Plated copper plating considerations

Constructional details of a modem lead-acid cell for locomotives in coal mines are given in Fig. 6.67. A copper expanded metal lattice parallel with the negative plate considerably lowers the internal resistance of the cell. The total view of a 540V 80 Ah lead-acid accumulator for locomotives in coal mines is given in Fig. 6.68. 

However, when the amount of added particles increased(W=2.0 or 3.0wt.%), the effective surface area of cathode plate decreased due to the considerable increase of solid holdup between the two electrodes, thus, the amount of copper recovery decreased. In this experimental conditions, the distance between the two electrodes(LAc) also influenced the recovery of copper, as can be seen in Fig. 7. In this figure, the value of R was maximum when the distance(LAc) was 1.5cm, in all the cases studied. 

The concentrates of salt solutions made by electrodialysis of seawater are suited as feed to the evaporators of salt manufacturing plants with considerable savings in overall energy requirements. Other applications also are based on the concentrating effects of electrodialysis, for instance, tenfold increases of concentrations of depleted streams from nickel and copper plating plants are made routinely. 

Anodes. There are two types of anodes soluble and insoluble. Most electroplating baths use one or the other specifically however, a few baths use either or both. Chromic acid plating baths use insoluble anodes alkaline zinc cyanide baths use both noncyanide alkaline zincs may use either. Soluble anodes are designed to dissolve efficiendy with current flow and preferably, not to dissolve when the system is idle. A plating solution having the anode efficiency close to the cathode efficiency provides a balanced process that has fewer control problems and is less cosdy. If the anode efficiency is much greater than the cathode efficiency and there are only small solution losses, the dissolved metal concentration rises until at some time the bath has to be diluted back or the excess metal has to be reduced by some other means. If the anode efficiency is less than the cathode efficiency, the dissolved metal decreases, pH decreases, and eventually metal salt additions and other solution corrections are required. Based on the cost of metal, it is usually considerably more economical to plate from the anode rather than add metal salt. Copper cyanide, for example, costs about twice as much to add than to dissolve a comparable amount of copper anode. Additionally, the anion added with the metal salt may build up in the plating solution. 

Other factors, of course, come into play in an actual plating bath. For example, plating from an acid bath takes place at around 0.3 V, NHE, whereas in a cyanide bath, copper is deposited at a much more negative potential. The former occurs at a positive rational potential, while the latter occurs at a negative rational potential. This affects the choice of additives and their adsorption characteristics. Also, the values of ( ) and d( ) /d( ) may be different in the two cases. The foregoing example is not intended to be a quantitative interpretation of the benefits of cyanide baths, but rather an illustration of how considerations of a rather fundamental nature can assist in solving applied problems. 

Owing to the increasing technological interest of the electronics industry in electroless copper plating, a considerable amount of R D is still in progress in this field, and many publications continue to appear in the literature. It is impossible to review... 

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