Mitigating Tin Whisker Risks

List of Contributors ix Introduction xi 1 A Predictive Model forWhisker Formation Based on Local Microstructure and Grain Boundary Properties 1 Pylin Sarobol, Ying Wang, Wei-Hsun Chen, Aaron E. Pedigo, John P. Koppes, John E. Blendell and Carol A. Handwerker 1.1 Introduction, 1 1.2 Characteristics of Whisker and Hillock Growth from Surface Grains, 3 1.3 Summary and Recommendations, 17 Acknowledgments, 18 References, 19 2 Major Driving Forces and Growth Mechanisms for TinWhiskers 21 Eric Chason and Nitin Jadhav 2.1 Introduction, 21 2.2 Understanding the Mechanisms Behind Imc-Induced Stress Evolution and Whisker Growth, 24 2.3 Relation of Stress to Whisker Growth, 34 2.4 Conclusions, 39 Acknowledgments, 40 References, 40 3 Approaches of Modeling and Simulation of Stresses in Sn Finishes 43 Peng Su and Min Ding 3.1 Introduction, 43 3.2 Constitutive Model, 44 3.3 Strain Energy Density, 46 3.4 Grain Orientation, 46 3.5 Finite Element Modeling of Triple-Grain Junction, 48 3.6 Finite Element Modeling of Sn Finish with Multiple Grains, 55 References, 66 4 Properties and Whisker Formation Behavior of Tin-Based Alloy Finishes 69 Takahiko Kato and Asao Nishimura 4.1 Introduction, 69 4.2 General Properties of Tin-based Alloy Finishes (Asao Nishimura), 70 4.3 Effect of Alloying Elements on Whisker Formation and Mitigation (Asao Nishimura), 75 4.4 Dependence of Whisker Propensity of Matte Tin-Copper Finish on Copper Lead-Frame Material (Takahiko Kato), 89 4.5 Conclusions, 118 Acknowledgments, 118 References, 119 5 Characterization Techniques for Film Characteristics 125 Takahiko Kato and Yukiko Mizuguchi 5.1 Introduction, 125 5.2 TEM (Takahiko Kato), 125 5.3 SEM (Yukiko Mizuguchi), 140 5.4 EBSD (Yukiko Mizuguchi), 146 5.5 Conclusions, 154 Acknowledgments, 155 References, 155 6 Overview of Whisker-Mitigation Strategies for High-Reliability Electronic Systems 159 David Pinsky 6.1 Overview of Tin Whisker Risk Management, 159 6.2 Details of Tin Whisker Mitigation, 164 6.3 Managing Tin Whisker Risks at the System Level, 173 6.4 Control of Subcontractors and Suppliers, 183 6.5 Conclusions, 185 References, 185 7 Quantitative Assessment of Stress Relaxation in Tin Films by the Formation of Whiskers, Hillocks, and Other Surface Defects 187 Nicholas G. Clore, Dennis D. Fritz, Wei-Hsun Chen, Maureen E. Williams, John E. Blendell and Carol A. Handwerker 7.1 Introduction, 187 7.2 Surface-Defect Classification and Measurement Method, 189 7.3 Preparation and Storage Conditions of Electroplated Films on Substrates, 194 7.4 Surface Defect Formation as a Function of Tin Film Type, Substrate, and Storage Condition, 195 7.5 Conclusions, 209 Appendix, 209 Acknowledgments, 209 References, 213 8 Board Reflow Processes and their Effect on Tin Whisker Growth 215 Jasbir Bath 8.1 Introduction, 215 8.2 The Effect of Reflowed Components on Tin Whisker Growth in Terms of Grain Size and Grain Orientation Distribution, 215 8.3 Reflow Profiles and the Effect on Tin Whisker Growth, 216 8.4 Influence of Reflow Atmosphere and Flux on Tin Whisker Growth, 219 8.5 Effect of Solder Paste Volume on Component Tin Whisker Growth during Electronics Assembly, 220 8.6 Conclusions, 221 Acknowledgments, 222 References, 222 9 Mechanically Induced TinWhiskers 225 Tadahiro Shibutani and Michael Osterman 9.1 Introduction, 225 9.2 Overview of Mechanically Induced Tin Whisker Formation, 227 9.3 Theory, 228 9.4 Case Studies, 237 9.5 Conclusions, 245 References, 246 Index 249