Development of early process control indicators for reliability drop test performance of eWLB products

Embedded wafer level ball array (eWLB) [1] is well suited to the wide and growing range of mobile applications (mobile phone, smart phone, PDA), therefore reliability drop performance has become an important parameter. Assessing the interconnect quality by means of drop impact testing, during normal production requires considerable efforts (cost and time) and most important lacks fast feedback loop to the process. In addition, eWLB construction issues new challenges due to increase of interconnection types (eg: mold compound to dielectric and die to dielectric). In our research a correlation between the drop impact test and fast ball shear test (FBST) is investigated. Fractures induced during FBST together with fracture energy data were analyzed. Positive correlation was found between fast ball shear results and reliability drop test. These results provide an early and fast process control indicator.