Development of Large RDL Interposer Package using RDL-first FOWLP Process

In this work, an organic RDL interposer with large package size of 52 x 44 mm consisting of 12 embedded chiplets on a 60 x 60 mm organic substrate has been demonstrated using RDL-first FOWLP process. 2 field masks stitching was used to create the large interposer package size. 6 layers of high-density Cu RDL have been processed to meet the 12 chiplets interconnectivity and bandwidth performance requirements. Chiplets with micro-bumps were assembled on the RDL with a mass reflow process and encapsulated with mold compound thus forming the RDL interposer package. Electrical testing was conducted on the RDL test structures and the chiplets and results show good electrical continuity across the stitched Cu RDL traces and assembled chiplets. Shadow Moiré warpage measurement was performed on the RDL interposer package to characterize the warpage behavior during board assembly. The Shadow Moiré results show a large warpage change associated with the large RDL interposer during reflow process. A TCB technique was used to assemble the RDL interposer to the organic build-up substrate, to reduce the package warpage and enable the assembly of the RDL interposer to the organic substrate.