Originally Posted by lost_asiangirl
Would someone mind explaining what flux is?
I really appreciate the help!
Flux is an acid that you put onto copper to make the smooth surface a bit more porous. It's kind of like taking sandpaper to a piece of plastic before you glue it to something.... The rougher surface of the copper will suck in the solder and make a much better joint, and it'll be tons easier to solder together as well.
Whenever you cut that LED tape (there are specific cut lines, as I'm sure you know) you have to solder wires onto the little copper pads on the tape. Those little pads, in my experience, don't like to be soldered onto unless you put on a little flux first. Once the flux is there, it's easy. Heat up the pad, put a little solder onto it. Heat up the wire, put a little solder onto it. Put the wire and the pad together, heat them both up, the solder will melt together (add a little if needed) and boom, you have a solder joint.