This paper presents for the first time an organic Liquid Crystal Polymer (LCP) based system-on-package (SOP) module for a W-band CMOS power amplifier. The integrated circuit is flip-chipped and fully encapsulated into an all-LCP platform through construction of a cavity to host the chip. Additionally, a matching network is designed and implemented to improve broadband performance of the return loss and gain in the packaged die. Results show the encapsulated flip-chip package is attributed for 1.5 dB of loss in peak amplifier gain and only a slight degradation in return loss. Utilization of a matching network increased the packaged chip gain by 1.1 dB and significantly improved the return loss. This fully encapsulated packaged W-band 45-nm SOI CMOS PA achieves 5.0 dBm output power at 6.0 dB power gain and 5.2% PAE at 90 GHz with 1.0 V supply. To the best of the authors' knowledge, this is the highest performance demonstrated for a W-band CMOS PA on SOP module. Index Terms -CMOS integrated circuits, flip chip, integrated circuit packaging, liquid crystal polymer (LCP), organic materials, power amplifiers.