Aging effects on microstructure and creep in Sn-3.8Ag-0.7Cu solder

Abstract

Solder joints provide mechanical and electrical interconnections between electronic devices and packaging substrates in electronics applications. The different coefficient of thermal expansion (CTE) between substrate, silicon device and solder imposes strains on the solder joint. Creep constitutes the primary deformation mechanism, limiting the low cycle fatigue life of solder joint. The trend toward miniaturization, higher service temperatures, and higher current densities and the transition to lead-free solders, which possess higher melting points than leaded solders, aggravate the situation. Therefore, the knowledge of properties and performances is needed to be able to predict the lifetime of solders in order to assure successfully applications in electronic assemblies. This study focuses on the change of microstructure due aging in bulk and ball joints, and a preliminary analysis of the primary creep behavior of Sn-3.8Ag-0.7Cu. Differences in microstructure evolution between bulk and small joints are highlighted.