This thesis presents a novel application of the Layered Electrical Product (LEP) model of the PDES (Product Data Exchange specification using STEP) standard. All three levels of the LEP model are developed for a typical microwave module (MWM). The latter is comprised of a component layer, the artwork, an insulation layer and a ground plane, which is a complex mechanical part. The nature of the ground plane necessitated the enhancement of the first level of the model to include three- dimentional topological entities. Consequently, although the artwork and insulation layers are represented in two-and-a-half dimensions, (which is common practice in the case of Printed Wiring Boards), the ground plane is modeled using the three- dimentional PDES Geometrical and Topological models and the Form Features model. Level II includes the electrical entities of the MWM. New conventions that are necessary to represent particular features of the MWM have been proposed and applied. Based on the intention of PDES, design information that is closely related to manufacturing concerns has been represented in Level III of the model. Both the proposed structure and the contents of this level for MWMs are presented. Material specifications, mechanical features and design specifications for the manufacture of joins are included. Finally, potential applications of the LEP model and especially of Level III in automated process planning and producibility assessment are discussed.