With the rapid development of PCB manufacturing technology, PCB cleaning technology must be constantly updated and developed. Various cleaning technologies emerge at the right moment have different advantages and disadvantages in the process of their use. This paper discusses the analysis and solutions of the problems that often occur in these PCB cleaning technologies.
1. White Spots:
One of the problems encountered after the formation of the cleaning process is that after the PCB is cleaned and dried, some white spots often appear on the surface of the components. This spot is a surface residue film and its formation reasons are as follows.
The surface of the residue is dissolved during the cleaning process, but because of the low solubility, and the cleaning method does not completely remove the dissolved residue. When the components are dry, the residue and the crystals of the non-ionic material form a white pollutant, called a white spot.
The solutions are as follows: choosing solutions with high concentration of cleaning solution can improve cleaning cleanliness, avoid repeated cleaning, improve cleaning efficiency, reduce labor costs and reduce equipment depreciation.
2. The Paint Layers of The Components fall off:
The external surface of the device is painted type, and the components in the previous process test were painted type and laser type, so the original process parameters and process cleaning materials are not applicable to this element. To solve this problem, a small amount of preservatives should be added to the cleaning solution to neutralize the corrosion of alkaline cleaning solution. In this way, additional cleaning tests must be carried out specifically for these surfaces or components identified as paint-spraying and easily destructible: the proportion of preservatives shall be allocated, the proportion of cleaning liquid shall be reformulated, the cleaning time and cleaning temperature shall be adjusted, and the cleaning process shall be suitable for such components. Solution: adding a small amount of preservatives.
3. Marks of Components Drop:
When cleaning, the dropping of marks of the components on the cleaning part often occurs. It is found that the device identification method for falling is usually ink, and we know that the solvent resistance of general ink is very poor. In the case that the device identification method cannot be changed or the device supplier is not replaced, the solution can only be started from the process. On the one hand, for the same variety specifications, different manufacturers supply components and the same· parts of the sample with different specifications and different batches of the same supplier are stored after cleaning under the same cleaning process specification, while some parts are well marked and some are washed out, we hope to find the reason from the supplier; On the other hand, the test results show that the seal component identification and shell paint drop have no influence on the performance index of components after cleaning, and the integrity of component identification can be exempted from inspection after cleaning. As a function of traceability, component identification can be replaced by product file and device location number.