Lead-free Solders: Materials Reliability for Electronics -- Contents -- Series Preface -- Preface -- List of Contributors -- Thematic Area I: Introduction -- 1 Reliability of Lead-Free Electronic Solder Interconnects: Roles of Material and Service Parameters -- 1.1 Material Design for Reliable Lead-Free Electronic Solders Joints -- 1.2 Imposed Fields and the Solder Joint Responses that Affect Their Reliability -- 1.3 Mechanical Integrity -- 1.4 Thermomechanical Fatigue (TMF) -- 1.5 Whisker Growth -- 1.6 Electromigration (EM) -- 1.7 Thermomigration (TM) -- 1.8 Other Potential Issues -- Thematic Area II: Phase Diagrams and Alloying Concepts -- 2 Phase Diagrams and Their Applications in Pb-Free Soldering -- 2.1 Introduction -- 2.2 Phase Diagrams of Pb-Free Solder Systems -- 2.3 Example of Applications -- 2.3.1 General Applications (Melting, Solidification, Interfacial Reactions) -- 2.3.2 Effective Undercooling Reduction (Co Addition) -- 2.3.3 Unexpected Compound Formation (Sn-Ag/Cu Interfacial Reactions) -- 2.3.4 Unexpected Growth Rates (Sn-Bi/Fe and Sn-Pb/Fe) -- 2.3.5 Unexpected Melting of Solder (Sn-Sb/Ag) -- 2.3.6 Up-Hill Diffusion (Sn-Cu/Ni) -- 2.3.7 Limited Sn Supply (Au/Sn/Cu) -- 2.4 Conclusions -- Acknowledgments -- References -- 3 Phase Diagrams and Alloy Development -- 3.1 Introduction -- 3.2 Computational Thermodynamics as a Research Tool -- 3.2.1 Concept of the Calculation of Phase Diagrams for Multicomponent Systems -- 3.2.2 Modelling of the Gibbs Energy of the System -- 3.2.3 Critical Assessment of Thermodynamic Properties -- 3.3 Thermodynamic Databases - the Underlying Basis of the Modelling of Phase Diagrams and Thermodynamic Properties, Databases for Lead-Free Solders -- 3.3.1 Creation of the Thermodynamic Databases -- 3.3.2 Three Conditions of Consistency.

3.3.3 Specialized Databases for the Modelling of Thermodynamic Properties of Systems Relevant for Lead-Free Solders -- 3.4 Application of the SOLDERS Database to Alloy Development -- 3.4.1 Modelling of Phase Diagrams and Thermodynamic Properties -- 3.4.2 Modelling of Other Properties -- 3.5 Conclusions -- References -- 4 Interaction of Sn-based Solders with Ni(P) Substrates: Phase Equilibria and Thermochemistry -- 4.1 Introduction -- 4.2 Binary Phase Equilibria -- 4.2.1 Literature Overview -- 4.2.2 New Experimental Results -- 4.3 Ternary Phase Equilibria Ni-P-Sn -- 4.3.1 Literature Overview -- 4.3.2 Experimental Results -- 4.4 Thermochemical Data -- 4.4.1 Literature Overview -- 4.4.2 New Experimental Results -- 4.5 Relevance of the Results and Conclusion -- Acknowledgments -- References -- Thematic Area III: Microalloying to Improve Reliability -- 5 'Effects of Minor Alloying Additions on the Properties and Reliability of Pb-Free Solders and Joints' -- 5.1 Introduction -- 5.2 Controlling Ag3Sn Plate Formation -- 5.3 Controlling the Undercooling of Sn Solidification -- 5.4 Controlling Interfacial Reactions -- 5.4.1 Dissolution of UBM and Surface Finishes -- 5.4.2 Cu-Sn Intermetallic Formation -- 5.4.3 Interfacial Void Formation -- 5.4.4 Spalling of Ni-Sn Intermetallics -- 5.5 Modifying the Microstructure of SAC -- 5.6 Improving Mechanical Properties -- 5.6.1 Strength and Hardness -- 5.6.2 Drop Impact Resistance -- 5.6.3 Thermal Fatigue Resistance -- 5.7 Enhancing Electromigration Resistance -- 5.8 Summary -- References -- 6 Development and Characterization of Nano-composite Solder -- 6.1 Introduction -- 6.2 Nano-composite Solder Fabrication Process -- 6.2.1 Nano-particle Fabrication -- 6.2.2 Nano-composite Solder Fabrication -- 6.3 Microstructure -- 6.3.1 Grain Size -- 6.3.2 IMC Layer -- 6.4 Physical Properties -- 6.4.1 Viscosity.

6.4.2 Melting Point -- 6.4.3 Wettability -- 6.4.4 CTE -- 6.4.5 Density and Young's Modulus -- 6.5 Mechanical Properties -- 6.5.1 Microhardness -- 6.5.2 Creep Resistance -- 6.5.3 Mechanical Strength -- 6.5.4 Ductility -- 6.6 Challenges and Solutions -- 6.7 Summary -- Acknowledgments -- References -- Thematic Area IV: Chemical Issues Affecting Reliability -- 7 Chemical Changes for Lead-Free Soldering and Their Effect on Reliability -- 7.1 Introduction -- 7.2 Soldering Fluxes and Pastes -- 7.3 Cleaning -- 7.4 Laminates -- 7.5 Halogen-Free Laminates -- 7.5.1 Z-axis CTE -- 7.5.2 Interconnect Stress Test (IST) -- 7.5.3 Time to Delamination -- 7.5.4 Temperature to Decomposition -- 7.6 Conductive Anodic Filament (CAF) Formation -- 7.7 Summary -- References -- Thematic Area V: Mechanical Issues Affecting Reliability -- 8 Influence of Microstructure on Creep and High Strain Rate Fracture of Sn-Ag-Based Solder Joints -- 8.1 Introduction -- 8.2 Coarsening Kinetics: Quantitative Analysis of Microstructural Evolution -- 8.2.1 Experimental Procedure -- 8.2.2 Results and Discussion -- 8.3 Creep Behavior of Sn-Ag-Based Solders and the Effect of Aging -- 8.3.1 Experimental Procedure -- 8.3.2 Results and Discussion -- 8.4 Role of Microstructure on High Strain Rate Fracture -- 8.4.1 Experimental and Analytical Procedure -- 8.4.2 Results and Discussion -- 8.5 Summary and Conclusions -- Acknowledgments -- References -- 9 Microstructure and Thermomechanical Behavior Pb-Free Solders -- 9.1 Introduction -- 9.2 Sn-Pb Solder -- 9.3 Pb-Free Solders -- 9.3.1 Pb-Free Solders Microstructure -- 9.3.2 Interfacial Intermetallic Formation of Pb-Free Solders -- 9.3.3 Mechanical Metallurgy of Pb-Free Solder Alloys -- 9.3.4 Thermomechanical Fatigue Behavior of Pb-Free Solder Alloys -- 9.4 Summary -- References -- 10 Electromechanical Coupling in Sn-Rich Solder Interconnects.

10.1 Introduction -- 10.2 Experimental -- 10.3 Results -- 10.3.1 Surface Morphology of Sn-3.5Ag-0.7Cu Interconnects after Electromigration -- 10.3.2 Surface Morphology of Pure Sn Interconnect after Electromigration -- 10.3.3 Surface Morphology of Single-Crystal Sn Interconnect after Electromigration -- 10.3.4 Tensile Strength of Solder Interconnects after Electromigration -- 10.3.5 Stress-Relaxation Behavior of Solder Interconnects after Electromigration -- 10.4 Discussion -- 10.4.1 Stress Induced by Vacancy Concentration at the Grain Boundary -- 10.4.2 Compression Stress Induced by the Cu6Sn5 Formation on the Surface -- 10.4.3 Vacancy-Concentration Distribution after Current Stressing -- 10.4.4 Effect of High Vacancy Concentration on Strength -- 10.4.5 Effect of High Vacancy Concentration on Stress-Relaxation Rate -- 10.5 Conclusions -- Acknowledgments -- References -- 11 Effect of Temperature-Dependent Deformation Characteristics on Thermomechanical Fatigue Reliability of Eutectic Sn-Ag Solder Joints -- 11.1 Introduction -- 11.2 Experimental Details -- 11.2.1 Test-Specimen Preparation -- 11.2.2 Thermal Cycling -- 11.2.3 Microstructural Characterization -- 11.2.4 Mechanical Testing -- 11.3 Results and Discussion -- 11.3.1 Effects of Temperature -- 11.3.2 Effects of Strain Rate -- 11.3.3 Influence of Temperature Regime of TMF on the Residual Mechanical Properties -- 11.3.4 Effect of Temperature Regime of TMF on Surface-Damage Accumulation -- 11.3.5 Evolution of Microstructural Damages during Low-Temperature Regime TMF -- 11.4 Summary and Conclusions -- References -- Thematic Area VI: Whisker Growth Issues Affecting Reliability -- 12 Sn Whiskers: Causes, Mechanisms and Mitigation Strategies -- 12.1 Introduction -- 12.2 Features of Whisker Formation -- 12.3 Understanding the Relationship between IMC Growth, Stress and Whisker Formation.

12.4 Summary Picture of Whisker Formation -- 12.5 Strategies to Mitigate Whisker Formation -- 12.6 Conclusion -- Acknowledgments -- References -- 13 Tin Whiskers -- 13.1 Low Melting Point Metals and Whisker Formation -- 13.2 Room-Temperature Tin Whiskers on Copper Substrate -- 13.3 Thermal-Cycling Whiskers on 42 Alloy/Ceramics -- 13.4 Oxidation/Corrosion Whiskers -- 13.5 Mechanical-Compression Whiskers in Connectors -- 13.6 Electromigration Whiskers -- 13.7 Whisker Mitigation -- 13.8 Future Work -- References -- Thematic Area VII: Electromigration Issues Affecting Reliability -- 14 Electromigration Reliability of Pb-Free Solder Joints -- 14.1 Introduction -- 14.2 Failure Mechanisms of Solder Joints by Forced Atomic Migration -- 14.2.1 EM -- 14.2.2 TM -- 14.3 IMC Growth -- 14.3.1 Under Thermal Aging -- 14.3.2 Under Current Stressing -- 14.4 Effect of Sn Grain Structure on EM Reliability -- 14.5 Summary -- Acknowledgments -- References -- 15 Electromigration in Pb-Free Solder Joints in Electronic Packaging -- 15.1 Introduction -- 15.2 Unique Features for EM in Flip-Chip Pb-Free Solder Joints -- 15.2.1 Serious Current-Crowding Effect -- 15.2.2 Joule Heating and Nonuniform Temperature Distribution During EM -- 15.2.3 Effect of Current Crowding and Joule Heating on EM Failure -- 15.2.4 Thermomigration in Solder Joints -- 15.3 Changes of Physical Properties of Solder Bumps During EM -- 15.3.1 Electrical Resistance -- 15.3.2 Temperature Redistribution -- 15.3.3 Mechanical Properties: Electromigration-Induced Brittleness in Solder Joints -- 15.4 Challenges for Understanding EM in Pb-Free Solder Microbumps -- 15.4.1 Fast Dissolution of Cu and Ni under EM -- 15.4.2 Effect of Grain Orientation on Electromigration -- 15.4.3 Stress in Solder Bumps -- 15.5 Thermomigration of Cu and Ni in Pb-Free Solder Microbumps -- 15.6 Summary -- Acknowledgments -- References.

16 Effects of Electromigration on Electronic Solder Joints.