Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Page 618 of 707

A typical process sequence for nickel, gold stripe, and solder plating is shown in Figure 8. PLATING SOLUTIONS As indicated earlier, the solutions used for reel-to-reel plating usually contain the same constituents as those used for other types of plating. To convert them to high-speed processes, the metal concentration and that of some of the other con- stituents are increased and such operating conditions as temperature and pH are modified to produce improved deposits at higher current densities. Proprietary high-speed solutions tailored for reel-to-reel plating are avail- able from a number of plating process supply companies. The properties of the deposits have been engineered to meet the critical requirements of the elec- tronics industry and the operation of the solutions is kept fairly simple to enable good control. Solution formulas found elsewhere in this Guidebook can serve as the basis for solutions to be used for reel-to-reel plating. High efficiency solutions for cop- per, nickel sulfamate, and silver are described that can be run with the concen- trations shown. For the standard formulas, however, increasing the metal content from 25 to 50%, possibly with similar increases in the main conducting salts, may be necessary to reach the current densities required for optimum production rates. Adjustments to the pH and operating at higher than specified temperatures also may be required. TANK DIMENSIONS The width and depth of the processing tanks for a reel-to-reel plating line depend on the size, shape, and number of strips to be plated. When anodes are required, or cathodes in the case of anodic current, they should be positioned as close to the strip(s) as possible, but not so close that shorting can occur. A space of 2-4 in. is gen- erally used. Fig. 8. Typical process for nickel plating, gold striping, and solder plating a stamped connector contact. 617

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