Lead-Free Electronic Solders, A Special Issue of JOURNAL OF MATERIAL SCIENCES: MATERIALS IN ELECTRONICS
Springer Science, pp. 229-236, 2007
Michael Osterman and Abhijit Dasgupta
University of Maryland
College Park, MD 20742
The transition from lead (Pb) bearing solder to Pb-free solder has arisen in response to government restrictions in the use of lead (Pb) by the European Union. As a result, electronic manufacturers have sought a material comparable the conventional 63Sn37Pb solder that has been traditionally used to assemble electronic hardware. Based on extensive review of various solder combination, the majority of the electronic industry appears to be adopting a tin-silver-copper (SAC) based solder as the Pb-free solder replacement. Significant investments have been made by many researchers to characterize the material behavior and durability of this solder system. While the exact composition of the SAC solder is still in question, it now appears that the 96.5Sn3.0Ag0.5Cu (SAC305) solder is gaining wider acceptance as the favored Pb-free replacement for surface mount assemblies.
This paper presents a review of our current understanding of life expectancy of Pb-free SAC solder interconnects for electronic hardware. To this end, the paper focuses on material characterization of SAC solder, as well as temperature cycling and vibration fatigue reliability. From this review, SAC solder interconnects are shown to be suitable for providing adequate life expectancies in electronic hardware. However, it is clear that there are differences between the conventional Sn37Pb solder that need to be understood in order to design reliability electronic hardware.
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