(311c) Optimal Design and Operation for Environmentally Benign Electroplating

The optimality of design and operation of an electroplating system determines largely coating quality, productivity, and waste reduction efficiency. Industrial practice shows that, in a usual operation, the solution loss from an electroplating unit through drag-out can be as high as 30% of overall consumption. This has dramatically increased operating cost as well as waste treatment cost. On the other hand, plating quality in terms of coating thickness on workpieces is always a concern in plants. To address these economic and environmental issues, Xu et al. (2005) have proposed a general integrated system modeling methodology for characterizing the dynamic behavior of a closed-loop plating-rinsing system that can recover very effectively the lost chemical/metal-containing solution from the plating unit due to drag-out. However, the operational opportunities in this work, such as the optimal settings of various chemical concentrations during the electroplating process, are ignored.

This paper presents a new fundamental-based modeling and solving methodology to advance current studies. The model has integrated both electroplating and rinse dynamics and can simultaneously identify the design, operation, and control optimality for electroplating and rinsing system. To efficiently solve the derived mixed-integer dynamic optimization (MIDO) model, orthogonal collocation method is employed to transform the MIDO model to a mixed-integer nonlinear programming (MINLP) model. A case study on an alkali zinc electroplating system will demonstrate the efficacy of the developed methodology.