What is the No Clean Flux?
Most people will clean the PCB board when using solder paste contained rosin flux as electronics cleaning is largely applied in PCB industry, but few people will clean those using no clean solder paste. No clean solder paste was created to eliminate the need for further post-solder cleaning of circuit boards.
No clean fluxes are now the most popular fluxes to clean in electronics manufacturing. However, the flux residues left behind by no-clean pastes are more challenging to remove from PCBs than other fluxes, and the residues from no clean products can be left on the board in unwanted areas with detrimental effects on the PCB.
Reasons why it is necessary to remove no clean residues from PCB boards are as follows. First of all, no clean fluxes were developed as tacky resins which inherently coated and stuck to all surfaces. The residue would gradually build up on the test pins, and interfere with signal transmission in most instances.
Secondly, no clean fluxes can inhibit proper adhesion of conformal coatings. No clean flux residues can absorb moisture in process which will cause incomplete conformal adhesion, and this will allow corrosive materials, carbon dust build-up, corrosion, signal transmission problems, component failure, etc.
In general, no clean fluxes can be extremely difficult to clean particularly following any reflow processes as they can be baked on and tough to remove. So in applications where cleanliness is critical, it is important to consult your manufactures for the most effective, board-safe cleaning technology, otherwise, you’ll have a big headache.