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Status of the Proliferation of Lead-Free Alloys: 2010

Presenter: Ronald Lasky, Ph.D., P.E.
Company: Indium Corporation
Date Published: 3/4/2010

Description: The EU's RoHS law has driven a significant amount of research to find an alloy for electronic assembly that will satisfy RoHS's lead-free requirement and have optimum assembly process ability and reliability. The resulting research, much of it lead by iNEMI, resulted in the near eutectic tin-silver-copper alloy SAC387 (Sn95.5Ag3.8Cu0.7) as an initial choice to fill this need in the early 2000s. But by 2004 or so, many people were using SAC305, partially because of its greater resistance to tombstoning and lower silver content. It appeared that SAC305 would become the de-facto lead-free standard alloy for RoHS compliant electronic assembly. However, with the dramatic increase in silver prices in the last few years, SAC105, having 2% less silver was being evaluated and used for its obvious cost savings. Reliability testing of SAC105 also showed that although it did not perform as well as SAC305 in thermal fatigue cycle testing, it was better than SAC305 in drop shock tests. The explosive growth of mobile phone sales and other portable electronic devices made this superior drop shock performance attractive for these types of devices.

In addition to research relating to SAC305 and SAC105, much investigation has been performed on the effects of small quantities (<0.1%) of alloying metals on lead-free alloys' process ability and reliability performance. These "dopants" can dramatically affect an alloy's performance.

All of the above work has resulted in what many are calling lead-free alloy proliferation as more and more alloys are being considered for implementation. This proliferation drives up solder paste cost as paste manufacturers cannot achieve economies of scale. In addition, with so many alloys to consider, it is difficult for researchers to develop extensive data bases of process and reliability performance. These new alloys and the introduction of new and miniaturized components, have also resulted in new failure modes such as "graping," and the "head-in-pillow" defect.

This webinar is an overview of this lead-free alloy proliferation, a discussion of these new failure modes and how to minimize them and an outlook on how alloy convergence might occur.

Key Words: 

Lead-Free, Pb-Free, RoHS, alloys, graping, head-in-pillow, SAC305, SAC105

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