Implementation points: need to establish a whole-process traceability system from raw material incoming inspection to finished product packaging, focus on monitoring the plating solution composition decay curve (e.g., monthly consumption of nickel sulfate is about 8-12%34), and realize quality stability management through SPC statistical process control
Author: Anna
I. Precise control of plating solution composition
1. Main salt concentration control
Control the concentration of nickel sulfate at 150-200g/L (rack plating) or adjust the concentration of barrel plating appropriately to avoid too high a decrease in dispersion or too low a restriction on the deposition speed.
Nickel chloride (conductive salt) is kept at 40-60g/L to maintain solution conductivity and activate the anode.
2. Additives regulation
Adjust dynamically according to plating phenomena:
- When the edge is white/leakage plating, add gloss agent and adjust pH to 4.2-4.6;
- When fogging in the high current area, supplement the alignment agent or wetting agent.
3. Boric acid buffer
Ensure that the solubility of boric acid meets the standard, stabilize the pH value in the range of 3.5-4.6, and prevent the hydrogen precipitation reaction from destroying the plating layer.
II. Optimization of process parameters
1. Current density matching
Ordinary nickel plating adopts 2-4A/dm², high-speed plating can be upgraded to 5-10A/dm², which needs to be adjusted in combination with the temperature of plating solution and stirring speed.
2. Temperature and agitation synergy
Temperature control at 45-60℃ (Watts liquid), with air or mechanical agitation, to avoid scorching or coarse crystallization of the plating layer.
3. pH dynamic monitoring
Use pH meter to monitor in real time, and correct immediately when the deviation exceeds 0.2 to prevent the plating layer from increasing brittleness or decreasing bonding.
III. Enhancement of substrate surface treatment
1. Pre-treatment process
Add electrolytic polishing or chemical polishing after degreasing and degreasing to ensure that the surface roughness of the substrate Ra ≤ 0.8μm, to enhance the adhesion of the plating layer.
2. Activation process improvement
Adopt 10% sulfuric acid activation instead of hydrochloric acid system to reduce the corrosion risk of chlorine ion residue on the plating layer.
IV. Process quality control system
1. Key control point setting
Set up control points in etching, pre-plating, plating, hydrogen repellent, etc., and test the thickness, porosity and bonding strength of the plated layer every 2 hours.
2. Plating solution impurity removal
Regularly use activated carbon filtration (0.5g/L treatment) to adsorb organic impurities, and metal impurities are removed by low-current electrolysis.
V. Detection and Correction Mechanism
1. Quick problem diagnosis
For the phenomenon of blackening/yellowing of the plating layer, prioritize the investigation of abnormal pH value or additive imbalance instead of directly replacing the plating solution.
2. Plating performance testing
Adopt the grid method to test the bonding force, ammonium nitrate test to detect porosity, XRF spectroscopy to analyze the composition of nickel layer.
3. Closed-loop correction of process parameters
Establish the mapping relationship table between plating defects and process parameters (e.g. pinholes corresponding to temperature/stirring abnormality), and realize automatic compensation adjustment.
Implementation points: need to establish a whole-process traceability system from raw material incoming inspection to finished product packaging, focus on monitoring the plating solution composition decay curve (e.g., monthly consumption of nickel sulfate is about 8-12%34), and realize quality stability management through SPC statistical process control.