For electronics work, you’ll definitely need rosin core. The rosin acts as flux for the solder, allowing it to flow onto and attach to the metal. You can certainly use liquid flux/rosin ...

Solder paste consists of solder powder mixed with a thick flux material and is "printed" onto a PCB using a stencil. The flux serves as a temporary adhesive to hold components onto the board until the ...

Other drawbacks of using flux include potential contamination ... Many lead-tin solders contain a rosin core to improve flow and reduce oxidation. The burnt or clear residue surrounding new soldering ...