Reasons for the formation of bubbles in the electroplating tank The electroplating tank also has internal or external reasons for the generation of bubbles. Today, this article will introduce to you from both internal and external aspects the reasons for the bubbles generated in the electroplating tank. Those who are interested in children’s shoes can take a look with this editor!
A. The internal cause of bubbles
Fortunately, the acid copper plating bath has a very high cell efficiency, so hydrogen generation in a better bath is a small problem. What needs to be avoided is the conditions that are likely to cause hydrogen generation, such as high current density and rectifier fluctuations that cause short-term large current density drift. Some tin/lead baths or tin baths are less efficient than copper baths. Hydrogen generation becomes an important issue. An interesting development in avoiding the generation of hydrogen fractionation is the addition of “antipititting additives”. These organic compounds, such as caprolactam derivatives, may participate in redox reactions, taking away atoms before forming hydrogen molecules. The state of hydrogen prevents the generation of bubbles. The reduced “anti-pit additive” is re-oxidized at the anode and transferred to the cathode to restart the cycle.
B. External causes of bubbles
The most obvious external cause of bubbles is the bubbles filled in the holes before the board is immersed in the solution. In order to drive the air out of the holes before the board is immersed in the bath, some electroplating fixture designers have experimented with forming a certain angle between the board and the fixture. Paddle agitation can generate enough pressure differential to drive air bubbles out of the holes. Using compressed air through a sprayer to agitate the liquid (air sparging) through the surface of the plate also helps to drive away air bubbles. Of course, the spray stirring itself is also a kind of gas, mixed into the tank, the air enters the circulating filter pump to produce a supersaturated liquid flow, which will form bubbles at the gathering position, and also form bubbles at the defects of the hole wall. Some manufacturers are troubled by this problem and turn to airless agitation (solution spraying).
In addition to resist residues and bubbles that hinder electroplating, other obvious problems that cause electroplating voids are: poor penetration and foreign body blockage. Poor penetration of the bath will cause no copper in the middle, but this is a very extreme situation. Usually, the copper thickness in the center of the hole is not enough to meet the acceptance standard. In the acid copper plating bath, the poor penetration is caused by the following reasons: improper copper/acid ratio, bath contamination, less or insufficient organic additives, poor current distribution, blocking effect or stirring, etc. If particle contamination is found, it is mostly caused by a failure of the circulation or filter pump, the frequency of tank reversal is too low, the anode bag is damaged or the cathode membrane is defective.
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Link to this article：Causes of bubbles in the electroplating bath
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