Inhomogeneous deformation and microstructure evolution of Sn-Ag-based solder interconnects during thermal cycling and shear testing

0026-2714/$ see front matter 2012 Elsevier Ltd. A doi:10.1016/j.microrel.2012.01.009 ⇑ Corresponding author at: Department of Materi Shenzhen Graduate School, Harbin Institute of Tec China. Tel.: +86 755 26033463; fax: +86 755 260334 E-mail address: [email protected] (M.Y. Li). Orientation imaging microscopy was adopted to characterize the microstructural changes in Sn–Agbased solder interconnects during thermal cycling and shear testing. The deformation and microstructure evolution of Sn–Ag-based solder interconnects are inhomogeneous, depending on the orientations of b-Sn grains in the as-solidified microstructure. Recovery or recrystallization can take place even under pure shear stress at room temperature, and it tends to occur at high-angle grain boundaries in multi-grained solder interconnects, while it localizes in near-interface region in solder interconnects with only one grain inside. During thermal cycling, the hardness of recrystallized microstructure decreased significantly due to the segregation of Ag3Sn IMC particles towards the newly-formed recrystallized boundaries, increasing the ease of localized deformation in this weakened microstructure. As a consequence, cracks were propagated intergranularly in the recrystallized microstructure. 2012 Elsevier Ltd. All rights reserved.