Part 7: Lead-free Reliability for Harsh-environment Electronics

摘要

Neither regulations nor legislation drove initial lead-free systematic R&D, rather it was the mission of advancing solder materials above and beyond tin/lead. Before research began, we recognized that any working lead-free alloy for electronics must be tin-based for fundamental scientific reasons. We also found that no binary alloy could fill the role for surface mount soldering. But it was unknown if a ternary system could do the job. As the result of systematic research, in conjunction with verification on production floors, it became clear that a ternary alloy from the groups of Sn/Ag/Bi, Sn/Ag/Cu (SAC), Zn- and Mg-con-taining systems, and many others are unable to maintain the existing manufacturing infrastructure. Consequently, R&D must continue, extending to the higher-element systems — quaternary and pentanary alloys. Production successes by OEMs who are vanguards in lead-free manufacturing also served as the basis for selecting viable lead-free alloys. As a result, a short list of viable alloys are available for various industry applications.