Solder flux

Solder flux is a chemical substance used in soldering to clean and prepare metal surfaces for joining. It removes oxides from the surfaces to be soldered.

Flux comes in various forms, including paste and liquid.

Paste is generally preferred because it is easier to work with than liquid.

Paste can come in a tube syringe, and liquid flux can come in a flux pen.

Paste can also come in a jar, but this is hard to work with.