Why Clean "No-Clean" Fluxes?

No-Clean flux increased in popularity as it leaves behind little to no residue during the soldering process, compared to rosin or water soluble flux. This reduced the need for extensive cleaning of circuit boards after soldering, saving companies much time and cost, making it an ideal choice for many production line. 

The residue left behind from no-clean flux or paste is considered to be so little that it does not require cleaning in most cases, and the resulting electronic device or machine can still function with no disruptions. While the general consensus is that no-clean flux does not need to be cleaned, there are some situations in which cleaning is recommended to ensure optimal condition of your circuit board. 

Why clean No-Clean Flux?

  • No-clean flux with additives.
    Some no-clean flux contains additional activators that help with the removal of oxides to improve wettability. Such activators will leave behind corrosive residues that need to be cleaned off. 
  • For smooth application of conformal coating.
    The surface of the PCB becomes tacky after the no-clean flux dries off, causing dust or other contaminants to stick on the board. This can cause an uneven surface and affect the application and adhesion of the conformal coating. 
  • Prevent leakage of current.
    With components on the boards getting closer, the residue from no-clean flux may get trapped between the components and cause dendrite growths, especially if the residue is conductive or if contaminants are trapped within the residue. Solder balls or stray solder may also get trapped on the board, which can cause short circuits. 
  • Prevent moisture build-up.
    Moisture could be absorbed by the leftover residue and overtime cause damage to the board. 
  • For high-reliability boards.
    No all boards are used the same way - the medical, aviation or military industry requires boards that are held to high technical cleanliness standards as a single contaminant can have a drastic impact. 
  • For aesthetic appearances.
    No-clean flux still leaves behind visible residue on the board as the liquid dries/evaporates. This may be unsightly and may be removed for visual purposes. 
  • Build up of residue.
    Using no-clean flux on the same board or same area over and over again will lead to a build up of residue and thus should be removed to avoid damaging the board. 

For more information on whether no-clean flux is suitable for you, contact our sales team at sales@tokimeku.com for a discussion!

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