Caig Laboratories DeoxIT Rosin Soldering Flux 8g

DeoxIT Rosin Soldering Flux, RSF R-80, is a resin-based flux that has a gel-like consistency at room temperature. It is non-conductive, even in humid environments. The practical syringe makes it easy to get the flux in place, without spillage.
Flux is a very important component in all soldering. The flux removes the oxide that is almost always present on the surface of the metal and prevents the formation of new oxide during the soldering process, which gives the solder better adhesion to the base metal. Almost all solder also includes flux to ensure that the tin adheres well to the base metal during the soldering process.

The flux makes it easier for the soldering tip to heat up the base metal and wet the solder joint, which is why it is easier to get a good solder if you start with a little fresh solder on the soldering tip, but this is nothing compared to how easy it is to solder if you instead put a little flux on the metal to be soldered. When heat is applied, the flux is activated, penetrating all the nooks and crannies of the future joint and preparing it for the tin.
Flux should be used when soldering thick cables or soldering cables to large, solid connectors that normally absorb a lot of heat.