Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Table VI. Copper Pyrophosphate Bath for General Use Copper pyrophosphate (Cu2 P2 Potassium pyrophosphate (K4 Potassium nitrate Temperature Current density Agitation Filtration Operating parameters by analysis are: Copper metal Pyrophosphate /Cu ratio P2 O7 O7 P2 O7 ·3H2 ) Concentrated ammonium hydroxide pH O) 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 43-60O C (110-140° 1.0-8.0 A/dm2 F) (10.0-80.0 A/ft2 Mechanical and air Continuous 18.8-30.0 g/L (2.5-4.0 oz/gal) 131.6-225.0 g/L (17.5-30.0 oz/gal) 7.0:1-7.5:1 be as shown in Table V. 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 rec- ommended. The pyrophosphate-copper strike is a diluted version of the plating bath, which can have a P2 O7 /Cu ratio of 10:1 or higher. A typical formulation would Typical Pyrophosphate Bath The copper pyrophosphate bath formulation in Table VI can be used for all plat- ing applications except printed circuits. Current interruption or periodic reverse cur- rent can further refine the grain structure. Printed Circuit Bath The use of nonproprietary or proprietary additives that improve the throwing pow- er and ductility of deposit is recommended for printed circuit application. A typ- ical formulation is shown in Table VII. Copper pyrophosphate baths are sensitive to contamination, especially organic con- Table VII. Copper Pyrophosphate for Printed Circuits Copper pyrophosphate (Cu2 P2 Potassium pyrophosphate (K4 Potassium nitrate O7 P2 O7 ·3H2 ) Concentrated ammonium hydroxide Addition agent pH Temperature Current density Agitation P2 Operating parameters by analysis are: Copper metal Pyrophosphate /Cu ratio O7 O) 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° 2.5-6.0 A/dm2 F) (25.0-60.0A/ft2 Mechanical and air 20.7-26.2 g/L (2.75-3.5 oz/gal) 150.0-204.4 g/L (20.0-27.2 oz/gal) 7.2:1-7.8:1 203 ) )

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