PCB Tech - What is the reason for the white residue on the PCB board?

SMT chip processing is an indispensable and important process for PCB board welding in the PCB circuit board production process. After the PCB circuit board is soldered, sometimes it is found that there are white residues on the PCB circuit board, which will affect the circuit board. It is beautiful, and may have a corresponding impact on the performance of the PCB circuit board and PCBA circuit board. Therefore, it is necessary to understand the causes of these white residues and deal with them in time.

The reasons for the white residue after soldering on the PCB circuit board and the treatment method are as follows:

1. The appearance of white residues on the PCB circuit board in the PCB factory patch processing is generally caused by the improper use of flux. Rosin flux often produces white spots during cleaning, and sometimes it will not be possible to switch to other types of flux. This phenomenon occurs.

2, if there are residues on the circuit board during production, white spots will occur after storage for a long time, and strong solvents can be used for cleaning.

3, the incorrect processing of the circuit board will also cause white spots. Often a certain batch of circuit boards will have problems, but others will not. For this phenomenon, use a strong solvent to clean it.

4, the flux was incompatible with oxidation maintenance. PCBA only needs to use another flux to improve the problem.

5, because the solvent in the manufacturing process degrades the raw materials of the PCB board, there will also be white residues, so the shorter the storage time, the better. The solution in the nickel plating process often causes this problem, which requires special attention.

6, the flux is used for a long time and aged, and it is exposed to the air to absorb water and form white spots. When using fresh flux, the solder stays for too long before cleaning.

Before smt technical operators do not use anti-corrosion paint, smt chip processing technical operators will also spray anti-corrosion paint on PCB circuit boards, and one time is enough, only three sprays, and the final coating produced is a bit thick. As high as 300 microns, if only the high thickness is just right, the appearance of the product is not very beautiful. In this case, there will be a certain adverse effect on the PCB board.

In fact, anti-corrosion coatings are thicker, waterproof, heat-insulating, and moisture-proof. This is not difficult to understand, so naturally there will be no negative effects on the PCB factory smt patch processing PCB circuit boards, such as oranges. The surface of the skin or foam is because the spraying process is not mastered. This can be completely improved and avoided. Of course, we do not approve of thick anti-corrosion coatings. The first is the cost issue. If a thin layer of anti-corrosion coating can meet the requirements, you What is necessary for spraying three or four layers? In addition, the thickness of the general PCB circuit board is standard. If the coating is too thick, the thickness of the PCB circuit board will not meet the standard. Therefore, in the case of cost and PCB circuit board standards Bottom, the three-proof paint is as thick as possible, and has no adverse effect on the PCB circuit board.