Combinatorial performance characteristics of agitated nickel hypophosphite electroless plating baths

In this article, we present the combinatorial performance characteristics of agitated sodium hypophosphite electroless plating baths. Various performance characteristics assessed include bath conversion, plating efficiency, selective conversion, metal film thickness, average pore size, effective porosity and percent pore densification (PPD). Bath agitation was brought forward by rotating a symmetric disk shaped porous ceramic substrate with a nominal pore size of 275 nm. The plating characteristics were investigated for wide range of nickel solution concentrations (0.04-0.16 mol/L), stirrer speed (0-200 rpm) and for two different loading ratios (defined as substrate surface area per unit volume of plating solution) values (196 and 393 cm²/L). It was evaluated that stirring had a profound effect on sodium hypophosphite based electroless nickel baths, which are characterized with lower conversions (10-39%) and higher plating efficiencies (62-99%) without stirring phenomena. The stirred plating baths provided about 20-56% excess nickel plating rate when compared to the baths without stirring. This lead to a reduction in average membrane pore size by 20-42 nm and an enhancement in percent pore densification values by about 2-7%. Further, higher concentrations as high as 0.16 mol/L have been found to be detrimental to reduce the metal plating efficiency to lower values (42%). Observed data trends confirm upon the urgent need to identify suitable mass transfer enhancement techniques that target enhancement in selective conversion while providing good values of plating efficiency and PPD.     

化学镀镍作为钢酸性镀铜前处理工艺的应用研究

为了防止钢表面酸性电镀铜出现置换铜,采取在电镀铜前增加化学镀镍工序,研究了化学镀镍工艺对酸性电镀铜的影响。结果表明,化学镀镍时间超过6 min时(镍层厚度>2.5～3μm),工件在酸性镀铜液中浸泡10 min,无置换铜出现。化学镀镍层对后续的酸性镀铜层的表面形貌和附着力均无明显影响,表明化学镀镍可作为钢酸性镀铜的底层。     

Nickel electroplating from glycine containing baths with different pH

Peculiarities of nickel electroplating from glycine-containing baths with different pH are considered as a function of the following factors: amino acid concentration, temperature, potential scan rate, and rotation rate of a disk electrode. Based on these data, a possible mechanism is proposed. It assumes that all the complexes present in the bath are reduced simultaneously so that the recorded cathodic current is determined by each current contribution. In the process, the reduction of Ni(II) glycinate complexes proceeds irreversibly and is controlled by the charge-transfer stage. The process involves an adsorption stage and a stage of a preliminary chemical reaction. The latter may represent the dissociation of nickel complexes or their mutual transformations caused by pH variations in the near-electrode solution layer. Original Russian Text ? N.V. Sotskaya, O.V. Dolgikh, 2008, published in Fizikokhimiya Poverkhnosti i Zashchita Materialov, 2008, Vol. 44, No. 5, pp. 514–521.     

Regeneration and decontamination of a nickel citrate complex in spent electroless nickel plating solutions

The possibility of citrate precipitation by excess metal ions in alkaline solutions suggests the use of Ni(II) together with OH^? to precipitate a Ni(II)-citrate complex from spent electroless plating solutions. After treatment of the precipitate with acid, excess Ni(II) can be removed in the form of insoluble Ni(OH)₂. The solution of the Ni(II)-citrate complex can then be reused for electroless nickel plating. During this procedure the additive adipate is not regenerated. For decontamination of spent electroless nickel plating solutions Fe(III) can be used as Ni(II)-citrate complex precipitant.     

新型高速氨性镀镍液性能的研究

研究了高速氨性镀镍液的性能。首先通过分析电流效率随电流密度的变化情况确定了镀液的许用电流密度,然后测定了氨的含量、镀液pH值、甲酸钠的含量等因素对分散能力、深镀能力、抗杂性能等镀液性能的影响。试验结果表明,研究的镀镍液体系许用电流密度达8．0A／dm^2,电镀速度比瓦特型镀镍液配方提高4倍左右,分散能力提高了16％,镀液的深镀能力也显著提高,而且镀液具有良好的抗铜离子的能力,抗铁离子的能力不太显著。     

The electrochemical recovery of nickel from plating residues

In view of the increasing demand for nickel and its compounds, the recovery of nickel values from any secondary source is of great importance, particularly in countries such as India where there is no domestic source of the metal. The buildups (or nodules) that accumulate during the nickel plating processes are one secondary source of metal. To take advantage of this resource, an electrochemical approach has been attempted to recover the nickel from plating wastes in the form of nickel sulfate. The approach involves selective anodic dissolution of the nickel nodules in a sulfuric acid medium and crystallization of the resultant nickel sulfate. Acidity, nickel concentration in the electrolyte and the extent of dissolution of the nodules have been examined with the intent of avoiding the loss of nickel at the cathode and reducing copper contamination in the electrolyte.