Electrodeposition of platinum from a cis-diamminedihaloplatinum (II) electrolyte

#The present invention is directed to a bath and process for the electrodeposition of platinum utilizing a complex platinum compound as the effective ingredient in the bath.

#As is known, electrodeposits of platinum have considerable utility in the industrial world. In particular, electrodeposited platinum is useful as an electrode material per se and especially when deposited on metals such as titanium and tantalum. In addition, platinum is known as an effective barrier in high temperature electronic applications. Plating baths based upon the water-soluble salt, platinum diammine dinitrite, have been used for approximately fifty years. The invention is directed to the provision of a new platinum electroplating bath and process for producing electrodeposits of platinum.

#The invention is directed to aqueous plating baths containing as effective ingredients cis diammine dichloroplatinum (II) and dimethylformamide, and to the electrodeposition of platinum therefrom.

#In accordance with the invention an electroplating bath is provided containing about 8 grams to about 10 grams per liter of platinum added to the bath as a complex salt from the group consisting of cis diammine dichloroplatinum (II) and cis diammine diiodo platinum (II), a halide salt from the group consisting of sodium chloride and sodium iodide in the amount of about 15 to about 25 grams per liter and a liquid phase comprising water and dimethylformamide in volume ratios of about 1:1 to about 1:2. Preferably, sodium iodide is employed with the diido platinum salt, and sodium chloride is employed with the dichloro platinum salt.

#The bath can be employed to produce sound adherent platinum electrodeposits at a cathode immersed therein employing a cathode current density of about 0.5 to about 2 amperes per square decimeter, a bath temperature in the range of about 45.degree. C. to about 70.degree. C., and a bath pH from about 6.0 to about 9.0. Cathode current efficiencies up to about 50% can be obtained.

#Those skilled in the art will appreciate that the function of the dimethylformamide in the bath is to act as solvent for the water-insoluble platinum salt, while the halide salt contributes to conductivity of the bath.