Flux is an integral element of both wire and paste solders. Flux promotes the correct flow and wetting of component leads onto PCB pads. Flux leftovers can sometimes lead to contamination or perhaps even electromigration between component leads (causing shorts) on the printed circuit board. High reliability systems - space, military and some other fundamental ones - usually demand the cleaning of so-called “No Clean” fluxes. PCB cleaning is highly necessary for these types of PCBs. Salespeople at Restronics South Central have years of background in various forms of flux cleaning... from benchtop flux cleaning sprays to higher volume batch cleaning machines and chemistry to remove flux residues. By evaluating the current process and making relevant suggestions for improvement, we can decrease the manual labor required for hand spray cleaning and generally improve cleanliness and reliability by adopting a DI water-based batch cleaner with aqueous chemistry.
The majority of US manufacturers make high reliability PCBs, so flux cleaning is essential. Cleaning printed circuit boards with solvents, though very effective, can be highly dangerous for the planet and for users. Organizations are shifting away from solvent-based cleaning and toward aqueous-based flux cleaning due to rising limits on the solvents used in vapor degreasers. Aqueous-based cleaners are typically zero-discharge, which means no wash solution or residue is discharged; it remains in the equipment. In general, wash chemistry is a mixture of DI water and cleaning chemistry.
As part of PCB cleaning, the correct cleaning chemistry must match the nature of the soils (could include flux residue, oils, or other contaminants). Several people try to utilize a basic alcohol cleaner but it typically leaves a white residue and doesn’t remove flux. This is particularly problematic when clients need to conformally coat the PCB. Most conformal coatings will not adhere effectively unless the printed circuit board has been cleaned properly. All flux residues should be cleaned and verified using an Ionic Contamination tester before applying conformal coatings to military and space applications.