During the PCB assembly process, solder paste and flux residue can form residual chemical substances, including organic acids and decomposable ions. Organic acids have corrosive effects, and residual ions on the solder pads may cause short-circuit faults. Moreover, these residues on the PCB are particularly dirty and do not meet the cleanliness requirements of customers. Therefore, cleaning the PCB is essential.
The necessity of cleaning PCBA circuit boards
The presence of contaminants on PCBs directly affects their appearance. Under high temperature and humidity conditions, residues may absorb moisture and become discolored. With the widespread use of leadless chips, micro BGAs, chip-level packaging (CSP), and 0201 components, the spacing between components and PCBs is continuously decreasing, and the assembly density is increasing. If halides are trapped under components or in areas that are difficult to clean, incomplete cleaning may lead to serious errors due to halide release. This can lead to dendritic growth and ultimately short-circuit faults.
Contamination can directly or indirectly pose potential risks to PCBs, such as:
- Organic acids in residues may corrode PCBs.
- Ions in residues may cause electrochemical migration between solder points during power-on, resulting in short-circuit faults.
- Residues can affect coating effectiveness.
- Over time and with changes in temperature, coating cracking and peeling may occur, leading to reliability issues.