I. Introduction
Compared with traditional fan out package, large-size FOMCM has more I/O count, which can be applied in high-end processing chips. However, more layers of RDL can lead to warpage and die shift as well as the control and improvement of yield. With the increasing requirements of more high-end products, the substrate manufacture have met their bottle-neck. Meanwhile, the requirements of this chain lead to the lack of high-end substrate and capacity. Moreover, due to the needs of the increasing of I/O counts and large-size FOMCM, Chip first encounters its great challenges in yield control. in this paper, we are reducing the chip loss by using chip last technology and converting a high-density substrate from 9-2-9 layers to 3-2-3 layers by adding high-density RDL layer from 3 layers to 5 layers.