Case studies of laser ablation effects on Flash Memory devices

It becomes a trend of replacing Au wire bonds with Cu wire bonds in the plastic IC packages due to the benefit of cost saving and electrical performance. Some plastic packages, such as FGBA package used for Flash Memory devices, utilize a new type of epoxy mold compound with higher reliability. Such mold compound is harder against chemical etching than other mold compounds and poses a greater challenge for failure analysis. The conventional manual acid dripping and automated acid etching do not work for the packages with this “hard” mold compound. Laser ablation is a potential alternative to remove such mold compound for decapsulation purpose, but the process is not straight forward and it must be coupled with appropriate chemical treatment. To establish a working process, four different types of laser decapsulation tools available in the market are evaluated, and only one provides working solution for the decapsulation of this package. In this paper, the evaluation results of four laser decapsulation tools are presented. The best case study result (with optimized laser ablation parameters) compared with the worse case study result (with non-optimized laser ablation parameters) from the same laser tool will also be shared.