Electrical characterization of wafer level fan-out (WLFO) using film substrate for low cost millimeter wave application

In this paper, development of wafer level fan-out (WLFO) technology using ajinomoto build-up film (ABF) substrate with laser ablation process is introduced for low cost and high electrical performance for millimeter wave application. Wafer level fan-out (WLFO) technology using ABF substrate can enhance routing density and provide smaller form factor with lower parasitic elements than flip-chip chip scale packages (FCCSP). Moreover, short electrical paths from die out to package out can be realized with WLFO, and the low-k ABF material provides good electrical properties for high frequency areas. In this paper, the process of WLFO using ABF substrate with laser drilling is explained and electrical parasitic elements are compared between FCCSP and WLFO using 3D simulation tools. In addition, electrical characterization of coplanar waveguide (CPW) structure and interconnection models from die I/O pad to balls using 3D EM simulation are conducted to estimate effectiveness on millimeter wave range. Actual measurements of CPW structures are also presented.