Silver electroplating additives

Silver-Lume A, B [ATOTECH]. TMfor a bright silver electroplating process for use by silversmiths and electronics manufacturers. The materials used are silver cyanide, potassium cyanide, potassium carbonate, and addition agents. 

The first commercial boards usiag electroless plating for connection between the sides were made by Motorola ia 1953 (41). An unclad plastic board was coated with electroless silver, a reverse resist appHed, and copper electroplated to the required circuit thickness. The resist and excess silver were removed. This semi-additive process is stiU used, with copper replacing the silver. 

In addition to the metals Hsted above, many alloys ate commercially electroplated brass, bronze, many gold alloys, lead—tin, nickel—iron, nickel—cobalt, nickel—phosphoms, tin—nickel, tin—zinc, ziac-nickel, ziac-cobalt, and ziac-iron. Electroplated alloys ia lesser use iaclude lead—iadium, nickel—manganese, nickel-tuagstea, palladium alloys, silver alloys, and zinc—manganese. Whereas tertiary and many other alloys can feasibly be electroplated, these have not found commercial appHcations. 

An interesting example of judicious choice of braze filler is to be found in the selection of silver alloys for the brazing of stainless steels to be subsequently used in a tap-water environment . Although the brazed joint may appear to be quite satisfactory, after a relatively short exposure period failure of the joint occurs by a mechanism which appears to be due to the break-down of the bond between the filler and the base metal. Dezincifica-tion is a prominent feature of the phenomenon and zinc-free braze alloys based on the Ag-Cu system with the addition of nickel and tin have been found to inhibit this form of attack. A similar result is obtained by electroplating 0-007 mm of nickel over the joint area prior to brazing with a more conventional Ag-Cu-Zn-Cd alloy. 

The alloy of zinc with copper is termed brass, pinchbeck, Muntz metal, and tombac. English brass usually contains 70 per cent, of copper and 30 of zinc. It is made by melting the copper and adding the molten zinc. The addition of nickel (Cu 52 per cent., Zn 23 per cent., Ni 13 per cent.) yields German silver, of which spoons, forks, and coins are made. Electroplate has usually a basis of this alloy, and is covered with silver by depositing it from its double cyanide with potassium. Zinc coated over... 

Silver selenite was prepared by addition of a selenious acid solution to a solution of silver nitrate. The product was recrystallised three times from nitric acid ( ). Sodium hydrogen selenite solution was prepared by neutralisation of recrystallised selenious acid by carbonate-free sodium hydroxide. The silver-silver selenite electrodes were obtained by first electroplating silver onto a platinum foil and then converting some of the silver to silver selenite by further anodic electrolysis. The procedure was apparently the same as used for the preparation of silver-silver chloride electrodes. The experiments were carried out in the dark or in subdued daylight. 

---