“Cleaning” is a necessary process in almost every chemical process of PCBA manufacturing industry. PCBA cleaning is usually the key procedure by following the chemical process, but it is often regarded as a procedure that needs little attention. However, the problem caused by ineffective cleaning is result in defective products, it also brings huge operating costs for the waste disposal department.
Definition of circuit board cleaning
At first, cleaning is usually defined as the removal of process solution in process or on PCB panel. It’s not entirely accurate, but it’s a fact. Generally speaking, cleaning is not the complete removal of pollutants, but diluting the solution in the process or on the PCB panel to a controllable concentration. According to this definition, cleaning systems can be designed to minimize harmful contaminants on printed circuit boards while reducing water consumption.
It is often asked if there are standards that can be applied to the cleaning process. Are all kinds of pollutants the same? Is there a strict rule for cleaning? The shortest answer is, not quite correct. The composition of controllable concentration depends on the following three conditions:
2、 PCBA pollution status
To investigate the contamination, we added the same alkaline cleaner to the persulfate based micro etching solution and the acid copper plating solution and compared them. Both solutions are acidic, and part of the acidity will be neutralized by the added alkali residue. According to the concentration, the neutralization effect of alkaline solution on micro etching solution is almost ignored. This is because the acidity of the micro etching solution is generated by the spontaneous decomposition of persulfate, so the acidity can be reduced to a certain extent and can be spontaneously supplemented.
However, when investigating the acidic copper plating solution, we found that the solution is extremely sensitive to pollutants and may be destroyed by pollutants at the same level as the micro etching solution (which has no effect on the micro etching solution). It can be concluded that a certain level of pollutants in alkaline detergent can be tolerated by a certain production solution, but it may not be tolerated by a different production solution. Therefore, we need to determine the controllable pollution level for each specific process.
In both cases, effective cleaning will extend the service life of the production solution. An efficient cleaning system that can effectively remove enough process solution can reduce the cost of chemicals and waste rate, and reduce the burden of waste treatment system.
In some areas, although the cascade cleaning method will greatly increase the water consumption, it is still popular; In other areas, such as PCB manufacturers will always focus on water consumption. The price tag per gallon of water and the cost of disposing of the waste generated by the cleaning water are the main factors. Therefore, we note that the view that “more water is better” is not entirely acceptable for improving the quality of cleaning water.