Electrical evaluation of wafer level fan out (WLFO) package using organic substrates for microwave applications

In this paper, developments of wafer level fan-out (WLFO) technology using organic substrates, ajinomoto build-up film (ABF) with laser ablation process and buried pattern PCB, are introduced for low cost and high electrical performance not only on low frequency ranges but also microwave applications. WLFO technology using organic substrates can enhance routing density and provide smaller form factor than flip-chip chip scale packages (fcCSP). Moreover, short signal routing paths from die out to package out can be realized to improve overall electrical performance in WLFO, In this paper, the process of WLFO using ABF with laser drilling and buried-pattern PCB substrate are explained. In addition, measurements of coplanar waveguide (CPW) structure on WLFO and interconnection models from die I/O pad to balls using 3D EM simulation are conducted to estimate effectiveness in microwave ranges.