The Mechanics of Solder Alloy Wetting and Spreading

In 1992 Congress passed the Defense Manufacturing Engineering Education Act with the intent of encouraging academic institutions to increase their emphasis on manufacturing curricula. The need for this incentive to integrate the academic and industrial communities was clear: gaps in manufacturing science were inhibiting the evolution of new manufacturing technologies that are required for the U.S. to maintain a competitive posture in the world marketplace. The Army Research Laboratory and Sandia National Laboratories sought to contribute to the congressional intent by initiating a new series of graduate level college textbooks. The goal was to focus next-generation scientists onto issues that were common to the needs of the commercial market, the affordability of DoD weapons systems, and the mobilization readiness of the U.S. Armed Forces. The textbook The Mechanics of Solder Wetting and Spreading was written in this spirit by nationally renowned scientists for academe and industry. Research ers using the book are encouraged to formulate programs that will establish scien tific correlations between manufacturing process controls and product reliability. Such correlations are essential to the building of a new electronics industry which is based upon the futuristic concepts of Virtual Factories, Prototyping, and Testing.

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1. Introduction: The Mechanics of Solder Alloy Wetting and Spreading.- 1.1 Soldering in Electronics.- 1.2 The Wetting Problem.- References.- 2. Solderability Testing.- 2.1 Introduction.- 2.2 The Numbers Problem.- 2.3 The Consistency Problem.- 2.4 The Requirements Problem.- 2.5 The Aging Problem.- 2.6 Conclusions.- 2.7 Appendix.- References.- 3. Fluxes and Flux Action.- 3.1 Introduction.- 3.2 Flux History.- 3.3 Flux Requirements.- 3.4 Rosin-Based Fluxes.- 3.5 Gaseous Fluxes.- 3.6 Inorganic Fluxes.- 3.7 Effect of Solder Impurities on Solderability.- 3.8 Solderability Tests.- References.- 4. Reactive Wetting and Intermetallic Formation.- 4.1 Introduction.- 4.2 Analysis of Solder Spreading Kinetics.- 4.3 Contact Line Motion Over Obstacles.- 4.4 Metallurgy of the Moving Contact Line.- 4.5 Thermodynamic Calculation of the Ternary Pb-Sn-Cu System.- 4.6 Wetting Balance Studies on Cu6sn5 and Cu3Sn.- 4.7 Conclusion.- 4.8 Acknowledgments.- References.- 5. Loss of Solderability and Dewetting.- 5.1 Introduction.- 5.2 Characterization of Dewetting.- 5.3 Wetting Stability Diagrams.- 5.4 Dynamics of Wetting Instabilities: Physical Mechanisms.- 5.5 Intermetallic Formation.- 5.6 Conclusions.- 5.7 Acknowledgments.- References.- 6. Oxidation of Solder Coatings.- 6.1 Introduction.- 6.2 Tin-Lead-Copper System Metallurgy.- 6.3 Role of Oxides in Solderability Loss.- 6.4 Tin-Lead Oxidation.- 6.5 Solderability Assessment Via Oxides.- 6.6 Accelerated Aging.- 6.7 Future Directions.- References.- 7. Surface and Interface Energy Measurements.- 7.1 Abstract.- 7.2 Introduction.- 7.3 Basic Concepts.- 7.4 Equilibrium Conditions for a Curved Interface.- 7.5 Capillarity Effect in Solids.- 7.6 Experimental Techniques.- 7.7 Conclusions.- 7.8 Acknowledgments.- References.- 8. Advanced SolderingProcesses.- 8.1 Impetus for Change.- 8.2 Alternative Approaches to Promote Wetting.- 8.3 Alternate Heat Sources.- 8.4 Solder Bump Technology.- 8.5 Future Directions for Solder Process Technology.- 8.6 Acknowledgments.- References.- 9.0 Reliability-Related Solder Joint Inspection.- 9.1 Abstract.- 9.2 Motivation.- 9.3 Inspection Criteria.- 9.4 Inspection Technologies.- 9.5 Mantech/ADSP Solder Joint Inspection Example.- 9.6 Inspection Automation.- 9.7 Advanced Solder Joint Inspection Techniques.- 9.8 Conclusions.- References.- 10. The Properties of Composite Solders.- 10.1 Introduction.- 10.2 Mechanics of Solder Joints.- 10.3 Alloy Design for Thermomechanical Fatigue Resistance.- 10.4 Methods of Producing Composite Solder Alloys.- 10.5 In-Situ Composite Solders by Rapid Solidification.- 10.6 Properties of Composite Solder Alloys.- 10.7 Summary.- References.