Fluxing residue

It is sometimes necessary to remove flux residues after processing due to their corrosive nature. This can be an added source of variability. 

Although inhibitors are deliberately added to the silicone formulation to control cure rate, unwanted cure inhibition can be caused by other species that react to form strong complexes with the platinum catalyst. Most notable of these undesired inhibitors include organotin and other organometallic compounds, sulfur, polysulfides, polysulfones or other sulfur-containing materials, amines, urethanes or amine-containing materials, unsaturated hydrocarbons in plasticizers, and some solder flux residues. 

For optimum corrosion resistance it is recommended that similar composition fillers be used wherever possible, and obviously any flux residues that may be present must be removed. 

Trichlorotrifluoroethane (CFC 113) was widely used in the electronics industry for the removal of soldering flux residues from printed circuit boards, for degreasing components in the precision engineering industry, and for the dry cleaning of garments. 

The mixture is sintered in the range of 1100-1200 °C in nitrogen atmosphere. After elimination of the flux residue by acid washing. 

An interesting combination of methods is the polysulfide flux method, which can be usedforthe preparation of Ln202S (Ln trivalent rare-earth ion)-based luminescent materials (e.g. Y202S Eu or Gd202S Pr) [5.228]. In this method, the mixed oxides of the metals are mixed with excess sulfur and an alkali metal carbonate. On heating, the alkaline carbonate decomposes and reacts with sulfur to form a Uquid polysulfide flux. The oxides react with the polysulfide flux to form the oxysulfide. Flux residues can be removed by washing the reaction product in water. 

Precision cleaning of electronic parts in removing no-clean and rosin flux residues in vapor degreasing and cold cleaning... 

Hand wipe and immersion N/A cleaning for removal of no-clean water soluble and rosin solder paste, white residue associated with isopropanol cleaning, and flux residues... 

Spray batch and spray in-line cleaning systems for OA, no-clean, and RMA pastes and lead-free flux residues Removes all types of flux residues including lead-free in batch washing Flux residue removal in ultrasonic immersion cleaning systems requiring no sump side additives... 

Dual tank system for stencil (29 inch maximum) and pallet cleaning RA, RMA, no-clean synthetic and water soluble (OA) flux residues, solder paste (ambient), and wet SMT adhesives (38-43 °C, ultrasonics)... 

Alpha 564M and 565 are functionally azeotropic blends of a chlorinated solvent and a polar component, designed for effective cleaning of post-soldering flux residues from pcb s and other electronic assemblies. Both formulations have no flash points. Compared to the fluorocarbons, they are more aggressive, more effective cleaners, yet lower in cost. 

Alpha 1001 and 1003 are azeotropes of Fluorocarbon 112 (tetrachlorodifluoroethane) and polar alcohols formulated for effective cleaning of postsoldering flux residues from pcb s and other electronic assemblies. Compared to chlorinated solvents, they are less aggressive and can be used on normally solvent-sensitive plastic materials. They are more effective solvents than Fluorocarbon 113 (trichlorotrifluoroethane)-based products, because of the extra chlorine atom. 

Vertrel SMT Is a proprietary azeotrope-like blend of Vertrel XF hydrofluorocarbon with trans-1,2-dichloroethylene and methanol. It is ideally suited for use in vapor degreasing equipment with soivency power for cieaning ionic soils and flux residues from electronic assemblies, it can also be used for precision and general industrial cleaning where this enhanced solvency is required. Vertrel SMT is nonflammable, has zero ozone depletion potential, and has low global warming potential. It can replace CFC-113, 1,1,1-trichloroethane (1,1,1-TCA), hydrochlorofluorocarbon (HCFC), and perfluorocarbon (RFC) fluids in many applications. 

Vertrel XMS is a proprietary azeotrope-like blend of Vertrel XF hydrofluorocarbon with trans-1,2-dichloroethylene, cyclopentane, and methanol. It is ideally suited for use in vapor degreasing equipment with solvency power for cleaning ionic soils and flux residues from electronic assemblies. 

An active flux chemically removes the oxide film, has an acid base, and is highly corrosive. These fluxes are usually hydrochloric acid in which zinc has been dissolved to form zinc chloride, known as killed spirits . Any joint prepared using an active flux must be thoroughly washed in warm water when soldering is completed, to remove any flux residue. For this reason an active flux is not suitable for electrical applications. 

The contamination that must be removed after the soldering process is predominantly from flux residues. The removal of flux residues from the soldered assemblies (6) is generally the most critical application. Thus it is the important fliat the assemblies are cleaned. A subsequent coating process demands a very clean and residue-free surface to assure long term stability of the coating against environmental stresses such as humidity. ... 

There is a large number of products on the market that are mixtures of water and water-soluble organic solvents. These media are recommended for the removal of solder paste, SMT adhesives and flux residues from stencils, misprints and populated reflowed PCBs."... 

The substrates that have to be eleaned should be free of all kinds of residues that might have some negative influence on the functionality of the substrates. The eontamination consist predominantly of flux residues, solder paste or SMT adhesive. Another important aspect with respect to the cleaning result is the compatibility between substrates and the cleaning chemistry. It is painless to remove the contamination while destroying the substrates. 

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