In this paper, we present the design and development of thin-film liquid-crystal-polymer (LCP) surface-mount packages for Ka-band applications. The packages are constructed using multilayer LCP films and are surface mounted on a printed circuit board (PCB). Our experimental results demonstrate that the package feed-through transition including a PCB launch and bond wires achieve a return loss of better than -20 dB and an insertion loss of less than 0.4 dB around Ka-band. We achieve a measured port-to-port isolation of the package to be more than 45 dB across the Ka-band. We demonstrate the package feed-through circuit model by comparing the simulation of model and bare die measurement data to a packaged amplifier measurement. Finally, we report an LCP cavity that has a measured fine leak rate of 3.6 times 10<sup>-8</sup> atmldrcc/s.