The fan-out wafer-level packaging market is heating up. With the packaging done on singulated die formed into a reconstituted molded wafer, Fan Out packaging enables multi-die packages, through partitioning with different nodes and functionality. Initially Fan Out was used primarily for smaller, lower I/O count packages, until ASE introduced a very high-density Fan Out alternative to 2.5D Interposer packages, Fan Out Chip on Substrate (FOCoS), a hybrid Fan Out/FCBGA package.
What is Fan Out Chip on Substrate (FOCoS)?
FOCoS is defined as a fan-out package flip-chip mounted on a high pin count ball grid array (BGA) substrate. The fan-out package is constructed from multiple chips with short interconnection between die to die (D2D) by a re-distribution layer (RDL) process, which has the potential for high speed communication and multi-function applications. The fan-out package is treated as if it was a single die and then flip-chip mounted onto the BGA substrate.