Wafer-Level Flexible 3D Corrugated Interconnect Formation for Scalable In-Mold Electronics with Embedded Chiplets

We have reported a new flexible hybrid electronics (FHE) whose structure is consisting of heterogeneous small/thin/rigid chiplets embedded in 2D molded polymeric substrates such as PDMS and hydrogel on which fine-pitch fanout RDLs are formed by die-first or RDL-first FOWLP. In this study, we apply this FHE methodology to flexible 3D In-Mold Electronics (IME) for highly integrated 3D electronics. 1-mm-square Si chiplets are embedded in PDMS and biocompatible Au RDLs are formed on the elastomer in die-first FOWLP processing, and finally, the resulting 2D FHE (2D-PDMS) is re-molded again to give contact lens-shaped flexible 3D IME (3D-PDMS). In addition, we design the flexible 3D interconnections with self-assembled corrugation of out-of-plane tortuousness by controlling a CTE mismatch between the Au layer and the underneath insulator of flexible epoxy formed on the PDMS.