Flux is an important element of all solders (both paste and wire). Flux allows component leads to flow and moisten properly onto PCB pads. Flux leftovers can sometimes lead to contamination or perhaps even electromigration between component contacts (resulting in shorts) on the printed circuit board. High reliability systems like space, military as well as other fundamental applications - generally demand the cleaning of notable no-clean fluxes. PCB cleaning is highly needed for these types of PCBs. Salespeople at Restronics have years of expertise in various forms of flux cleaning... from high-volume batch cleaning machines to benchtop flux cleaning sprays and chemistry to eliminate flux residues. By evaluating the process in use and making proper recommendations for improvement, we can decrease the manual labor necessary for hand spray cleaning and generally improve cleanliness and dependability by employing 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 extremely effective, can be very dangerous for the environment and for humans. Due to increasing restrictions on solvents used in Vapor Degreasers, companies are switching from solvent based cleaning to aqueous based flux cleaning. Aqueous cleaners are often zero-discharge, which implies that no residue or wash solution goes to the drain; it stays in the equipment. Generally, wash chemistry is a combination of DI water and cleaning chemicals.
As part of PCB cleaning, the correct cleaning chemistry must match the nature of the soils (could be oils, flux residue, or other contaminants). The majority of people try to use a basic alcohol cleaner but it typically produces a white sediment and doesn’t eradicate flux. This is notably challenging when clients need to conformally coat the PCB. Most conformal coatings will not adhere appropriately unless the printed circuit board has been cleaned properly. Before applying conformal coatings to military and space applications, all flux residues should be removed and verified using an Ionic Contamination tester.