Fan-out wafer-level packaging (FOWLP), a new heterogeneous integration technology, is gradually becoming an attractive solution. Compared with conventional 2.5D/3D IC structures, fan-out WLP does not use a costly interposer element and can have a thin, high-density, and low-cost IC paAdd additional source...ckaging. In this study, a novel fan-out WLP with RDL-first method is demonstrated. Finite element method was used to optimize the warpage control of a reconstituted wafer and to identify the material properties and fabrication for the FOWLP. Calculation results were applied in the design of the test vehicle. Reliability testing of each component level was performed with different techniques such as temperature cycling test (TCT), high temperature storage (HTS) and thermal humidity storage test (THST). The demonstration of RDL-first WLP technology without interposer proves that it has excellent potential for heterogeneous integration applications.