Lead-free Solders
Materials Reliability for Electronics
Wiley Series in Materials for Electronic & Optoelectronic Applications
1. Edition March 2012
520 Pages, Hardcover
Wiley & Sons Ltd
Short Description
Providing a viable alternative to lead-based solders is a major research thrust for the electrical and electronics industries - while mechanically compliant lead-based solders have been widely used in the electronic interconnects, the risks to human health and to the environment are too great to allow continued widescale usage. Presenting a comprehensive understanding of the current state of lead-free electronic interconnects research, this book approaches the ongoing research from fundamental, applied and manufacturing perspectives to provide a balanced view of the progress made and the requirements which still have to be met.
Providing a viable alternative to lead-based solders is a major research thrust for the electrical and electronics industries - whilst mechanically compliant lead-based solders have been widely used in the electronic interconnects, the risks to human health and to the environment are too great to allow continued widescale usage. Lead-free Solders: Materials Reliability for Electronics chronicles the search for reliable drop-in lead-free alternatives and covers:
* Phase diagrams and alloy development
* Effect of minor alloying additions
* Composite approaches including nanoscale reinforcements
* Mechanical issues affecting reliability
* Reliability under impact loading
* Thermomechanical fatigue
* Chemical issues affecting reliability
* Whisker growth
* Electromigration
* Thermomigration
Presenting a comprehensive understanding of the current state of lead-free electronic interconnects research, this book approaches the ongoing research from fundamental, applied and manufacturing perspectives to provide a balanced view of the progress made and the requirements which still have to be met.
Preface xvii
List of Contributors xix
Thematic Area I: Introduction 1
1 Reliability of Lead-Free Electronic Solder Interconnects: Roles of Material and Service Parameters 3
K. N. Subramanian
1.1 Material Design for Reliable Lead-Free Electronic Solders Joints 3
1.2 Imposed Fields and the Solder Joint Responses that Affect Their Reliability 5
1.3 Mechanical Integrity 5
1.4 Thermomechanical Fatigue (TMF) 6
1.5 Whisker Growth 7
1.6 Electromigration (EM) 7
1.7 Thermomigration (TM) 8
1.8 Other Potential Issues 8
Thematic Area II: Phase Diagrams and Alloying Concepts 11
2 Phase Diagrams and Their Applications in Pb-Free Soldering 13
Sinn-wen Chen, Wojciech Gierlotka, Hsin-jay Wu, and Shih-kang Lin
2.1 Introduction 14
2.2 Phase Diagrams of Pb-Free Solder Systems 14
2.3 Example of Applications 23
2.4 Conclusions 39
3 Phase Diagrams and Alloy Development 45
Alan Dinsdale, Andy Watson, Ales Kroupa, Jan Vrestal, Adela Zemanova, and Pavel Broz
3.1 Introduction 45
3.2 Computational Thermodynamics as a Research Tool 48
3.3 Thermodynamic Databases - the Underlying Basis of the Modelling of Phase Diagrams and Thermodynamic Properties, Databases for Lead-Free Solders 51
3.4 Application of the SOLDERS Database to Alloy Development 57
3.5 Conclusions 68
4 Interaction of Sn-based Solders with Ni(P) Substrates: Phase Equilibria and Thermochemistry 71
Clemens Schmetterer, Rajesh Ganesan, and Herbert Ipser
4.1 Introduction 72
4.2 Binary Phase Equilibria 73
4.3 Ternary Phase Equilibria Ni-P-Sn 85
4.4 Thermochemical Data 94
4.5 Relevance of the Results and Conclusion 111
Thematic Area III: Microalloying to Improve Reliability 119
5 'Effects of Minor Alloying Additions on the Properties and Reliability of Pb-Free Solders and Joints' 121
Sung K. Kang
5.1 Introduction 122
5.2 Controlling Ag3Sn Plate Formation 125
5.3 Controlling the Undercooling of Sn Solidification 132
5.4 Controlling Interfacial Reactions 136
5.5 Modifying the Microstructure of SAC 145
5.6 Improving Mechanical Properties 149
5.7 Enhancing Electromigration Resistance 151
5.8 Summary 153
6 Development and Characterization of Nano-composite Solder 161
Johan Liu, Si Chen, and Lilei Ye
6.1 Introduction 162
6.2 Nano-composite Solder Fabrication Process 162
6.3 Microstructure 166
6.4 Physical Properties 167
6.5 Mechanical Properties 169
6.6 Challenges and Solutions 171
6.7 Summary 174
Thematic Area IV: Chemical Issues Affecting Reliability 179
7 Chemical Changes for Lead-Free Soldering and Their Effect on Reliability 181
Laura J. Turbini
7.1 Introduction 181
7.2 Soldering Fluxes and Pastes 181
7.3 Cleaning 185
7.4 Laminates 185
7.5 Halogen-Free Laminates 186
7.6 Conductive Anodic Filament (CAF) Formation 189
7.7 Summary 193
Thematic Area V: Mechanical Issues Affecting Reliability 195
8 Influence of Microstructure on Creep and High Strain Rate Fracture of Sn-Ag-Based Solder Joints 197
P. Kumar, Z. Huang, I. Dutta, G. Subbarayan, and R. Mahajan
8.1 Introduction 198
8.2 Coarsening Kinetics: Quantitative Analysis of Microstructural Evolution 199
8.3 Creep Behavior of Sn-Ag-Based Solders and the Effect of Aging 206
8.4 Role of Microstructure on High Strain Rate Fracture 219
8.5 Summary and Conclusions 227
9 Microstructure and Thermomechanical Behavior Pb-Free Solders 233
D.R. Frear
9.1 Introduction 233
9.2 Sn-Pb Solder 234
9.3 Pb-Free Solders 237
9.4 Summary 248
10 Electromechanical Coupling in Sn-Rich Solder Interconnects 251
Q.S. Zhu, H.Y. Liu, L. Zhang, Q.L. Zeng, Z.G. Wang, and J.K. Shang
10.1 Introduction 252
10.2 Experimental 253
10.3 Results 255
10.4 Discussion 264
10.5 Conclusions 269
11 Effect of Temperature-Dependent Deformation Characteristics on Thermomechanical Fatigue Reliability of Eutectic Sn-Ag Solder Joints 273
Andre Lee, Deep Choudhuri, and K.N. Subramanian
11.1 Introduction 274
11.2 Experimental Details 275
11.3 Results and Discussion 276
11.4 Summary and Conclusions 294
Thematic Area VI: Whisker Growth Issues Affecting Reliability 297
12 Sn Whiskers: Causes, Mechanisms and Mitigation Strategies 299
Nitin Jadhav and Eric Chason
12.1 Introduction 299
12.2 Features of Whisker Formation 303
12.3 Understanding the Relationship between IMC Growth, Stress and Whisker Formation 308
12.4 Summary Picture of Whisker Formation 314
12.5 Strategies to Mitigate Whisker Formation 316
12.6 Conclusion 318
13 Tin Whiskers 323
Katsuaki Suganuma
13.1 Low Melting Point Metals and Whisker Formation 323
13.2 Room-Temperature Tin Whiskers on Copper Substrate 325
13.3 Thermal-Cycling Whiskers on 42 Alloy/Ceramics 326
13.4 Oxidation/Corrosion Whiskers 329
13.5 Mechanical-Compression Whiskers in Connectors 330
13.6 Electromigration Whiskers 331
13.7 Whisker Mitigation 332
13.8 Future Work 334
Thematic Area VII: Electromigration Issues Affecting Reliability 337
14 Electromigration Reliability of Pb-Free Solder Joints 339
Seung-Hyun Chae, Yiwei Wang, and Paul S. Ho
14.1 Introduction 339
14.2 Failure Mechanisms of Solder Joints by Forced Atomic Migration 342
14.3 IMC Growth 351
14.4 Effect of Sn Grain Structure on EM Reliability 363
14.5 Summary 366
15 Electromigration in Pb-Free Solder Joints in Electronic Packaging 375
Chih Chen, Shih-Wei Liang, Yuan-Wei Chang, Hsiang-Yao Hsiao, Jung Kyu Han, and K.N. Tu
15.1 Introduction 376
15.2 Unique Features for EM in Flip-Chip Pb-Free Solder Joints 376
15.3 Changes of Physical Properties of Solder Bumps During EM 386
15.4 Challenges for Understanding EM in Pb-Free Solder Microbumps 393
15.5 Thermomigration of Cu and Ni in Pb-Free Solder Microbumps 394
15.6 Summary 394
16 Effects of Electromigration on Electronic Solder Joints 401
Sinn-wen Chen, Chih-ming Chen, Chao-hong Wang, and Chia-ming Hsu
16.1 Introduction 401
16.2 Effects of Electromigration on Solders 402
16.3 Effects of Electromigration on Interfacial Reactions 408
16.4 Modeling Description of Effects of Electromigration on IMC Growth 414
16.5 Conclusions 418
Thematic Area VIII: Thermomigration Issues Affecting Reliability 423
17 Thermomigration in SnPb and Pb-Free Flip-Chip Solder Joints 425
Tian Tian, K.N. Tu, Hsiao-Yun Chen, Hsiang-Yao Hsiao, and Chih Chen
17.1 Introduction 425
17.2 Thermomigration in SnPb Flip-Chip Solder Joints 427
17.3 Thermomigration in Pb-Free Flip-Chip Solder Joints 432
17.4 Driving Force of Thermomigration 435
17.5 Coupling between Thermomigration and Creep 439
17.6 Coupling between Thermomigration and Electromigration: Thermoelectric Effect on Electromigration 441
17.7 Summary 441
Thematic Area IX: Miniaturization Issues Affecting Reliability 443
18 Influence of Miniaturization on Mechanical Reliability of Lead-Free Solder Interconnects 445
Golta Khatibi, Herbert Ipser, Martin Lederer, and Brigitte Weiss
18.1 Introduction 445
18.2 Effect of Miniaturization on Static Properties of Solder Joints (Tensile and Shear) 448
18.3 Creep and Relaxation of Solder Joints 475
18.4 Summary and Conclusions 478
References 482
Index 487
