What is a punctate hole break? How to avoid it?

The broken state is a phenomenon in which points are distributed instead of the whole circle of open circuit. It is called a point-shaped hole, and it is also called a 'wedge-shaped hole.' The common cause is the poor handling of the slag removal process. The circuit board dross removal process will first be treated with a leavening agent, and then a strong oxidizer 'permanganate' will be corroded. This process will remove the scum and produce a microporous structure. The oxidant remaining after the removal process is removed by a reducing agent, and the typical formula is treated with an acidic liquid. Because after the glue residue is processed, there will be no more glue residue problems, and the industry often neglects the monitoring of the reducing acid solution, which may allow the oxidant to remain on the wall of the hole. After the circuit board enters the chemical copper manufacturing process, the circuit board will undergo micro-etching treatment after the pore forming agent is treated. At this time, the residual oxidant is again soaked in acid to peel off the resin in the residual oxidant area, which is equivalent to destroying the pore forming agent. The damaged pore wall will not react in the subsequent palladium colloid and chemical copper treatment, and these areas will show no copper precipitation phenomenon. If the foundation is not established, of course, the electroplated copper will not be able to cover it completely and cause dot-shaped holes. This kind of problem has occurred in many circuit board factories. Paying more attention to the potion monitoring of the reduction step of the de-smear process should be able to improve, the above is for reference only.