“Cleaning” is often overlooked in the PCBA manufacturing process, with many considering it to be an unimportant step. However, ineffective cleaning during the initial stages of product application can lead to numerous problems in the long term, resulting in increased costs due to rework or product recalls. In the following, we will briefly explain the importance of PCBA cleaning.
PCBA (Printed Circuit Board Assembly)
During the production process of PCBA, various contaminants are introduced at each stage, leading to the accumulation of various deposits or impurities on the surface of the PCBA. These pollutants can degrade product performance or even render the product ineffective. For example, during the soldering of electronic components, solder paste and flux are used for assisting soldering, leaving residues containing organic acids and ions. Organic acids can corrode PCBA, while the presence of ions may cause short circuits, rendering the product ineffective. There are various types of contaminants on PCBA, which can be categorized into two main types: ionic and non-ionic. Ionic contaminants, when exposed to moisture in the environment and powered on, undergo electrochemical migration, forming dendritic structures that create low-resistance paths, thereby disrupting PCBA functionality. Non-ionic contaminants can penetrate the insulation layer of the PCB and grow dendrites beneath the surface layer of the PCB. In addition to ionic and non-ionic contaminants, there are particulate contaminants such as solder balls, floatings in solder reservoirs, dust, and debris, which can lead to various defects during soldering, such as reduced solder joint quality, solder balling, voiding, and short circuits.
Among so many contaminants, which ones are the most concerning? Flux or solder paste is commonly used in reflow soldering and wave soldering processes. They mainly consist of solvents, wetting agents, resins, corrosion inhibitors, and activators. Residues left after soldering inevitably contain thermally modified substances, which are the predominant factors affecting product quality among all contaminants. Residues left after soldering are the most significant influencing factors on product quality. Ionic residues are prone to causing electrical migration, leading to a decrease in insulation resistance. Rosin residues are prone to adsorbing dust or impurities, leading to an increase in contact resistance and, in severe cases, causing open circuits. Therefore, strict cleaning after soldering is necessary to ensure the quality of PCBA. In conclusion, PCBA cleaning has become extremely important. “Cleaning” is a crucial step that directly affects the quality of PCBA and is indispensable.
