Metal Finishing Guide Book

2012-2013

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Table VI. Copper Pyrophosphate Bath for General Use Copper pyrophosphate (Cu2P2O7��3H2O) Potassium pyrophosphate (K4P2O7) Potassium nitrate Concentrated ammonium hydroxide pH Temperature Current density 52.5-84.0 g/L (7.0-11.2 oz/gal) 201.1-349.1 g/L (26.8-46.5 oz/gal) 3.0-6.0 g/L 3.75-11.0 ml/L 8.0-8.7 43-60OC (110-140��F) 1.0-8.0 A/dm2 (10.0-80.0 A/ft2) Agitation Mechanical and air Filtration Continuous Operating parameters by analysis are: Copper metal 18.8-30.0 g/L (2.5-4.0 oz/gal) Pyrophosphate 131.6-225.0 g/L (17.5-30.0 oz/gal) P2O7/Cu ratio 7.0:1-7.5:1 copper, on steel and zinc die castings, and cause poor adhesion. A cyanide- or pyrophosphate-copper strike is used for steel, and a cyanide strike for zinc is recommended. The pyrophosphate-copper strike is a diluted version of the plating bath, which can have a P2O7/Cu ratio of 10:1 or higher. A typical formulation would be as shown in Table V. Typical Pyrophosphate Bath The copper pyrophosphate bath formulation in Table VI can be used for all plating applications except printed circuits. Current interruption or periodic reverse current can further refine the grain structure. Printed Circuit Bath The use of nonproprietary or proprietary additives that improve the throwing power and ductility of deposit is recommended for printed circuit application. A typical formulation is shown in Table VII. Copper pyrophosphate baths are sensitive to contamination, especially organic conTable VII. Copper Pyrophosphate for Printed Circuits Copper pyrophosphate (Cu2P2O7��3H2O) Potassium pyrophosphate (K4P2O7) Potassium nitrate Concentrated ammonium hydroxide Addition agent pH Temperature Current density Agitation 57.8-73.3 g/L (7.7-9.8 oz/gal) 231.0-316.5 g/L (30.8-42.2 oz/gal) 8.2-15.8 g/L (1.1-2.1 oz/gal) 2.7-7.5 ml/L (0.3-0.75% by volume) As required 8.0-8.4 49-54��C (120-130��F) 2.5-6.0 A/dm2 (25.0-60.0A/ft2) Mechanical and air Operating parameters by analysis are: Copper metal 20.7-26.2 g/L (2.75-3.5 oz/gal) Pyrophosphate 150.0-204.4 g/L (20.0-27.2 oz/gal) P2O7/Cu ratio 7.2:1-7.8:1 318

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