COMBINED ADDITIVE TO FLUORIDE ELECTROLYTES FOR THE DEPOSITION OF TIN-COBALT COATINGS

摘要

The combined additive is designed for the production both of low- (to 0.1%), and to medium- and high-alloyed (over 5-6%) tin-cobalt coatings. It finds application in the manufacture of printed circuits û the coating being used as metal resist, for the substitution of silver in microelectronics and the electrical industry, as well as in different fields of mechanical engineering, instrumentation and others, with the intention of substituting the decorative chromium depositions. The combined additive contains polyethyleneglycol 400 (PEG 400) 0.5- 2 ml/l, cyclohexanol 0.05 û 0.2 ml/l and potassium rhodanide from 20 to 40 g/l, and for the low-alloyed coatings a mixture of PEG 400 and cyclohexanol is used, and to the medium- and high-alloyed substances potassium rhodanide with the said concentrations is also added. The additive is equally effective and by it high-quality depositions are produced both from the fluoride-sulphate, and of the fluoride-chloride electrolytes at room temperature.In its presence, the low-alloyed depositions are of fine crystals, non-porous, and having high resistance in alkaline etching solutions and in other media having an inclination to bonding and having low contact resistance. The high-alloyed depositions are lucent, resembling to that of the lucent chromium, have higher micro-hardness and wear resistance in comparison with the low-alloyed ones, and simultaneously their internal stress is much lower than that of the lucent chromium depositions and are highly adaptable to passivation.