Soldering oil, also commonly referred to as flux, plays a key role in the PCB manufacturing and electronics assembly process. It is a chemical used in the soldering process that aids and facilitates the soldering process while providing a protective effect and stopping oxidizing reactions.

Properties:

Chemical Composition:
Soldering oils usually consist of rosin, resins, halide-containing active agents, additives and organic solvents.
Activity:
Soldering oils contain active agents that help remove oxides from the surface of the solder and the base metal being soldered.
Thermal Stability:
Soldering oils should have good thermal stability and not decompose as a result of elevated temperatures during the soldering process.
Reduced Surface Tension:
Soldering oil can reduce the surface tension of the molten solder, improve the wetting properties, and promote the flow of solder.
Residue Properties:
The residue of soldering oil should be easy to clean, non-corrosive, and will not cause a short circuit or degradation of insulation after soldering.
Safety:
Soldering oil should be non-toxic and without strong irritating odor to ensure the safety of operators.

Role:

Aids Heat Transfer:
Soldering oil accelerates the transfer of heat from the tip of the soldering iron to the solder and the surface of the object to be soldered.
Removes Oxides:
The active ingredients in the soldering oil can chemically react with the oxidized film on the metal surface to remove the oxidized film.
Prevents Re-oxidation:
During the soldering process, the protective layer formed by the soldering oil prevents re-oxidation of the solder joint and the base metal.
Improvement of Welding Quality:
Soldering oil can improve the aesthetics and reliability of the welded joints and reduce the occurrence of false and cold welding.
Protects the Base Material:
Welding oils quickly return to their role of protecting the weld metal from environmental influences and corrosion after welding.
Suitable for Different Welding Processes:
Soldering oils can be formulated to adjust to different soldering processes (e.g. manual soldering, wave soldering, selective soldering, etc.).
Environmentally Friendly:
Modern soldering oils tend to use environmentally friendly formulations to reduce the impact on the environment and human body.
No-clean Soldering Oils:
Some soldering oil formulations are designed to be no-clean, with minimal, non-corrosive post-soldering residues that do not require additional cleaning steps.

Choosing the right soldering fluid is critical to ensuring quality and productivity. At the same time, soldering fluids need to be selected with environmental and operator safety in mind.