Evaluation on multiple layer PBO-based Cu RDL process for Fan-Out Wafer Level Packaging (FOWLP)

Fan-Out Wafer Level Packaging (FOWLP) was proposed and introduced due its advantages in cost reduction [1] and enhanced packaging capabilities. However, there are still many challenges relating to yield loss and manufacturability [1],[2],[3]. In addition, there is also an increasing demand for the Cu Redistribution Layer (RDL) to achieve finer resolution with higher thickness. In this evaluation, we increased the metallization density, to study if the resistance is lowered, in accordance to the changes. In this study, we shall discuss on the minimum feature size resolution, PR and plated contours. Process issues including PBO delamination is discussed. Test vehicles are fabricated employing Fan-Out Wafer Level Packaging (FOWLP) technology with 3 layers of Polybenzoxazole (PBO)-based, Cu RDL then assembled on a PCB test board for brief reliability evaluation. A schematic illustrating the entire fabrication flow using FOWLP approach is as given in Figure. 1.