How to maintain acidic bright copper plating bath?

Acid bright copper plating solution should pay attention to the following three points in the maintenance: .

1) Strictly controlling process specifications is an important means to maintain the electroplating solution. Although the content of copper sulfate in the plating solution can vary within a relatively wide range, too large a difference in the content will also affect the performance of the plating solution. When the content of copper sulfate is too low, the brightness of the coating will decrease; when the content is too high, the copper salt is likely to crystallize out on the anode surface, causing anode passivation. In addition, the anode current density should be adjusted in time according to the temperature change of the plating solution and the intensity of stirring during operation. Under higher bath temperature and strong stirring conditions, a higher current density can be used; on the contrary, the current density should be lower, otherwise, the coating will be rough.

2) The correct use of additives is an important factor to ensure process stability. Practice has proved that the consumption of additives is related to many factors, such as temperature, current density, anode state, the amount of electricity passed and the content of sulfuric acid in the plating solution. Among them, the greater influence is the temperature of the plating solution and the amount of electricity passed. The consumption of additives is directly proportional to the amount of electricity passing through the electroplating tank. If the current is large and the time is long, the consumption of additives will be large; on the contrary, the consumption of additives will be small. The higher the temperature, the faster the consumption of additives; the lower the temperature, the slower the consumption of additives. Under normal operating conditions, about 1mL of additives need to be added after each liter of solution is energized for 4A·h. Since the electrode behavior of each component in the additive is different, the relatively stable content cannot be maintained by a uniform additive. The empirical method must be used to judge the consumption of the additive. In the production process, due to the small content of each component of the additive, the content of the additive in the plating solution cannot be known by general analysis methods. The simplest feasible method is to judge by observing the brightness of the coating while changing the moving speed of the cathode. When the speed of cathode movement is increased, if the obtained coating is brighter than before, it indicates that the brightener is insufficient and needs to be added; when the cathode movement speed is slowed down or the movement is stopped, if the obtained coating appears brighter instead , It shows that the additive has been excessive.

3) Harmful impurities should be prevented from entering the plating tank. Anions such as nitrate, chloride and chromate will have an adverse effect on the performance of the bath. The acidic bright copper plating solution is more sensitive to chloride ions. When there is a lack of chloride ions, it is difficult to obtain a bright coating with good leveling even if the additive content is within the normal range. When the chloride ion mass concentration is 20-40mg/L, the gloss of the coating is the most ideal, and the brightness of the coating will decrease if it exceeds 80mg/L. Therefore, the chloride ion content in tap water should be known in advance when preparing the plating solution. If it exceeds the process specification, it should be prepared with distilled water or deionized water, and then supplemented with an appropriate amount of chloride ion. In order to avoid the introduction of chloride ions as much as possible, it is best not to use hydrochloric acid when the workpieces (especially complex workpieces) are activated before plating, but to use sulfuric acid instead. The introduction of nitrate will make the dispersion ability of the plating solution worse, and the introduction of chromate will cause the coating to be weakly bonded and peeling. Therefore, special attention should be paid to prevent accidental addition.