Solders have given the designer of modern consumer, commercial, and military electronic systems a remarkable flexibility to interconnect electronic components. The properties of solder have facilitated broad assembly choices that have fueled creative applications to advance technology. Solder is the electrical and me­ chanical "glue" of electronic assemblies. This pervasive dependency on solder has stimulated new interest in applica­ tions as well as a more concerted effort to better understand materials properties. We need not look far to see solder being used to interconnect ever finer geo­ metries. Assembly of micropassive discrete devices that are hardly visible to the unaided eye, of silicon chips directly to