Reduction of palladium (II) complexes with sodium tetrahydroborate for electroless metallising of plastics

In this approach to electroless copper plating of plastics, the activation of the polymer is followed by immersion in alkaline palladium sulphate solution. In addition to the subsequent desired reaction, that is formation of metallic copper on the surface after reduction by the tetrahydroborate, an undesired reaction is the homogeneous analogue in solution. This can be repressed using a solution with 2 to 3 gm/l NaBH4 and 60 to 80 gm/l NaOH. Similar effects can be obtained by addition of 5 to 6 gm/l boric acid and 2 to 3 gm/1 NaF. Bath stability can be further increased by addition of stabilisers such as sodium diethyldithiocarbamate and thallium nitrate which have a further beneficial action by increasing the copper deposition rate.