Preface ��

About the Authors ����

1 LEDs for Solid-State Lighting 1
1.1 Introduction 1
1.2 Evolution of Light Sources and Lighting Systems 1
1.3 Historical Development of LEDs 6
1.4 Implementation of White Light Illumination with an LED 8
1.5 LEDs for General Lighting 10
References 12

2 Packaging of LED Chips 15
2.1 Introduction 15
2.2 Overall Packaging Process and LED Package Types 16
2.2.1 PTH LED Component 17
2.2.2 SMD LED Component 18
2.3 Chip Mounting and Interconnection 20
2.3.1 Die Attach Adhesive 21
2.3.2 Soldering and Eutectic Bonding 24
2.3.3 Wire Bonding 31
2.3.4 Flip-Chips 34
2.4 Phosphor Coating and Dispensing Process 38
2.4.1 Dispersed Dispensing 39
2.4.2 Conformal Coating 41
2.4.3 Remote Phosphor 45
2.5 Encapsulation and Molding Process 48
2.5.1 Encapsulant Filling with Lens 48
2.5.2 Lens Molding 48
2.6 Secondary Optics and Lens Design 50
References 54

3 Chip Scale and Wafer Level Packaging of LEDs 61
3.1 Introduction 61
3.2 Chip Scale Packaging 63
3.3 Enabling Technologies for Wafer Level Packaging 66
3.3.1 Photolithography 66
3.3.2 Wafer Etching 68
3.3.3 TSV Filling 73
3.3.4 Bond Pad Metallization 73
3.3.5 Wafer Level Phosphor Deposition Methods 76
3.3.6 Moldless Encapsulation 87
3.4 Designs and Structures of LED Wafer Level Packaging 91
3.4.1 Reflective Layer Design 91
3.4.2 Cavity and Reflective Cup by Wet Etching 92
3.4.3 Copper-Filled TSVs for Vertical Interconnection and Heat Dissipation 95
3.5 Processes of LED Wafer Level Packaging 96
3.5.1 Case 1: Multichip LED WLP with Through Silicon Slots 96
3.5.2 Case 2: LED WLP with a Cavity 99
3.5.3 Case 3: Applications of an LED WLP Panel 103
References 106

4 Board Level Assemblies and LED Modules 111
4.1 Introduction 111
4.2 Board Level Assembly Processes 112
4.2.1 Metal Core Printed Circuit Board 112
4.2.2 Printed Circuit Board with Thermal Vias 119
4.2.3 Wave Soldering 124
4.2.4 Surface Mount Reflow 126
4.3 Chip-on-Board Assemblies 130
4.4 LED Modules and Considerations 137
References 141

5 Optical, Electrical, and Thermal Performance 145
5.1 Evaluation of Optical Performance 145
5.1.1 Basic Concepts of Radiometric and Photometric 145
5.1.2 Irradiance Measurement Calibration 155
5.1.3 Common Measurement Equipment 156
5.2 Power Supply and Efficiency 159
5.2.1 Electrical Characteristics of LED 159
5.2.2 Power Supply for LEDs 161
5.2.3 Power Efficiency 162
5.3 Consideration of LED Thermal Performance 163
5.3.1 Thermal Characterization Methods for LEDs 163
5.3.2 Thermal Management Methods 170
References 172

6 Reliability Engineering for LED Packaging 175
6.1 Concept of Reliability and Test Methods 175
6.1.1 Reliability of Electronic Components or Systems 175
6.1.2 Common Failure Mechanisms and Reliability Tests 176
6.2 Failure Analysis and Life Assessment 181
6.2.1 Methodology for Failure Analysis 181
6.2.2 Weibull Analysis and Acceleration Model for Life Assessment 182
6.3 Design for Reliability 185
References 187

7 Emerging Applications of LEDs 189
7.1 LEDs for Automotive Lighting 189
7.1.1 Development 189
7.1.2 Typical Structures 190
7.1.3 Challenges 191
7.1.4 Conclusion 194
7.2 Micro- and Mini-LED Display 194
7.2.1 Development 195
7.2.2 Typical Structures 200
7.2.3 Challenges 202
7.2.4 Conclusion 203
7.3 LED for Visible Light Communication 203
7.3.1 Development 204
7.3.2 Typical Applications 205
7.3.3 Challenges 206
7.3.4 Conclusion 208
References 208

8 LEDs Beyond Visible Light 213
8.1 Applications of UV LED 213
8.1.1 Structures 213
8.1.2 Applications 218
8.1.3 Challenges 222
8.1.4 Conclusion 224
8.2 Applications of IR-LEDs 225
8.2.1 Structures 226
8.2.2 Applications 227
8.2.3 Challenges 231
8.2.4 Conclusion 232
8.3 Future Outlook and Other Technology Trends 233
8.3.1 Better Light Sources 233
8.3.2 Interconnection 234
8.3.3 Interaction with Humans 234
8.3.4 Light on Demand 235
References 235

Index 243