Issues related to the implementation of Pb-free electronic solders in consumer electronics |
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Authors: | D R Frear |
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Affiliation: | (1) Freescale Semiconductor, Temple, AZ, USA |
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Abstract: | Consumer electronic applications are the primary target of the Pb-free initiative and package assembly and performance is
affected by the move from eutectic Sn–Pb to Pb-free solder alloys. This paper outlines the key issues and mitigation possibilities
for package assembly using Pb-free solders: High temperature reflow, Interfacial reactions, and Reliability. At the high temperatures
required to reflow Pb-free alloys, moisture absorbed into the package can result in delamination and failure. The reaction
of the Pb-free solder with Ni and Cu metallizations results in interfacial intermetallics that are not significantly thicker
than with Sn–Pb but provide a path for fracture under mechanical loading due to the increased strength of the Pb-free alloys.
The reliability issues discussed include thermomechanical fatigue, mechanical shock, electromigration and whiskering. The
Pb-free alloys tend to improve thermomechanical fatigue and electromigration performance but are detrimental to mechanical
shock and whiskering. Design trade-offs must be made to successfully implement Pb-free alloys into consumer applications. |
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