An Alternative to Feed and Bleed for Saving Chemicals and Rinse Water

The feed and bleed method of controlling process chemicals commonly used in the printed circuit industry, though convenient, is inefficient. In a typical feed and bleed application, a portion of the fresh chemistry is always being bled out with the spent solution. A technology introduced by the author's company can achieve the chemical efficiency of a batch method and process convenience of the feed and bleed process. This article describes the technology, application method, theory and mathematical calculation showing the saving. Examples of some of the application areas are: photoresist developing, stripping; ammoniacal etch; electroless copper; rinse water in plating and cleaning.