Electroplating Deposition rates

Electrodeposition of Metals. Citric acid and its salts are used as sequestrants to control deposition rates in both electroplating and electroless plating of metals (153—171). The addition of citric acid to an electroless nickel plating bath results in a smooth, hard, nonporous metal finish. 

Scenario In electroplating, the rate of deposition of metal is increased when the plating solution is warm. The shelf life of the solution, however, is reduced dramatically with the increased temperature. It is necessary to increase the rate of deposition with minimal degradation to the solution. How can this be done ... 

Plating rate as a function of pulse cycle is plotted in Fig. 5 for various pulse peak potentials. In the plating range, the pulse plating rate was not much different from that of DC plating. The potentials more positive to -0.8V vs SCE were not considered for electroplating as copper deposition rate was very low. 

Figures 5 and 6 show secondary electron SEM images of the electroplated deposits in cross section and plan view, respectively for samples plated in a solution containing 0.01M-0.02M ethylene diamine. The deposition rate increases between 1.2 and 3.2 mA/cm2. Note that the plating time at 1.2 mA/cm2 is 180 minutes, 90 minutes for the samples plated at 1.8 and 2.4 mA/cm2, and 40 minutes for the sample plated at 3.2 mA/cm2. The grain structure of the deposits also varies with an increase in current density. The sample plated at 1.2 mA/cm2 (Figures 5a, 6a) is gold rich and has a smooth surface containing fine pores about 0.1 pm in diameter, while the samples plated at 1.8 and 2.4 mA/cm2 (Figures 5a, 5b, 6a, 6b) exhibit a columnar structure which becomes more coarse with an increase in current density. The deposit formed at 3.2 mA/cm2 appears to have a mixed structure, the bottom two-thirds having a dense, feathery appearance, while the top third has a fine columnar structure.

This reaction mechanism which proceeds without any intermediate reactions involving other species generally favors a compact deposit and closely obeys Faraday s law, see Eq.(5.1), making a precise control over the deposition rate and thickness possible. Furthermore, the metal deposit is much more stable than the corresponding metal oxides that might be hydrated and readily redissolve. Since the metal electroplating is not considered to be a precipitation process, as in the case of various metal oxide depositions, the inclusion of impurities from the electrolyte are less likely. 

The catalyst system was obtained by the electroplating of a Co-Ni-P film on a Cu sheet. The film had amorphous morphology. NiSO concentration in the bath affected the deposition rate and catalytic activity of the catalyst system. The optimum value was 0.01 M for NiSO concentration. At this condition, hydrogen production rate was observed as 3636 mL min Bcataiyst 30°C. The activation energy was 38 kJ mol Hor sodium borohydride hydrolysis in the presence of Co-Ni-P catalyst film. Films had two distinct areas which were outer spherical particles and inner layer. These areas depended on NiSO, concentration. Increase in NiSO, concentration led to a decrease in the outer spherical catalyst particles and micro-cracks. It was concluded that catalysts production inner layer increased whereas catalyst production on the outer particles decreased. NiSO concentration increase led to an increase in Ni and P amount in the catalyst composition. However, Co amount decreased. At the optimum concentration that is 0.01 M NiSO, the composition was 80.5 at% Co, 5.0 at% Ni and 14.5 at% P. Above this point, the deposition rate increased but catalytic activity decreased [58]. Therefore, it was demonstrated that better compositional configurations should be investigated. 

Electrodeposition of conductive materials into PAA templates to form nanowire structures is readily xmdertaken under potentiostatic conditions, where the deposition rate remains constant and the deposited nanowires grow linearly with time. Based on the total measured amount of charge transferred and the approximate total volume of the nanowires, the electroplating process is 100% efficient when compared to the theoretical values. By measuring the charge transferred over a specific deposition time, the theoretical volume of material reduced in a 100% efficient process can be calculated. Thus, the height of the nanowires can be controlled and adjusted precisely. Figure 27 shows nickel metal nanowires electrodeposited in a PAA template. 

Electroless nickel coating is used because of its wear and corrosion resistance. Deposition rates (10 pm/h, or 0.4 mil/h) are relatively slow compared to electrode-position methods, but the electroless depositions are more uniform than those of electroplating. Normal thickness is... 

The Electrochemical impedance spectroscopy (EIS) results for the Mg alloy without and with surface Al coated from the 53 m/o and the 60 m/o ionic liquid, respectively, are depicted in Fig. 14.10. For bare Mg alloy, the polarization resistance was about 470 Qcm. A substantial increase in the polarization resistance, as evidenced by an enlarged diameter of the semicircle of the Nyquist plot, can be obtained for Mg alloy if it is electroplated with Al. For those with surface Al electrodeposited at -0.2 V from the 53 m/o and the 60 m/o ionic liquid, the polarization resistance in 3.5 wt% NaCl solution are 3000 and 5200 Qcm, respectively. The results were consistent with those revealed in the polarization curves demonstrated in Fig. 14.8. The improved polarization resistance of AZ91D Mg alloy with Al coating from ionic liquid is clearly demonstrated. However, the passivity or the polarization resistance of the Al-coated Mg alloy depends on the deposition conditions. The Al film formed in more acidic AICI3-EMIC and at a lower deposition rate renders a better passivation behavior. 

Fused-salt electroplating, which is commonly referred to as metal-liding, is a process for surface modification and surface hardening by electrodeposition fiom fused-salt electrolytes. Two unique aspects of this electrodeposition process are (1) elements that cannot be plated by conventional processes may plate by fused-salt electrodeposition and (2) if the deposition rate is controlled to match the diffusion rate of the... 

---