Development of the Process for Electroplating with Thick Palladium for the Purpose of Suppression of Metallic Allergy

A new electrolyte(Plating Bath)has been developed for palladium electroplating，NH I D24 I D 2H I D 22 I D 2 PO I D 24 I D 2(100 kg/m I D 13 I D 1，NH I D 24 I D 2 Cl(25 kg/m I D 13 I D 1)，and pure water(900毫升)have been added in the NH I D 24 I D 2 OH solution(100毫升)constrained PdCl I D 22 I D 2(17 G).Palladium was electroplated copper substrates at current densities of 20-200A/m I D 12 I D 1.The current efficiency for palladium deposition was about95%at20-30A/m I D12 I D 1.The plating film at this condition was excellent in luster.The concentration of hydrogen in the palladium electroplated copper specimens was measured by using the heat extraction method，and the palladium plating films were found to contain a large amount of hydrogen.From this result，the inability to obtain thick palladium films is estimated to be the pickup of hydrogen during a plating process，and the deterioration in mechanical properties of the plating film by the hydrogen embrittlement.Then，a relation between the plating condition and the hydrogen concentration was examined.The hydrogen concentration in the plating film did not depend on film thickness.And the concentration was 120 mass-ppm at 20A/m I D 12 I D 1 and 20-30 mass-ppm at current densities larger than 20A/m I D 12 ii D 1.In order to reduce the hydrogen concentration in the plating film，the diffusion coefficient of hydrogen，D I D 2 H D 2 in palladium electroplating films were measured by the electrochemical desorption method.The following has been understood as a result。(1)D I D 2 H D 2 in the palladium plating film was smaller than D D 2 H D 2 in palladium bulk.(2)D I D 2 H D 2 became large by heat-treating，and D I D 2 H D 2 in the plating films heat-treated at high temperatures was identical with D I D 2 H D 2 in the bulk.(3)The main cause，that D I D 2 H I D 2 in the plating films was smaller than that in the bulk，was clarified to be a residual strain in the plating film.

A new electrolyte (plating bath) has been developed for palladium electroplating, NHィイD24ィエD2HィイD22ィエD2POィイD24ィエD2 (100kg/mィイD13ィエD1, NHィイD24ィエD2Cl (25kg/mィイD13ィエD1), and pure water (900ml) have been added in the NHィイD24ィエD2OH solution (100ml) constrained PdClィイD22ィエD2 (17g). Palladium was electroplated copper substrates at current densities of 20-200A/mィイD12ィエD1. The current efficiency for palladium deposition was about 95% at 20-30A/mィイD12ィエD1. The plating film at this condition was excellent in luster. The concentration of hydrogen in the palladium electroplated copper specimens was measured by using the heat extraction method, and the palladium plating films were found to contain a large amount of hydrogen. From this result, the inability to obtain thick palladium films is estimated to be the pickup of hydrogen during a plating process, and the deterioration in mechanical properties of the plating film by the hydrogen embrittlement. Then, a relation between the plating condition and the hydrogen concentration was examined. The hydrogen concentration in the plating film did not depend on film thickness. And the concentration was 120mass-ppm at 20A/mィイD12ィエD1 and 20-30mass-ppm at current densities larger than 20A/mィイD12ィエD1.In order to reduce the hydrogen concentration in the plating film, the diffusion coefficient of hydrogen, DィイD2HィエD2 in palladium electroplating films were measured by the electrochemical desorption method. The following has been understood as a result. (1) DィイD2HィエD2 in the palladium plating film was smaller than DィイD2HィエD2 in palladium bulk. (2) DィイD2HィエD2 became large by heat-treating, and DィイD2HィエD2 in the plating films heat-treated at high temperatures was identical with DィイD2HィエD2 in the bulk. (3) The main cause, that DィイD2HィエD2 in the plating films was smaller than that in the bulk, was clarified to be a residual strain in the plating film.