temperature 166
7.2.1 Transient Voltage Behavior of LED 167
7.2.2 Measurement of Transient LED Junction Temperature 167
7.3 Transient Domain for Inverse Approach 171
7.3.1 Hybrid Analytical/Numerical Model 172
7.3.2 DTI Dominant Domain 175
7.4 Inverse Approach to Determine the Resistance of DTI 177
7.5 Validity of DTI Resistance 179
7.6 Conclusion 180
References 182
Chapter 8: Color Quality 185
8.1 Introduction 185
8.2 Chromaticity 186
8.2.1 Chromaticity Coordinates and Chromaticity Diagrams 186
8.2.2 Chromaticity Specifications for Lighting Products 189
8.2.3 Correlated Color Temperature 190
8.2.4 Duv 191
8.2.5 Perception of White Light Chromaticity 192
8.2.6 Color Difference of Light Source 194
8.3 Object Color Specifications 195
8.4 Color Rendering Characteristics 197
8.4.1 Color Rendering Index 197
8.4.2 Color Preference and Perception 199
8.5 Luminous Efficacy 201
8.6 Color Characteristics of Single Color LEDs 202
8.6.1 Dominant Wavelengthlambdad 202
8.6.2 Centroid Wavelengthlambdac 204
8.6.3 Peak Wavelengthlambdap 204
References 204
Chapter 9: LED-Based Luminaire Color Shift Acceleration and Prediction 206
9.1 Introduction 207
9.2 Breakdown Method for Color Shift and Mechanism Investigation 207
9.2.1 Materials and Methods 207
9.2.2 Results and Discussions 210
9.2.2.1 PMMA 210
9.2.2.2 Microcellular PET 212
9.2.2.3 LED Package 215
9.3 A Novel Approach for Color Shift Investigation on LED-Based Luminaires 215
9.3.1 Materials and Methods 215
9.3.2 Results and Discussions 218
9.3.2.1 Measured Results for Color Shift of Downlights After Aging 218
9.3.2.2 Inputs for Simulation 219
9.3.2.3 Color Shift Results 220
9.3.2.4 Comparison and Discussion 221
9.4 Luminaire Color Shift Acceleration and Prediction 222
9.5 Conclusions 223
References 223
Chapter 10: Chromaticity Maintenance in LED Devices 225
10.1 Introduction 225
10.2 Representing Chromaticity Shifts 227
10.3 LED-Induced Chromaticity Shifts 229
10.3.1 Experimental Studies 230
10.3.2 LED Chromaticity Shift Mechanisms 233
10.3.3 Causes of Chromaticity Shifts in LEDs 236
10.3.3.1 LED Structures 236
10.3.3.2 LED Package Substrates 237
10.3.3.3 Phosphors 237
10.3.3.4 Encapsulants 239
10.3.3.5 Contaminants 239
10.4 Projecting Chromaticity Shifts in LEDs 240
10.5 Optical Materials and Chromaticity Shifts 240
10.5.1 Lens Aging 242
10.5.2 Modeling the Degradation of Lens Materials 244
10.5.3 Modeling the Degradation of Reflectors 247
10.5.4 Modeling the Degradation of Lens Materials 249
10.6 Luminaire Design Effects 251
10.7 Conclusions 254
References 255
Chapter 11: Fault Diagnostics and Lifetime Prognostics for Phosphor-Converted White LED Packages 259
11.1 Introduction 260
11.2 Prognostics and Health Management 264
11.2.1 PoF-Based PHM 264
11.2.2 Data-Driven-Based PHM 268
11.3 In Situ Monitoring and Anomaly Detection for Phosphor-Converted White LED Packages 275
11.3.1 Test Vehicle, Experimental Setup, and Data Collection 276
11.3.2 Theory and Methodology 276
11.3.3 Implementation Results and Discussion 281
11.4 Prognostic of Lumen Maintenance Lifetime for Phosphor-Converted White LED Packages 282
11.4.1 Methodologies and Algorithms 285
11.4.2 Implementation Results and Discussion 290
11.5 Conclusions 296
References 298
Chapter 12: Advances in LED Solder Joint Reliability Testing and Prediction 304
12.1 Introduction 304
12.1.1 Solder Joints in Solid-State Lighting Package 304
12.1.2 Challenges for Solder Reliability Assessment in SSL System 305
12.1.3 Challenges for the Prognostic of Remaining Useful Life of Solder Joint in SSL System 308
12.2 Fatigue Model Derivation for Solder Joint in LGA Assembly 309
12.2.1 Constitutive Law and Material Models 310
12.2.2 Finite Element Modeling 312
12.2.3 Model Derivation 316
12.3 Geometric Effects of Solder Joint on Board Level Solder Reliability in SSL System 321
12.3.1 Modeling and Simulation Details 322
12.3.2 Parametric Studies and Response Surface Analysis 323
12.4 In Situ High-Precision Fatigue Damage Monitoring During Accelerated Testing of Solder Joint 331
12.4.1 Geometric Details of Test Sample 333
12.4.2 Temperature Sensor Calibration 335
12.4.3 Thermomechanical Test 335
12.4.4 In Situ DC Electrical Resistance Monitor Setup 335
12.4.5 Micro-tomography Scans of the Solder Assembly 339
12.4.6 Temperature Coefficient of Resistivity of SAC 305 339
12.4.7 Finite Element Model and Simulation Details 341
12.4.8 Monitored Fatigue Damage Evolution and Crack Initiation Determination 343
12.5 Summary 349
References 350
Chapter 13: Online Testing Method and System for LED Reliability and Their Applications 355
13.1 Introduction 355
13.2 Online Testing System: Principle and Method 358
13.3 System Optimization 362
13.4 Experimental Verification and a Benchmark 364
13.5 Error Estimation 366
13.6 Application I: Effect of Packaging Materials on the Degradation Mechanism of LEDs 368
13.7 Application II: Effect of Silicone Amount on the Lumen Maintenance of LEDs 374
13.8 Summary 379
References 380
Chapter 14: Degradation Mechanisms of Mid-power White-Light LEDs 382
14.1 Introduction 383
14.2 Optical Degradation Mechanisms Under HTOL 385
14.2.1 Experiment Setup 385
14.2.2 Results and Discussion 388
14.2.2.1 Optical Degradation Characteristics 388
14.2.2.2 Spectrum Analysis 390
14.2.2.3 Chip Deterioration by I-V Characteristic Analysis 392
14.2.2.4 Package Degradation Investigation by Physics Analysis 394
14.3 Optical Degradation Mechanisms Under WHTOL Test 400
14.3.1 Experiment Setup 400
14.3.2 Results 401
14.3.2.1 Lumen Degradation 401
14.3.2.2 Color Shift 403
14.3.2.3 Electrical Characteristics 405
14.3.2.4 Failure Analysis 407
14.3.3 Discussion 410
14.3.3.1 Optical Degradation Mechanisms: Effects of Chip Deterioration 410
14.3.3.2 Optical Degradation Mechanisms: Effects of Package Material Degradation 412
14.4 Optical Degradation Mechanisms Under HAST 416
14.4.1 Motivation Example 416
14.4.2 High-Temperature Storage 416
14.4.3 Discussion of the Root Cause of Silicone Carbonization 418
14.4.3.1 Joule Heating Effects of the LED Packages 419
14.4.3.2 Self-Heating Effects of the Phosphors 421
14.4.3.3 Blue Light Over-Absorption by Silicone 425
14.4.3.4 Simulation and Validation 427
14.5 Summary 429
References 430
Chapter 15: Assessing the Reliability of Electrical Drivers Used in LED-Based Lighting Devices 434
15.1 Introduction 434
15.2 Basics of LED Device Drivers 435
15.2.1 Common Driver Topologies 435
15.2.2 Key Driver Components of LED Device Drivers 435
15.2.3 Common Driver Topologies 440
15.2.4 Common Electrical Stresses in LED Device Drivers 442
15.3 Accelerated Stress Tests for Electronics 443
15.4 Accelerated Testing of Components and Luminaires 446
15.5 Conclusions 453
References 453
Chapter 16: Reliability Prediction of Integrated LED Lamps with Electrolytic Capacitor-Less LED Drivers 456
16.1 Introduction 457
16.2 Coupling Effects of Degradations 459
16.2.1 Degradation Modelling 460
16.2.1.1 LED Light Source 460
16.2.1.2 LED Driver 461
16.2.2 Simulation Methodology 462
16.2.2.1 Electronic Simulations 462
16.2.2.2 Thermal Simulations 464
16.2.2.3 Simulation Methodology 465
16.2.3 Results and Discussions 466
16.2.3.1 Parameter Extraction of LED Models 466
16.2.3.2 Lamp´s Initial Temperature Distributions 467
16.2.3.3 Definition of Different Scenarios 467
16.2.3.4 Results and Discussions 468
LED Current 468
LED Junction Temperature 468
Driver´s Temperature 470
Lumen Maintenance and Lifetime 470
16.3 The Catastrophic Failure Under Lumen Depreciation 472
16.3.1 General Methodology 473
16.3.2 Modelling 473
16.3.2.1 Driver Circuit 473
16.3.2.2 Model of LED Light Source 475
16.3.2.3 Thermal Model 475
16.3.3 Fault Tree and Failure Rate Models 476
16.3.4 Case Studies and Results 477
16.3.4.1 Selection of LED and Driver 477
16.3.4.2 Results and Discussions 478
Constant Light Output (CLO) Mode 478
Constant Current Mode (CCM) 479
16.4 Conclusions 483
References 484
Chapter 17: Statistical Analysis of Lumen Depreciation for LED Packages 488
17.1 Introduction 488
17.2 Problem Formulation 490
17.3 Statistical Methods 490
17.3.1 Current Agreed Methods 490
17.3.2 Alternative for Model Fitting 494
17.4 Analysis of the Selected Use Cases 495
17.4.1 Mid-power and High-Power LED Technology 495
17.4.2 Deep Dive into High-Power LED Technology 497
17.5 Conclusions and Discussion 501
References 502
Chapter 18: Long-Term Reliability Prediction of LED Packages Using Numerical Simulation 504
18.1 Introduction 504
18.2 Fatigue Life Evaluation of Wire Bonds During a Thermal Shock Cycle Test 506
18.2.1 Wire Bonding Lifetime Model 507
18.2.1.1 Experiments 507
18.2.1.2 Finite Element Model 509
18.2.1.3 Calibrated Model 510
18.2.2 A LED Package Design Example Using the Wire Bond Lifetime Model 513
18.3 Quantification of Silicone Degradation During HTOL 514
18.3.1 Linear Viscoelastic Model of PDMS 516
18.3.2 Finite Element Analysis 519
18.3.3 Lumen Depreciation Model 519
18.3.4 A LED Package Design Example Using the Lumen Depreciation Model 523
18.4 Conclusions 523
References 525
Chapter 19: Corrosion Sensitivity of LED Packages 527
19.1 Introduction 528
19.2 Sources of Corrosion 528
19.2.1 Intrinsic Corrosion 529
19.2.2 Extrinsic Corrosion 531
19.2.2.1 Corrosion by Components of Light Source 531
19.2.2.2 Corrosion by Outgassing of Materials from the Environment 532
19.2.2.3 Corrosion by Air Pollution 532
19.3 Sensitivity to Corrosion by LED Package Design 533
19.3.1 Package Integrity 533
19.3.2 Corrosion-Sensitive Materials 535
19.3.3 Hitting Probability on Surface 536
19.4 Corrosion Test Methods 538
19.4.1 Standard Test Methods 538
19.4.2 Accelerated Test Methods 540
19.5 Test Results 541
19.5.1 Sulfur Testing 541
19.5.2 Testing with Halogen Gasses 543
19.5.3 Testing with VOCs 543
19.6 Harmful Chemicals 544
19.7 Conclusion 546
References 546
Chapter 20: Reliability Management of a Light-Emitting Diode for Automotive Applications 548
20.1 Introduction 548
20.2 Accelerated Life Testing 550
20.3 Automotive Qualification Process 551
20.3.1 Motivation 551
20.3.2 Automotive Qualification Standards AEC Q101/IEC 60810 552
20.3.3 Why Do We Need LED Qualification? 553
20.4 LED Qualification Testing According to IEC 60810 554
20.4.1 Sample Selection and Family Definition of LED Packages 554
20.4.2 Moisture Preconditioning and Assembly of LED Packages 556
20.4.3 Thermal Management 557
20.4.4 Sample Lot and Production Requirements 560
20.4.5 Qualification Stress Tests 560
20.4.5.1 Temperature and Bias Operation 562
20.4.5.2 Temperature, Humidity and Bias Operation 562
20.4.5.3 Thermo-mechanical Stress 564
20.4.5.4 Mechanical Stress 566
20.4.5.5 Electrical Stress 566
20.4.5.6 Environmental Stress 567
20.4.6 Miscellaneous Requirements 568
20.4.7 Failure Criteria 568
20.4.8 USCAR-33 Requirement 569
20.5 Conclusion and Next Steps 570
20.6 Summary and Outlook 570
References 570
Chapter 21: Lightning Effects on LED-Based Luminaires 572
21.1 Introduction 572
21.2 Mechanism of Lightning Propagation 573
21.3 Effects of Lightning on LEDs and Basic Mitigation Method 575
21.3.1 Effects of Lightning 575
21.3.2 Basic Mitigation 575
21.4 Lightning Studies on Outdoor LED-Based Luminaires 576
21.4.1 Modelling in ATP-EMTP 576
21.4.2 Studies and Simulation 576
21.5 Influence of System Type on Expected Overvoltage Levels 579
21.6 Conclusions 581
References 582
Chapter 22: The Next Frontier: Reliability of Complex Systems 583
22.1 Introduction 583
22.2 All Components Matter 584
22.3 Complex Systems: Availability Rather Than Reliability 585
22.4 Testing and Validation 587
22.5 Software Reliability 588
22.6 Reliability and Data Analytics 590
22.7 Final Remarks 592
References 592
Index 594