How does the white residue on the PCB come from?

Sometimes a PCB with a very good design ratio has white residue after solvent cleaning, which makes the overall aesthetics greatly reduce. Although this problem will not affect the normal usage of the PCB in the PCB production process, but often make the engineer headache, firstly, this white residue gives the impression that the pcb is already oxidized, and secondly the customer will think we used the old inventory board for him. It has caused explain to customers many times. I believe that many pcb factories and pcb engineers have encountered such extremely embarrassing situations. How did the white residue on the pcb board come from?

In this section FASTPCBA will discuss the common causes and processing techniques of white residue on PCB board with everyone!

Firstly, the biggest reason of white residue on your PCB substrate is that there is already a residue in the substrate of the PCB. A part of the flux is absorbed during the processing process, and then through soldered and cleaned,unsightly white residue formed, therefore, it is important to keep the substrate free of residue before soldering. The improper drying of the laminate also causes white residue to appear, which can be eliminated by washing with a solvent. In the processing of PCB boards, some copper-based oxidation inhibitor formulations used by SMT manufacturers are not compatible with the solvent formulations used by engineers, which is also an important cause of white residue. In the past, copper surface oxidation  main raw material is rosin, but water-soluble flux was used in the soldering process.

Therefore, the substrate after cleaning on the assembly line exhibits a white rosin residue. This problem can be easily solved by adding a halogenating agent during the cleaning process. When using rosin flux, the rosin is not easy to wash after the solder stays for too long time, which is one of the causes of white residue. In this case, the delay time between solder and cleaning should be shortened. So that this phenomenon can be avoided. In addition to the reasons mentioned above, it is also possible that the engineer used the old flux in the design process, and the flux will absorb the water in the air. In the case, white residual water stains are formed after the soldering process.If such a problem occurs, the flux needs to be replaced in time, and the white residual water stain formed can be eliminated by using a chemical solvent.

In the production process of the circuit board, pcb manufacturing is the most basic and most important part. The quality of smt processing and pcba are closely related to the quality of pcb board. Any detail error can ultimately affect the performance of the product.