Solder-flux residue removal

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 eomplete proeess in based on a closed-loop principle. Consequently, the cleaning process merely liberates those substances that are to be removed from the pe-boards (i.e., soldering flux residues). Closed-loop operation is not only advisable for eeologieal reasons, but is also a very sound economic proposition as it significantly minimizes process costs. 

The impact of Pb-free technology on wave soldering has largely occurred in the equipment performance. It has been determined that the same solder bath temperatures that are used for Sn-Pb processes (250 to 270°C) are suitable for the Sn-Ag-XCu Pb-free alloys. Therefore, excessive dross formation and flux residue removal have not become a significant problem during equipment operation. The lack of shiny fillets with the Sn-Ag-XCu alloys has been addressed by modified alloys having Ni and Ge additions that alter the solidification process, which leads to shinier fillet surfaces. 

Is Your Solder Pad Joining "Hairy" As part of a solder/flux/ cleaning procedure, the residue In Figure 10 (Insert) was produced. The residue consists of 6xl0pm leaf-like crystals on a ceramic substrate. The location of the residue prevented Its analysis In-sltu, so extraction replication(5) was used to remove some of the crystals for analysis by several small area techniques, as needed. Electron probe microanalysis showed lead, carbon and oxygen, which could Indicate many possibilities. 

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... 

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. 

Electrically conductive adhesives, primarily silver-filled epoxies, are finding uses as replacements for solder in surface-mounting components on printed-circuit boards and in flip-chip attachments. There are several driving forces for this application, a major one being the trend to eliminate lead and tin-lead solders because they may be health hazards. Also associated with the use of solder, is the need to eliminate ozone-depleting solvents presently used to clean and remove flux residues. Electrically conductive polymer... 

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