In acid bright copper plating process, due to the small content of each component of the additive, the level of the additive in the plating solution cannot be known by the general analysis method.
The acid bright copper plating solution should pay attention to the following three points in maintenance:
1. Strict control of process specifications is an important means of maintaining plating solutions. Although the content of copper sulfate in the plating solution can be varied within a relatively wide range, the difference in content is too large and will 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 will easily form crystals on the surface of the anode, resulting in anode passivation. In addition, the anode current density should be adjusted in time according to the change of the bath temperature and the intensity of the stirring. At higher bath temperatures and strong agitation conditions, larger current densities can be used; conversely, the current density should be smaller, otherwise the coating will be rough.
2. Proper use of additives is an important factor in ensuring process stability.
There's proof shown 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 most influential is the temperature of the plating solution and the amount of electricity passed. The amount of additive consumed is positively proportional to the amount of electricity that passes through the plating bath. when the current is big, the time is long, and the additive consumption is large; on the contrary, the additive consumption is small. When the temperature is high, the additive consumption is fast; when it is low, the additive consumption is slower. Under normal conditions, about 1 mL of additive is required after each liter of solution is energized for 4 A•h. Since the electrode behavior of each component in the additive is different, the relatively stable content cannot be maintained with a uniform additive, and the consumption of the additive is judged by an empirical method. In the production process, due to the small content of each component of the additive, the level of the additive in the plating solution cannot be known by the general analysis method. The simplest and most feasible method is to judge the brightness of the coating by changing the moving speed of the cathode. When the speed of the cathode movement is accelerated, if the obtained coating is brighter than before the acceleration, it indicates that the brightener is insufficient and needs to be added; when the cathode moving speed is slowed or the movement is stopped, if the obtained coating is more bright , indicating that the additive has been excessive.
3. Harmful impurities should be avoided from entering the plating tank.
Anions such as nitrate, chloride and chromate have an adverse effect on the performance of the bath. The acid bright copper plating solution is sensitive to chloride ions. When the chlorine ions are lacking, it is difficult to obtain a full-brightness coating with good leveling even if the additive content is within the normal range. When the mass concentration of chloride ion is 20-40 mg/L, the gloss of the coating is most ideal, but when it exceeds 80 mg/L, the brightness will decrease. Therefore, in the preparation of the plating solution, the chloride ion content in the tap water should be known in advance. If it exceeds the process specification, the distilled water or deionized water should be used for preparation, and then the appropriate amount of chloride ions should be added. In order to avoid the bring-in of chloride ions, it is best to use hydrochloric acid instead of hydrochloric acid in the pre-plating activation of the workpiece (especially complex workpieces). The presence of nitrate will make the dispersion of the plating solution worse. The introduction of the chromate will result in poor adhesion of the coating and peeling of the coating. Therefore, special attention should be paid to prevent accidental addition.
Above the three points, choosing quality plating additive in acid copper plating can reduce your maintenance cost. I.M.T.’s acid bright copper plating additives has won good reputation among customers with the following advantages:
Our bright acid copper plating process has excellent comprehensive performance, which shows outstanding brightening and leveling effect.
It provides workpiece with good flexibility and corrosion resistance.
This acid copper plating bath is stable and easy to control with wide operation range.
With low consumption, it has high performance-cost ratio which can improve competitiveness of products.