Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Page 452 of 707

Bath Type Parameters KAu(CN)2 Alkaline gold KCN K2 CO3 or KOH Phosphates/citrates pH Acid cyanide gold KAu(CN)2 Citric acid Cobalt or nickel pH Neutral gold (additive free) KAu(CN)2 KH2 PO4 pH Grain refiners: Tl, As Non-cyanide gold NaAuCl4 Na2 Na2 Na2 SO3 S2 pH NA = not analyzed. Table 4: Analysis of Gold Baths After additions to the tank and adequate mixing, an analysis should be per- formed again to check desired parameters. Normally, well-established plating shops have reasonably good laboratories and are well equipped to keep track of their chemistries. Some job shops depend on analytical support from chemical bath suppliers, which are usually away from site, and they have key parameters analyzed once or twice a month. The drawback of off-site analysis is that bath components cannot be adjusted in a timely manner. Reagent-grade standardized solutions should be procured from a reliable supply house. A well-trained chemist may prepare his own solutions and stan- dardize versus primary standards. The initial receipt date and expiration date of these solutions should be recorded. Deionized or distilled water should used in the analysis. Common standard solutions such as HCl, H2SO4, NaOH, Na2S2O3, AgNO3, I2, K2Cr2O7, KMnO4, and KCSN are available in 0.1-N concentrations. 451 O3 HPO4 Analytical Method AA, ICP, gravimetric Titration, ISE, IC, colorimetry Titration NA Electrode AA, ICP, gravimetric NA AA, ICP Electrode AA, ICP, gravimetric NA Electrode AA, ICP, polarography AA, ICP, gravimetric NA NA NA pH electrode

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