Self-monitoring electroless plating solution

Abstract

This invention relates to monitoring the concentration of a component dissolved in solution where the component imparts a perceptible color to the solution and varies in concentration with use of the solution. The invention is based upon use of a colorant of a fixed optical density that absorbs light in a different region of the visible spectrum than the monitored component. As the monitored component varies in concentration with use of the solution, the optical density of that component in solution varies as a function of its concentration and consequently, the amount of light, i.e., the intensity of light, passing through the solution will also vary as a function of concentration. Since the optical density of the colorant remains fixed during use, the optical density of the monitored component changes relative to the optical density of the colorant during use of the solution. Because the monitored component and colorant absorb light in different regions of the visible spectrum and their optical densities change relative to each other, there results a perceptible color change as a function of concentration that may be seen visually or measured by instrumentation.

Dependencies are inferred from the claim text.