The inner part of the CMS phase II upgrade outer tracker will be built from PS modules consisting of two closely spaces silicon sensors and associated electronics and mechanics. The sensors must be assembled with a translational (x-y) alignment of approximately 40 um and a rotational alignment of 800 urad. An automated module assembly system is proposed as a method to build these modules on a large production scale. The automated system is based on the integration of a high-precision motion stage with vacuum handling and vision systems. A dedicated software application obtains images, performs pattern recognition to deduce component positions, and controls the motion and vacuum handling systems to precisely position components.