The most critical factor in the maintenance of etching equipment is to ensure that the nozzle is clean and there is no obstruction to make the spray smooth. Blockages or slagging can impact the layout under the jet pressure. If the nozzle is not clean, it will cause uneven etching and the entire PCB will be scrapped.
Obviously, the maintenance of equipment is to replace damaged and worn parts, including the replacement of nozzles, which also have wear problems. In addition, the more critical issue is to keep the etching machine free of slagging, and slag accumulation will occur in many cases. Too much slag accumulation will even affect the chemical balance of the etching solution. Likewise, if the etchant exhibits an excessive chemical imbalance, slag formation will be exacerbated. The problem of slag buildup cannot be overemphasized. Once a large amount of slagging occurs suddenly in the etching solution, it is usually a signal that there is a problem with the balance of the solution. This should be properly cleaned with stronger hydrochloric acid or the solution should be replenished.
Residual film can also produce slag, and a very small amount of residual film dissolves in the etching solution, and then forms copper salt precipitation. The slag formed by the residual film indicates that the previous film removal process is not complete. Poor film removal is often the result of a combination of edge film and overplating.
A large number of problems related to etching quality are concentrated on the etched part of the upper board. It is important to know this. These problems arise from the effects of colloidal build-up from etchants on the upper surface of the printed circuit board. The colloidal solids accumulate on the copper surface, which affects the ejection force on the one hand, and blocks the replenishment of fresh etching solution on the other hand, resulting in a decrease in the etching rate. It is precise because of the formation and accumulation of colloidal solids that the etching degrees of the upper and lower patterns of the board are different. This also makes the part of the board that enters first in the etching machine easy to be completely etched or easy to cause over-corrosion, because the accumulation has not been formed at that time, and the etching speed is faster. Conversely, when the part entering the back of the board enters, the buildup is already formed and slows down its etch rate.
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