Solder joints are ubiquitous in electronic consumer products. With the European Union’s directive to ban the use of lead-based (Pb) solders in these products, there is an urgent need for research on solder joint behavior under various driving forces in electronic manufacturing, and for development of lead-free solders. For example, spontaneous Sn whisker growth and electromigration-induced failure in solder joints are serious issues. Analyzing and improving reliability is quite complicated due to the combined effects of electrical, mechanical, chemical, and thermal forces on solder joints. This book thoroughly examines advanced materials reliability issues related to copper-tin reaction and electromigration in solder joints, and presents methods to prevent common reliability problems.