NEMI Group Recommends 'Standardized' Lead-Free Solder Alternative
J Bath, C A. Handwerker, E Bradley
Increasing global concern about the environment is bringing regulatory and consumer pressure on the electronics industry in Europe and Japan to reduce or completely eliminate the use of lead in products. As Europe and Japan move toward lead-free electronics, North American electronics manufacturers must prepare to do the same.Among the materials targeted for elimination is lead-contining solder. In 1999, the National Electronics Manufacturing Initiative (NEMI) formed its Lead-Free Task Force with the goal of helping the North American electronics industry develop the capability to produce lead-free products by 2001. The first task of this group was to recommend a standardized lead-free solder alternative. Industry can significantly benefit by focusing on one standard alloy for replacing lead in solder. By cooperatively developing a single solution, it will be possible to implement a replacement sooner, avoid multiple manufacturing processes and enhance basic understanding of the material while assuring its reliability.Earlier this NEMI announced it recommendations for lead-free solder. For relow applications (which represent at least 70 % of all board assembly production), NEMI is recommending use of Sn3.9Ag0.Cu - a predominantly tin-rich alloy with 3.9 % silver and 0.6 % copper. For wave solder production (which requires larger amounts of solder), the group is recommending Sn0.7Cu, a less expensive tin-copper alloy (tin with 0.7 % copper), or - as an alternative standard - Sn3.5Ag (tin with 3.5 % silver).This article will discuss criteria used to select the recommended alloy, the primary alloys that were considered and characteristics of each, and the implications of use of this recommended alternative for the assembly process.