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Factors impact electroplating solution dispersion and coverage capability:
The advantages and disadvantages of plating solution indicated by dispersion and coverage capability. Dispersion capacity refers solution has capability of uniform distribution in coating thickness, which only shows uniformity coefficient on the surface of plating workpiece. Coverage refers the electroplating solution has capacity of depositing coating film on parts deep hole, concavity surface, also called depth capability. Only stated plating surface concavity surface or deep hole whether has coating deposition or not.
1, Current distribution: When the current through the electrolyte solution, the amount of material deposited on the cathode in direct proportion to the electric quanlity through. Greater current density, the coating film is also the more thicker. Metal deposition on the cathode surface depends on the distribution of electricity in cathode. The electrolyte solution resistance and cathode electrochemical reaction resistance, are two important factors which impact the current distribution in cathode, and one of them play a dominant role. 2, Current efficiency: coating film metal distribution depends on the current distribution, but it does not mean equal to current distribution. Through primary current not only consumed metal ion deposition, but also consumed in hydrogen and other side effects. Current efficiency changes with current density changing.
Affect the distribution of the metal in different parts : A. Cathode current efficiency with current density change almost no change . Different parts of the cathode plating metal depends directly on how much the size of the current. B. Cathode current efficiency with the increasing of current density but decrease to improve the dispersion capacity. Where the current density high the low current efficiency, while the low current density the high current efficiency. To make the current density distribution uniform, have to change the dispersion capability of the electrolyte solution. C. The surface state of organism:
Metal hardly deposited on the unclean cathode surface a uniform coating, or even can not deposite. Since hydrogn overpotential on rough surface less than on smooth surface, then on rough surface the hydrogen is easily to precipitate, so it is difficult to deposit coating film. D. Cathode current efficiency with the increasing to increase will reduce dispersion capacity. Because of the electrical efficiency is high when the cathode current density high, but the current density low when current low, so the actual current density throughout more uneven, resulting in poor dispersibility . E. Geometric factors:
Plating tank geometry shape, the shape of the anode and cathode, the two electrodes in the plating tank etc.. geometric arrangement factors can directly affect the distribution of coating .
Explain: All these related with the electrolyte solution dispersion and coverage capability, are not isolated from each other, but actual contacted each other.