Once the product design is accomplished, based on the functionality and operating environment requirements, the components are assembled onto the printed wiring board (PWB). The choice of the package-to-board interconnection scheme also depends on the performance and reliability requirements of the product. It should be amenable for product upgrades, repair, and reworkability (Behun et al., 1997). Several interconnection materials have been in use and include metallurgical systems such as Sn–Pb, Sn–Bi, Sn–Ag–Cu, etc., and conductive adhesives. Some of these are discussed in some detail to provide the fundamentals and essentials.