Introduction
Although a package may implement an optimized design, materials, construction and processes, manufacturing variations will occur. In some cases, minor defects may occur as a reflection of this variation that require a focused performance and reliability assessment to determine whether the defect is acceptable. Over the long history of interconnects, voids are considered such a defect [1], [2]. Most solder interconnects in electronic devices are formed with a solidification process; voids may largely be eliminated but some typically remain in various sizes and distribution [3]. Voids in general can be gas-escape related, caused by volume shrinkage or due to external driving forces like current-induced back stress or diffusion.