Electroplating selective plating

The use of Zn-Cr(III) alloy plating has almost replaced the use of Cr(VI) in the electroplating industry due to its excellent corrosion resistance and its lower toxicity. Recently, a solvent extraction procedure for separating and selectively recovering the two metals, zinc and chromium, from electroplating wastewaters has been demonstrated [10]. 

Copper was selected as the metallizing material because of its wide industrial application. Copper was then plated onto the preplate layer either by electroless or electroplating. A commercial solution was used for the electroless copper plating to obtain a 1.0-pm thick copper deposit. A 20 pm-thick layer of copper was deposited electrolytically under the following conditions. 

Ion chromatographic analysis methods ensure speed and high precision in the analysis of main components as well as of reaction and decomposition products in electroplating baths. The advantage of ion chromatography relative to the partly unspecific wet chemical methods utilized so far lies in the selectivity of the stationary phases and the detection systems being used. Thus, in most cases sample preparation is limited to a simple dilution with de-ionized water and subsequent filtration. A variety of applications on the basis of electrodeposition and electroless plating is summarized in Table 8-3. 

The net result is that metal dissolves from the anode and deposits on the cathode. The phenomenon is the basis of electroplating (e.g., chromium plating of steel), electrowinning, and electrorehning. Also, it is the analytical basis of an electrodeposition method known as electrogravimetry. This involves the separation and weighing of selected components of a sample. Most metal elements can be determined in this manner, usually deposited as the M° species, although some metal elements can be deposited as oxides. The halides can be determined by deposition as the silver halide. Metals commonly determined include Ag, Bi, Cd, Co, Cu, In, Ni, Sb, Sn, and Zn. 

Converting Palladium to Palladium Sulfide. Crimson, invented by Shipley, employs a conversion step after the activator where palladium is changed to palladium sulfide, which is claimed to be more conductive for subsequent electrolytic copper plating. The enhancer stabilizes the conductive film so that it is chemically resistant to imaging steps. The stabilizer neutralizes residues from the enhancer, thereby preventing contamination of subsequent steps. The microetch selectively removes activator from copper surfaces to achieve optimum copper-to-copper bond and reliable dry film adhesion. The process works best in conveyorized horizontal equipment and can be followed by pattern or panel electroplating. (See Fig. 30.3.)... 

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