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

Abstract

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 PWB's, 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 PWB's with conventional and alternative resists and two fully-additive photolithographic microvia PWB fabrication processes.

A Design-Centric Activity-Based Cost Estimation Model for PCB Fabrication

“…However, the cost models for PCB assembly cannot be used for PCB fabrication. The reason is assembly is a discrete process while fabrication is a batch process that utilizes many chemical processing steps [22].…”

“…Consequently, the cost estimation is done after layout and routing. An activity-based cost model is developed by Sandborn and Murphy [22] with an emphasis on the materials. They call it a materialcentric approach and consider the costs of the materials added to, subtracted from, and consumed by PCB fabrication.…”

“…The materials are classified as either materials added or materials consumed by the cost center [22]. Materials added include the copper-clad laminate in inner layer process, the prepreg in lamination, the copper during outer-layer processing, and the soldermask.…”

“…The cost of area materials added is calculated as the product of the cost per unit area, the area of the material, and the number of panels required [22]. The material area is equal to the panel area for the copperclad laminate and photoresist.…”

Experimental and numerical investigation of microvia reliability

“…The choice of PID material and its processing parameters play an important role in the yield and the reliability of the fabricated microvias and HDW structures. [4]. The microvias were fabricated on a double-sided high-Tg FR4 board with a PID material with two metal interconnect layers on each side using the sequential build-up (SBU) process, as shown in the schematic in Figure 2.…”