Techniques Used For Cleaning Assembled Circuit Boards
Cleaning Assembled Circuit Boards
While proficient engineers may employ an array of sophisticated simulations and analytical tools to assess a circuit’s schematic intricacy, they are not immune to the perils posed by impurities and accretion. As such, PCB cleaning remains a key practice that prevents ionic contaminants from sabotaging the reliability, effectiveness and longevity of a device’s functionality.
PCBs become contaminated during assembled circuit board and manufacturing processes with a variety of different substances, including solder residues, hand sweat, salts and acids, colophony or resin, fingerprints and oxides. These contaminates can interfere with the soldering and bonding of components, as well as cause etching issues that lead to shortened lifespans.
The most common method of removing ionic contaminants from assembled circuit boards is to use a solvent with polarity that can dissociate other ions and dissolve them. Solvents commonly used include isopropyl alcohol (IPA), acetone and baking soda. These cleaners should be applied sparingly, and the dissolved particles carefully removed from the board with a clean cotton swab or lint-free towel.
Techniques Used For Cleaning Assembled Circuit Boards
A final rinse is a crucial part of the PCB cleaning process to ensure that all residual IPA/DI solution has been completely eliminated from the board’s surface and all loosened debris is flowing off of the board. This step can be done with potable water or deionized water.
Several techniques are employed during this phase of the PCB cleaning process, and the best approach is often dependent on the type of contamination being addressed. Those who are tackling water-soluble flux residues may benefit from an ultrasonic cleaning solution, which utilizes sound waves to break down and remove the contaminants. This technique is also an effective method for removing non-soluble materials, such as solder mask, adhesives and coatings.
Conversely, those attempting to dislodge volatile, ionic materials such as salts and acids from the surfaces of a board should consider using a gas phase cleaning machine. This method boils a chemical solvent to create steam that can effectively displace the contaminants and wash them away with minimal effort. This method is ideal for those working with complex PCBs, since it can be used to reach parts of the board that a physical brush cannot.
The type of flux residue present on a printed circuit board can have a significant impact on the removal process. For example, no-clean fluxes, which are intended to remain on the board, tend to be more difficult to remove than R, RA and RMA residues, which can typically be removed with isopropyl alcohol and standard PCB cleaning solutions.
Another alternative to the above methods is automated cleaning, which can be performed on a conveyor system or by immersing the board in a batch of heated solvent or vapor degreaser. This approach can be especially useful for large-scale cleaning jobs, since it can significantly reduce the amount of manual labor that is required to handle multiple pieces of equipment at once.
