Development of Large RDL Interposer Package: RDL-first FOWLP and 2.5D FO-Interposer

Two types of RDL interposer packages, namely FOWLP and 2.5D FO-interposer have been fabricated with Fan-out packaging technology. Both interposers feature six layers of high-density Cu RDL and are of package size of 52 x 44 mm, accommodating 12 chiplets. These interposers are mounted on a 60 x 60 mm organic substrate. The fabrication process for both RDL interposers is detailed and discussed in this work and comparison is conducted focusing on the interposer warpage. The FOWLP exhibits an initial convex warpage of 213 µm and increases to 380 µm after assembled to organic substrate. In contrast, the 2.5D FO-interposer on organic substrate exhibits a low convex warpage of 36 µm increase to 100 µm after chiplets integration. The 2.5D FO-interposer approach demonstrated better warpage control throughout the assembly process, positioning it as a promising packaging solution that addresses key challenges in interposer technology, particularly in mitigating warpage concerns associated with larger packages.