When discussing the importance of the PCBA cleaning process, it involves various aspects such as cleaning methods, cleaning agents, and cleaning standards. User Zhang Min mentioned several instances where improper cleaning led to changes in device performance, such as reduced insulation performance of transformers and decreased contact performance of key switches. Recently, Zhang Min specifically observed the cleaning process on the production line to study the cleaning machines, cleaning agents, and cleaning guidelines used.
The purpose of cleaning PCBAs after soldering is to effectively remove organic and inorganic contaminants such as flux residues, water-soluble fluxes, and no-clean fluxes/flux residues from the surface of SMT/THT PCBAs.
Cleaning Methods:
- Manual Cleaning: It is suitable for cleaning small batches of PCBA samples. Chemical cleaning is performed in a constant temperature bath. When there are many components on the board that cannot be cleaned, selective cleaning can be achieved through manual cleaning. However, manual cleaning has the disadvantage of direct exposure to chemical solvents, which can be harmful to health.
- Equipment Cleaning: The Silman Tech PCBA cleaning machine DEZ-C758 is specifically designed for the removal of flux residues after wave soldering. It replaces manual scrubbing, improves cleaning capacity and cleanliness, and reduces cleaning costs. With multiple brushing processes, it efficiently removes flux residues on the PCBA after soldering without wetting the front-facing components. The unique combination of roller brush and disc brush thoroughly cleans from multiple directions, eliminating dead angles in cleaning and ensuring cleanliness. The fully automatic cleaning mode eliminates the need for operators to contact chemical liquids.
Cleaning Effect Evaluation Standards: After cleaning the PCBA board, its cleanliness needs to be evaluated to ensure product reliability and compliance with customer requirements. According to the standard SJ20896-2003, cleanliness of electronic products is divided into three levels based on reliability and performance requirements. After cleaning, the PCBA should not have dust, fibers, solder splashes, solder dross, white residues, fingerprints, etc., and there should be no whitening or darkening on the surface and solder joints.
PCBA Cleaning Requirements:
- During the cleaning process, metal tools such as tweezers should not directly contact the PCBA to avoid damaging or scratching the PCBA surface.
- After component soldering on the PCBA board, flux residue will undergo physical reactions causing corrosion over time. Therefore, cleaning should be done as soon as possible. Some companies require cleaning of boards to be done within 72 hours after board (DIP) soldering. For boards exceeding the controlled time requirement, the cleaning time needs to be extended.