Flux
This text is machine translated.
About flux
Flux is an auxiliary material in soldering technology that causes chemical reactions to the solder and the materials. They prevent the soldering surfaces from oxidizing before and during the soldering process and thus a firm connection would be endangered. Flux also prevents the inclusion of foreign substances in the solder connection and reduces the surface tension of the solder in order to have perfectly fitting contact surfaces for the connection during soldering.
Flux is applied to the pre-cleaned area of the later solder joint. The majority of flux is removed after soldering to prevent subsequent corrosion of these substances at the solder joint.
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How do flux work?
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What flux is available?
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What was to be observed when working with fluxes?
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Questions and answers
How do flux work?
Solder flux is applied to the contact surfaces of the workpieces and the solder before soldering. Wetting the solder joint with flux has a cleaning effect and prevents oxidation on the workpieces and the solder before and during the soldering process, thus preventing corrosion due to contact with oxygen during soldering in normal air environments. Flux also decreases the surface tension of the solder so that it can be flexibly integrated into the resulting compound.
Practical knowledge:
In addition to flux for soldering, such as those in our shop, there are also flux, which is used in melting operations, for example, in mining for ore extraction.
What flux is available?
Illustration of soldering water as a flux
Flux is available in different compositions. The selection depends on the materials to be soldered together. In addition, the temperature of the soldering process is important for choosing the right flux, because chemical processes depend on it during the soldering process and thus the effectiveness of the excipients.
The type identification of solder flux is carried out according to a system of letters and numbers:
- F at the beginning stands for flux. Then come a hyphen and two more letters.
- S or L are the second most important for heavy metals or light metals. They identify materials for which the flux is suitable.
- H or W in third place provides information about brazing or soft soldering, i.e. the desired soldering process.
- The figures behind them distinguish flux mainly in terms of temperature in the soldering process, but also in terms of their other chemical properties.
Practical advice
Precise overviews of the designations for flux can be found freely available on the Internet or in table books. Before you buy a flux, take a look at the specific product data sheet.
Research and production of novel fluxes is in full swing.
For example, halogen-free and water-soluble flux is available today, but not for all applications.
Some metals solder excipients contain activators that increase the concentration of free ions on the surface of the material and improve the alloy process.
The residues of acidic flux must be removed after soldering to prevent further reactions with the ambient air, which could otherwise cause corrosion at the connection point.
Melting flux partly results in chemically modified material at the solder was used, which could lead to undesirable changes in the conductivity or the inoperability of printed circuit boards in electronics. For this reason, flux with the label "No-Clean" is available for soft soldering of electronic components at room temperature, which react so little chemically that no cleaning of flux is necessary after soldering.
What was to be observed when working with fluxes?
Safety note: Flux is a chemical that contains hazardous substances in some cases. They should therefore only be handled with strict compliance with the safety instructions in the respective product data sheets. Hazardous vapors are generated when soldering with flux. Do not inhale them and ventilate them sufficiently, as this is where the greatest danger lies.
Although flux does not reach its full reactivity until the melting temperature in the soldering process, harmful effects can occur even at room temperature, for example through corrosive components that attack the skin and mucous membranes, and at higher concentrations also attack internal organs such as the liver.
Corrosive flux such as zinc chloride and ammonium chloride should be applied directly to the work pieces, as they can otherwise cause damage to other surfaces as highly reactive substances.
Practical advice
Store flux only in the original packaging and out of the reach of children and animals.
If you are refilling flux, immediately label the substance and the hazards it poses. Make sure that all containers are tightly closed to prevent vapors from escaping.
When working overhead, make sure that you cannot be hit by dripping, hot melted parts of the materials or the solder.
Questions and answers
What alternatives are available for the use of flux during soldering?
In large-scale industrial production, some are soldered under inert gas or vacuum atmosphere, so that no oxygen can lead to undesired oxidation and still no flux has to be used, as these would complicate and increase the production process.
What was Löthonig?
Löthonig® is a registered brand name for a flux, which is suitable for increased soldering temperatures and still contains little harmful ingredients. It is therefore very popular with hobbyists.
Is there a difference between flux and flux?
No, fluxing means with ß is only the spelling in old German spelling, which is still found in many books older printing date and is still used by so many skilled craftsmen.