Tu K.-N. Solder Joint Technology: Materials, Properties, and Reliability

Springer, 2007. — 375 p. —The trend in consumer electronic products will be more and more wireless, portable, and handheld. To manufacture these multifunctional products, highdensity circuit interconnections between a Si chip and its substrate are needed. Flip chip solder joint technology, by which an area array of solder bumps is used to join a chip to its substrate, is growing rapidly in demand. Flip chip technology is the only technology that can provide a large number of such interconnections with reliability. Solder joints are ubiquitous in electronic products. There are two themes in this book. The first is the copper–tin reaction as a function of time and temperature, and the second is the effect of external forces on the reaction. Actually the second theme also emphasizes phase transformations under an inhomogeneous boundary condition. Typically, metallurgical phase transformations occur under constant temperature and constant pressure so that Gibbs free energy is minimized. However, in thermomigration or stress migration (creep) of a solder joint, the temperature or the pressure is not constant because there exists a temperature gradient or a stress gradient to drive the phase change, so an equilibrium state with a minimum free energy will not be reached. In electromigration, a potential gradient exists across the sample too. These are irreversible processes. The contents of the book are divided into two parts. Part I, from Chapters 2 to 7, covers copper–tin reactions, and Part II, from Chapters 8 to 12, covers electromigration and thermomigration of solder joints.Introduction of Solder Joint.
Lead-Free Solders.
Solder Joint Technology.
Reliability Problems in Solder Joint Technology.
Future Trends in Electronic Packaging.Copper—Tin Reactions.
Copper-Tin Reactions in Bulk Samples.Wetting Reaction of Eutectic SnPb on Cu Foils.
Wetting Reaction of SnPb on Cu Foil as a Function of Solder Composition.
Wetting Reaction of Pure Sn on Cu Foils.
Ternary Phase Diagram of Sn-Pb-Cu.
Solid-State Reaction of Eutectic SnPb on Cu Foils.
Comparison between Wetting and Solid-State Reactions.
Wetting Reaction of Pb-Free Eutectic Solders on Thick Cu UBM.
Copper—Tin Reactions in Thin-Film Samples.Room-Temperature Reaction in a Bilayer Thin Film of Sn/Cu.
Spalling in Wetting Reaction of Eutectic SnPb on Cu Thin Films.
No Spalling in High-Pb Solder on Au/Cu/Cu-Cr Thin Films.
Spalling in Eutectic SnPb Solder on Au/Cu/Cu-Cr Thin Films.
No Spalling in Eutectic SnPb on Cu/Ni(V)/Al Thin Films.
Spalling in Eutectic SnAgCu Solder on Cu/Ni(V)/Al Thin Films.
Enhanced Spalling Due to Interaction across a Solder Joint.
Wetting Tip Reaction on Thin-Film-Coated V-Grooves.
Copper-Tin Reactions in Flip Chip Solder Joints.Processing a Flip Chip Solder Joint and a Composite Solder Joint.
Chemical Interaction across a Flip Chip Solder Joint.
Enhanced Dissolution of Cu-Sn IMC by Electromigration.
Enhanced Phase Separation in Solder Alloys by Electromigration and Thermomigration.
Thermal Stability of Bulk Diffusion Couples of SnPb Alloys.
Thermal Stress Due to Chip-Packaging Interaction.
Design and Materials Selection of a Flip Chip Solder Joint.
Kinetic Analysis of Flux-Driven Ripening of Copper—Tin Scallops.Morphological Stability of Scallop-Type IMC Growth in Wetting Reactions.
A Simple Model for the Growth of Mono-Size Hemispheres.
Theory of Nonconservative Ripening with a Constant Surface Area.
Size Distribution of Scallops.
Nano Channels between Scallops.
Spontaneous Tin Whisker Growth: Mechanism and Prevention.Morphology of Spontaneous Sn Whisker Growth.
Stress Generation (Driving Force) in Sn Whisker Growth by Cu-Sn Reaction.
Effect of Surface Sn Oxide on Stress Gradient Generation and Whisker Growth.
Measurement of Stress Distribution by Synchrotron Radiation Micro-diffraction.
Stress Relaxation (Kinetic Process) in Sn Whisker Growth by Creep: Broken Oxide Model.
Irreversible Processes.
Kinetics of Grain Boundary Diffusion-Controlled Whisker Growth.
Accelerated Test of Sn Whisker Growth.
Prevention of Spontaneous Sn Whisker Growth.
Solder Reactions on Nickel, Palladium, and Gold.Solder Reactions on Bulk and Thin-Film Ni.
Solder Reactions on Bulk and Thin-Film Pd.
Solder Reactions on Bulk and Thin-Film Au.Electromigration and Thermomigration.
Fundamentals of Electromigration.Electromigration in Metallic Interconnects.
Electron Wind Force of Electromigration.
Calculation of the Effective Charge Number.
Effect of Back Stress on Electromigration and Vice Versa.
Measurement of Critical Length, Critical Product, Effective Charge Number.
Why Is There Back Stress in Electromigration?
Measurement of the Back Stress Induced by Electromigration.
Current Crowding and Current Density Gradient Force.
Electromigration in Anisotropic Conductor of Beta-Sn.
Electromigration of a Grain Boundary in Anisotropic Conductor.
AC Electromigration.
Electromigration in Flip Chip Solder Joints.Unique Behaviors of Electromigration in Flip Chip Solder Joints.
Failure Mode of Electromigration in Flip Chip Solder Joints.
Electromigration in Flip Chip Eutectic Solder Joints.
Electromigration in Flip Chip Composite Solder Joints.
Effect of Thickness of Cu UBM on Current Crowding and Failure Mode.
Electromigration-Induced Phase Separation in Eutectic Two-Phase Solder Alloy.
Polarity Effect of Electromigration on Solder Reactions.Preparation of V-Groove Samples.
Polarity Effect on IMC Growth at the Anode.
Polarity Effect on IMC Growth at the Cathode.
Effect of Electromigration on the Competing Growth of IMC.
Ductile—to-Brittle Transition of Solder Joints Affected by Copper—Tin Reaction and Electromigration.Tensile Test Affected by Electromigration.
Shear Test Affected by Electromigration.
Impact Test.
Drop Test.
Converting a Mini Charpy Impact Machine to Perform Drop Test.
Creep and Electromigration.
Thermomigration.Thermomigration in Flip Chip Solder Joints of SnPb.
Fundamentals of Thermomigration.
Thermomigration and DC Electromigration in Flip Chip Solder Joints.
Thermomigration and AC Electromigration in Flip Chip Solder Joints.
Thermomigration and Chemical Reaction in Solder Joints.
Thermomigration and Creep in Solder Joints.Appendixes:
DifFusivity of Vacancy Mechanism of Diffusion in Solids.
Growth and Ripening Equations of Precipitates.
Derivation of Huntington’s Electron Wind Force.Subject Index.