Material-centric modeling of PWB fabrication: an economic and environmental comparison of conventional and photovia board fabrication processes

This paper presents an activity-based cost model for printed wiring board (PWB) fabrication in which the process steps are defined by material processing activities. The model is designed to be used during system planning and tradeoff analysis prior to physical design. In many activity-based manufacturing cost models, activities are based on equipment and facilities ("equipment-centric"). In the present model, the process steps are based on material processing activities ("material-centric"). Equipment-centric models are appropriate for integrated circuit (IC) manufacture where the processing cost is driven by facilities and equipment; however, in PWB manufacturing, where a significant portion of the cost is materials, it is more appropriate to focus the process modeling around material activities. The models presented in this paper compute the volume of materials used and wasted by the activities associated with the fabrication of PWBs, and in turn, use the computed volumes as inputs for predicting fabrication and waste disposition costs. Activities included in the model are open- and closed-loop plating, coating, etching, stripping, desmearing, plasma etching, lamination, drilling, filling, singulation, and scrapping. Additionally, waste disposition activities that operate on the waste inventory are supported. The models presented here have been integrated into a software tradeoff environment that concurrently performs cost and performance analysis for electronic systems. A tradeoff study is presented that compares the cost and waste associated with fabricating mechanically drilled and plated through-hole PWBs with conventional and alternative resists and two fully-additive photolithographic microvia PWB fabrication processes.