Label：PCBA Manufacturing, Non-ionic Pollutants, Ionic Residues
Nov 30, 202111520
"Cleaning" is often overlooked in the PCBA manufacturing process. Many people think that cleanup is not a critical step. However, with the long-term use of the product on the client side, the problems caused by the ineffective cleaning in the early stage have caused many failures, and the return of the product or the recall of the product has caused a sharp increase in operating costs. Now JRPanel takes you to learn about the role of PCBA cleaning on circuit boards.
The PCBA production process includes multiple process stages. PCBA will be polluted to different degrees at each stage, so various deposits or impurities will remain on the surface of PCBA. These pollutants can reduce product performance and even cause product failure. For example, in the process of soldering electronic components, manufacturers will use solder paste, flux, etc. for auxiliary soldering, and the residue produced after soldering contains organic acids and ions. Among them, the organic acid will corrode the circuit board, and the existence of electric ions may cause a short circuit and cause the product to fail.
There are many kinds of pollutants on PCBA, which can be classified into two categories: ionic and non-ionic:
Ionic pollutants contact the humidity in the environment, and electrochemical migration occurs after electrification, forming a dendritic structure, resulting in a low-resistance path, and destroying the function of the circuit board;
Non-ionic pollutants can penetrate the insulating layer of the PCB and grow dendrites under the surface of the PCB.
In addition to ionic and non-ionic pollutants, there are also granular pollutants, such as solder balls, floating points in the solder bath, dust, etc. These contaminants can lead to a variety of undesirable phenomena such as reduced solder joint quality, sharp solder joints during welding, pores, short circuits, and so on.
With so many pollutants, which ones are the most concerned? Flux or solder paste is commonly used in reflow soldering and wave soldering processes. They are mainly composed of solvents, wetting agents, resins, corrosion inhibitors and activators. These substances dominate all pollutants. From the perspective of product failure, post-weld residues are the most important factor affecting product quality. Ionic residues can easily cause electromigration and decrease the insulation resistance. The rosin resin residue is easy to absorb dust or impurities and cause the contact resistance to increase. In severe cases, it will lead to open circuit failure. Therefore, strict cleaning must be carried out after welding to ensure the quality of the circuit board.
In summary, the cleaning of PCBA is very important. "Cleaning" is an important process directly related to the quality of PCBA and is indispensable.