A customer inquired that during the production process of using acidic tin plating brighteners, the color of the tin coating on the workpiece is uniform, but the brightness is relatively poor. What is the reason for this?
Based on on-site experience and the characteristics of the product sulfuric acid based tin plating brightener Sn-807, Bigley Technology has analyzed the following 8 points:
1. The content of Tin(II) sulfate in the bath is too high. Tin(II) sulfate is the main salt of acid tin plating, which can improve the current density of cathode and accelerate the deposition rate. However, if the concentration of Tin(II) sulfate in the bath is too high, the dispersion ability of the bath will decline, the bright area will shrink, the color of the coating will become dark, and the crystallization will be rough. At this time, the plating solution should be diluted in time, and the concentration of Tin(II) sulfate should be adjusted within the process range.
2. The electroplating time is too short. The brightness of the coating is related to the thickness of the coating. When the plating time is too short, the coating is too thin and the brightness is poor. In this case, the electroplating time should be appropriately extended to ensure the thickness and brightness of the coating.
3. The temperature of the coating is too high. When the temperature of the general plating solution is too high, it will accelerate the hydrolysis of Sn2+. The plating solution is turbid, the coating is relatively rough, the consumption of brightener increases, the bright area of the coating narrows, and the weldability decreases. The impurity situation should be promptly reduced to the normal temperature range of the plating solution.
4. The current density is too high or too low. When the current density is too high, the coating is relatively loose, rough, and the edges are easy to burn, resulting in high brittleness; When the current density is too low, the deposition speed is too slow, and the brightness of the coating is poor. Therefore, we should set a reasonable current density based on the plating area of the workpiece during production.
5. Insufficient brightener content. Acid tin plating brightener can improve the polarization effect of the cathode, making the coating fine and bright. When the brightener content is insufficient, the workpiece cannot obtain a bright tin coating. Therefore, we should adopt the principle of adding less and frequently during the production process, and use the Hull cell experiment to adjust the concentration of the brightener.
6. Excessive metal or organic impurities in the plating solution. When the content of harmful metals such as Cu2+, Fe2+, and As3+in acidic tin plating solution is too high, the plating solution is relatively turbid, and the coating is prone to darkening and rough crystallization. When the content of organic impurities is high, the plating solution becomes turbid, the viscosity increases, and it is difficult to filter. The crystallization of the coating is rough, brittle, and prone to pinholes and pitting, and the brightness range is reduced. Therefore, we should regularly purify the plating solution during the production process.
7. The quality of the brightener is poor. Some brighteners have a lot of decomposition products during the production process, and there are many organic impurities in the plating solution used for long-term production. The workpiece coating is prone to faults such as pinholes and pits, and the brightness is poor. In addition, the consumption of brighteners is large, and the production cost is high. It is recommended to replace the brightener as soon as possible in this situation.
8. The water quality used in production is poor. The acid tin plating process has high requirements for water quality. When the water quality of the tank or added water is poor, the brightness of the coating is poor or completely lacking. Bigley suggests using pure water for tank preparation or replenishment.
So, in the production process of using acid tin plating brighteners, if the color of the workpiece coating is uniform but the brightness is relatively poor, we should conduct troubleshooting and adjustment according to the above 8 points to solve the problem as soon as possible and reduce losses. If you are interested in sulfuric acid hydrochloric acid based tin plating brighteners, you can contact Bigley customer service to obtain free samples and detailed technical information!
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