Electroplated Copper Electroplated Lead Tin (Into Pure Tin) Related Holes

Plating baths also have internal or external causes of air bubbles.

A. The inherent causes of air bubbles

Fortunately, the acidic copper plating bath has a very high cell efficiency, so in the case of a better tank hydrogen production is a minor problem. What needs to be avoided is the conditions that are likely to lead to the generation of hydrogen, such as: high current density and rectifier fluctuations cause short-duration large current density drift. Some tin/lead or tin baths have a lower efficiency than the copper bath. This is an important issue. An interesting development in avoiding hydrogen segregation is the addition of "antipititting additives". These organic compounds, such as caprolactam derivatives, may participate in redox reactions and take away atoms before forming hydrogen molecules. Hydrogen in the state prevents bubbles from forming. The reduced "crater additive" is reoxidized at the anode, transferred to the cathode, and the cycle is resumed.

B. The external causes of air bubbles

The most obvious external cause of bubbles is the filling of air bubbles in the holes before the board is immersed in the solution. In order to drive out the air in the hole before the board is immersed in the bath, some plating jig designers have experimented to make the board and the jig form an angle. Paddle agitation can generate enough pressure differential to drive air bubbles out of the hole. Air sparging through compressed air through the sprayer also helps to expel the air bubbles. Of course, spray agitation is also a kind of gas, and it is mixed into the tank. The air enters the circulating filter pump to produce a supersaturated liquid flow. Bubbles are formed at the gathering position and bubbles are formed at the defects of the hole wall. Some manufacturers have been troubled by this problem and have turned to airless stirring (solution spraying).

In addition to the obstacles such as resist residue and air bubbles that hinder electroplating, other obvious problems that cause electroplating voids are: penetrating power and poor and foreign matter clogging. Poor penetration of the bath results in no copper in the middle, but this is a very extreme situation. Usually the copper thickness in the center of the hole is insufficient and the acceptance standard cannot be achieved. In acidic copper plating baths, there are several reasons for the poor penetration: improper copper/acid ratio, contamination of bath solution, low or insufficient organic additives, poor current distribution, blocking effects, or agitation. If the particles are found to be contaminated, the circulation or the filter pump is mostly faulty, the frequency of the inverted trough is too low, the anode bag is broken or the cathode film defect is caused.