Too high a current density will lead to coarse coating crystals, porosity increase, reduce the densification, need to reduce the current density or adjust the composition of the plating solution (such as adding surfactants) to improve the densification, but it will prolong the plating time, reduce production efficiency.
Author: Anna
I. Trade-off between current density and deposition rate
The effect of high current density on densification
Too high a current density will lead to coarse coating crystals, porosity increase, reduce the densification, need to reduce the current density or adjust the composition of the plating solution (such as adding surfactants) to improve the densification, but it will prolong the plating time, reduce production efficiency.
Although the current density is too low to improve the densification, but the deposition rate drops significantly, affecting the overall efficiency.
Current Efficiency Constraints
When plating densities are increased, current efficiency may be reduced due to increased polarisation effects. For example, too high a concentration of trivalent chromium in the chromium plating solution will narrow the range of bright current density, resulting in a decrease in current efficiency.
II. Indirect effect of plating solution parameter adjustment on efficiency
Liquid composition control
In order to improve the densification needs to maintain the stability of the ionic concentration of the plating solution (such as the balance of copper sulfate and sulfuric acid), frequent adjustments will increase the complexity of the process, reducing the continuity of operations.
Addition of brighteners (e.g. DE series) can refine the grain size, but excessive additives may inhibit the deposition rate and prolong the plating cycle.
Temperature and pH Control
Higher temperatures reduce differential polarisation and speed up deposition, but too high temperatures (e.g. zincate galvanising over 40°C) can lead to a loose layer structure and require additional cooling steps.
pH value deviation from the optimal range (e.g. chemical nickel plating pH>5.2) will reduce the densification of the layer, need to be adjusted frequently, increasing energy consumption and time costs.
III. Process Time and Energy Costs
Extended plating time
It takes longer time to deposit dense plating layer under low current density, equipment occupancy rate increases, and output per unit time decreases.
Increased energy consumption
Additional energy consumption (e.g. heating, filtration equipment) is required to maintain bath temperature, stirring speed and other parameters to optimise densification.
IV. Post-treatment and rework rates
Defect Repair Costs
In case of insufficient densification (e.g. pinholes or cracks), de-plating and reworking are required, which directly reduces the overall efficiency.
Passivation and sealing process
In order to make up for the densification defects, additional passivation treatment (such as chromate passivation) is required, increasing process time and chemical consumption.
There is a dynamic equilibrium between plating densities and plating efficiency:
Positive impact: High densities reduce rework, extend plating life and indirectly increase long-term efficiency.
Negative: Optimising densities sacrifices deposition speed, increases process complexity and energy consumption, and reduces efficiency in the short term.
In practice, a compromise between process parameters should be chosen based on the requirements (e.g., precision electronic parts prioritise densification, general parts focus on efficiency).