STABILIZERS OF SOLUTIONS OF CHEMICAL COPPER PLATING

The work is devoted to the study of the effect of various compounds on the stability of elec-troless copper plating solution containing Trilon B. as a chelating agent. The stability of electroless copper plating solutions was estimated by the accelerated method as the time before the start of intensive decomposition of the solution after the introduction of 0.15 ml of colloidal palladium activator solution heated to 75 degrees C in 250 ml. As stabilizers, both known, currently used, and newly selected compounds were investigated. Sulfur-and/or nitrogen-containing organic and inorganic compounds such as: sodium diethyldithiocarbamate, 2,2'-dipyridyl, thiosemicarbazide, potassium hexacyanoferrate (III), potassium hexacyanoferrate (II), thiourea, thioglycolic acid, dimethylgly-oxime, potassium rhodanide in concentrations in the range of 1 -50 mu mol/l were among the first studied. It is shown that when the stabilizers are contained in the solution at the optimal concen-trations set (for each compound), solutions containing sodium diethyldithiocarbamate, thioglycolic acid, thiosemicarbazide, thiourea (in descending order of stabilizing action), i.e. compounds con-taining a sulfur-carbon bond, have the greatest stability. With this in mind, other sulfur-containing compounds, including heterocyclic ones, were selected and studied as stabilizers: alpha-lipoic acid, thi-amine chloride, methyl orange, nitroso-p-salt, methylene blue and SPADNS (sodium salt of 2- (psulfophenylazo)-1,8- dihydroxynaphthalene-3,6-disulfonic acids). In addition, nitrogen -contain-ing compounds that were not previously used in electroless copper plating solutions as stabilizers were also studied: nicotine, pyridoxine, Janus Green B (8-(4-dimethylaminophenyl) diazenyl-N, N-diethyl-10-phenylphenazine-10-ium-2-amine chloride), nigrosine, however. Solutions of electro-less copper plating in the presence of these compounds did not show high stability. It has been established that the most effective, comparable in effect to the stabilizers currently used, are alpha-lipoic acid and thiamine chloride. The advantages of the latter are their availability and low toxicity.