Whether the board should be cleaned before soldering depends on the condition of the board. Those boards coming directly from PCB manufacturing should be clean due to the safe quality control techniques used throughout the manufacturing process.Likewise, fully assembled boards delivered to the end user do not require any additional cleaning if they have been carefully packaged and shipped.
Flux is a cleaning agent that prepares the metal surface for soldering by removing oxides and impurities. Flux can be used in combination with the solder used or separately depending on the soldering process used. In addition to its cleaning ability, flux can help PCB assembly by changing the surface tension of the molten solder.
In fact, ideally, the board should not be handled before soldering.Preventing the board from coming into contact with human hands helps reduce or eliminate potential contaminants. Human contact can leave grease, dirt, and salt on the board and cause corrosion in exposed metal areas, affecting its solderability. Additionally, airborne dust, ink, tape, and condensation contamination can add to these difficulties. And in a mass production process, cleaning the circuit board prior to assembly may involve as much cost as the circuit board being assembled.So if it is a relatively clean circuit board, you can choose not to clean it, but if it is a used circuit board, you can properly clean it, and do not touch the circuit board with bare hands during the process to avoid secondary pollution.
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