Types of mig welding machine fluxes
Fluxes are chemical (liquid, solid, or gaseous materials) that remove oxide layers from the base metal and solder. Fluxes are used in soldering to remove such films and to protect the surfaces against reoxidation during soldering. There are various types of flux according to chemical makeup.
Types of mig welding flux:
Fluxes can be categorized by their chemical makeup:
- rosin-base fluxes
- organic fluxes
- inorganic fluxes
- synthetically activated fluxes (resins)
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- Water-white rosin dissolved in a suitable organic solvent is the closest model of a flux with noncorrosive residue. Rosin fluxes possess important physical and chemical properties that make them particularly suitable for use in the electrical industry.
- They are solid and inactive chemically at room temperature, but at soldering temperatures they gain sufficient activity to remove weakly adherent oxides from the noble metals gold and silver, as well as copper.
Nonactivated Rosin Flux:
- Although its noncorrosive nature has led to its widespread use in microelectronics, rosin base flux is lacking in chemical activity, which essentially limits its use to precleaned parts and to only a few metals that do not have adherent oxides.
- The active constituent, abiotic acid (C20H30O2), with a melting point of 173 °C (343 °F), becomes mildly active at soldering temperatures ranging from 177 to 316 °C (350 to 601 °F). The residue is hard, nonhygroscopic, electrically nonconductive, and noncorrosive.
Mildly Activated Rosin Flux:
- The very low chemical activity of rosin-base flux can be countered by the addition of activators, usually organic acids or amines.
- The end product, rosin mildly activated (RMA) flux, is still essentially noncorrosive, but is sufficiently active to remove oxides more reliably than the rosin-base flux. In addition, the residues are noncorrosive. However, care must be exercised in cases of high-reliability applications.
- It is advisable to specify that these fluxes be halide-free, in order to ensure that specific safety requirements are met in critical components. Even so, cleaning is now required to remove the flux residue. Both polar and nonpolar solvents have been used. These RMA fluxes are preferred for military, telephone, and other high-reliability electronic products.
- Activated rosin fluxes were developed to provide more chemically active fluxes for mass-produced electronics, such as packaged components.
- Most mass-produced electronics are manufactured using RMA fluxes. The use of chlorides in these fluxes requires effective cleaning after soldering to prevent corrosion and electrical leakage, because the presence of chloride ions in flux residue makes it conductive.
- Because of the chemistry of the activators, a double solvent cleaning is normally required. Activated rosin fluxes are widely used in commercial electronics and in high-reliability applications where the residue can be completely removed after soldering.
- Inorganic acids and salts that are highly corrosive and extremely active compose this class of fluxes.
- In many instances, they are not acceptable for use on electronics, but are suitable for plumbing and industrial applications.
- Inorganic fluxes do enable the soldering of ferrous alloys and high-nickel alloys used in electronic packages and hermetic enclosures. The difficulty of chloride ion removal has led to the gradual abandonment of inorganic fluxes, even for tinning purposes.